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1
Milus, Eugene A., Kevin D. Lee e Gina Brown-Guedira. "Characterization of Stripe Rust Resistance in Wheat Lines with Resistance Gene Yr17 and Implications for Evaluating Resistance and Virulence". Phytopathology® 105, n. 8 (agosto 2015): 1123–30. http://dx.doi.org/10.1094/phyto-11-14-0304-r.
Testo completoAbstract (sommario):
Stripe rust, caused by Puccinia striiformis f. sp. tritici, has been the most important foliar wheat disease in south central United States since 2000 when a new strain of the pathogen emerged. The resistance gene Yr17 was used by many breeding programs to develop resistant cultivars. Although Yr17 was classified as a seedling (all-stage) resistance gene conferring a low infection type, seedlings with Yr17 frequently had intermediate to high infection types when inoculated with isolates that caused little or no disease on adult plants of the same wheat lines. The objectives of this study were to determine how to best evaluate Yr17 resistance in wheat lines and to determine which factors made seedling tests involving Yr17 so variable. Stripe rust reactions on wheat seedlings with Yr17 were influenced by temperature, wheat genotype, pathogen isolate, and the leaf (first or second) used to assess the seedling reaction. The most critical factors for accurately evaluating Yr17 reactions at the seedling stage were to avoid night temperatures below 12°C, to use the first leaf to assess the seedling reaction, to use multiple differentials with Yr17 and known avirulent, partially virulent and virulent isolates as controls, and to recognize that intermediate infection types likely represent a level of partial virulence in the pathogen that is insufficient to cause disease on adult plants in the field.
2
Blaker, N. S., e J. D. Hewitt. "Comparison of Seedling and Mature Plant Resistance to Phytophthora parasitica in Tomato". HortScience 22, n. 1 (febbraio 1987): 103–5. http://dx.doi.org/10.21273/hortsci.22.1.103.
Testo completoAbstract (sommario):
Abstract Seedlings of 11 genotypes of tomato (Lycopersicon esculentum, Mill.) were inoculated at the first true leaf stage with zoospores of Phytophthora parasitica under controlled conditions and evaluated for resistance based on seedling death. The same lines also were transplanted into two fields naturally infested with P. parasitica and grown to maturity. Disease severity in the field was evaluated based on plant death and canopy collapse prior to harvest. Resistance to P. parasitica was present in both commercial lines and accessions of L. esculentum var. cerasiforme (Dun.) A. Gray. Seedling resistance was generally a good predictor of resistance in mature plants. The relative resistance and susceptibility expressed in seedlings was reflected in 10 of 11 genotypes in the field. One cultivar that was susceptible in the seedling test appeared resistant in the field. Expression of resistance in both the seedling test and field was influenced by environmental factors.
3
Abdelmalik, Abdelmalik M. "Enhanced Growth and Drought Resistance in Seedlings of Acacia tortilis due to Inoculation of Arbuscular Mycorrhiza Fungi and Bacillus subtilis". International Journal of Agriculture and Biology 26, n. 06 (1 dicembre 2021): 750–60. http://dx.doi.org/10.17957/ijab/15.1891.
Testo completoAbstract (sommario):
A shade house experiment was conducted in Saudi Arabia to evaluate the impact of a mixture of three arbuscular mycorrhiza fungi (AMF) namely Funneliformis mosseae, Rhizophagus intraradices and Claroideoglomus etunicatum, a bacterium Bacillus subtilis, and their combinations on the growth and drought resistance potential of Acacia torilis seedlings under moderate and water deficit-stress. Thus, inoculants treatments (AMF, Bacillus subtilis, AMF+Bacillus, and control) and several watering intervals (1, 2, 3 and 4 weeks) were applied. Inoculation of AMF and Bacillus to A. tortilis seedlings found effective in terms of improved seedling growth. AMF and combined inoculation resulted in a larger shoot (shoot fresh and dry weights, seedling height, leaf number, leaf area) and root development (root fresh and dry weights, root length, root surface area, and root volume) as compared to the non-inoculated seedlings. Single inoculants of B. subtilis, showed better improvement in 1- and 2-week watering intervals compared to the control. Inoculated seedlings showed lower proline accumulation than non-inoculated seedlings, and thus improved seedling resistance to water deficit-stress. Mycorrhizal and mixed inoculation enhanced the amount of chlorophyll in the seedling’s leaves. Furthermore, seedlings with AMF and co-inoculants showed better drought tolerance even at 3- and 4-week watering intervals. © 2021 Friends Science Publishers
4
Zhao, Wen Ju, Li Rong Wang, Hong Ji, Jian Shu Song e Yan Wei Fan. "Impacts of Plant Additive on the Seedling Bricks’ Physical Properties". Advanced Materials Research 518-523 (maggio 2012): 5401–5. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.5401.
Testo completoAbstract (sommario):
Homemade seedling bricks, which mixed and suppressed with the plant additive, clay, compost, slow-release fertilizer, can create a good living environment for plant growth, guide the development and growth of plant roots, achieve integration of bricks and seedlings to plant, and the seedlings transplant without time limit. We tested the molding density, shatter resistance, seepage rate and other physical properties of seedling bricks without plant additive, adding 5% and 10% of wheat straw, wheat shells and corn leaves, and the results show that adding plant additive can improve the physical properties of the seedling bricks effectively. The minimum density of the seedling brick contains 10% corn leaves, the minimum shatter resistance of the seedling brick contains 10% wheat straw, and the maximum seepage rate of the seedling brick contains 10% wheat straw.
5
Duchesne, Luc C., R. L. Peterson e Brian E. Ellis. "Interaction between the ectomycorrhizal fungus Paxillus involutus and Pinus resinosa induces resistance to Fusarium oxysporum". Canadian Journal of Botany 66, n. 3 (1 marzo 1988): 558–62. http://dx.doi.org/10.1139/b88-080.
Testo completoAbstract (sommario):
Inoculation of Pinus resinosa Ait. seedlings with the ectomycorrhizal fungus Paxillus involutus Fr. resulted in a 47% increase in resistance to subsequent infection by the root pathogenic fungus Fusarium oxysporum f.sp. pini as compared with control seedlings. This increase in seedling survival was associated with a sixfold decrease in the sporulation of F. oxysporum in the rhizosphere of seedlings inoculated with Pax. involutus when compared with the rhizosphere of control seedlings. Extraction and bioassay of the seedling rhizosphere and seedling tissues indicated that inoculation with Pax. involutus led to a fivefold increase in antibiotic activity in the rhizosphere of the seedlings treated with Pax. involutus. Most or all of the fungitoxicity was localized in the rhizosphere. Disease suppression by Pax. involutus in P. resinosa is, therefore, associated with an increase of fungitoxic chemicals in the rhizosphere of seedlings.
6
Lu, Pengxin, e Darren Derbowka. "Effects of seedling age on blister rust resistance assessments in eastern white pine and its hybrid backcrosses". Canadian Journal of Forest Research 42, n. 1 (gennaio 2012): 67–74. http://dx.doi.org/10.1139/x11-164.
Testo completoAbstract (sommario):
Seedling age at the time of artificial white pine blister rust ( Cronartium ribicola J.C. Fisch.) inoculation can affect the duration and accuracy of resistance assessments for eastern white pine ( Pinus strobus L.) and its hybrid backcrosses and thereby affect advances in breeding programs intended to enhance genetic resistance to the pathogen. Based on postinoculation seedling mortality rates, up to 5 years were required to rank resistance of eastern white pine genotypes when seedlings were inoculated with C. ribicola at 2 years of age compared with less than 2 years when they were inoculated after the first growing season. In this study, we evaluated and compared consistency of genotype rankings in seedling mortality rates between the two inoculation approaches. Assessment results from inoculating seedlings after the first growing season proved as reliable as those achieved by inoculating them after the second growing season. Inoculating seedlings at a younger age not only substantially reduced experimental time and costs but also allowed a larger number of seedlings to be screened for resistance, leading to higher experimental precision.
7
Bodnaryk, R. P., e R. J. Lamb. "Influence of seed size in canola, Brassica napus L. and mustard, Sinapis alba L., on seedling resistance against flea beetles, Phyllotreta cruciferae (Goeze)". Canadian Journal of Plant Science 71, n. 2 (1 aprile 1991): 397–404. http://dx.doi.org/10.4141/cjps91-055.
Testo completoAbstract (sommario):
Seedlings of Brassica napus L. 'Westar' or Sinapis alba L. 'Ochre' grown from seeds of various size were offered to flea beetles, Phyllotreta cruciferae (Goeze) in feeding tests for damage assessment. The proportion of cotyledon area damaged in both species was highest for seedlings grown from small seeds in choice and no-choice feeding tests. The proportion of seedlings killed by flea beetle feeding was also highest in seedlings from small seeds, an effect that was especially pronounced at high beetle densities (10/seedling) where 100% of seedlings from small seeds of B. napus were killed compared to 28.3% of seedlings from big seeds. For S. alba, at 20 beetles/seedling, 45.4% of seedlings from small seeds were killed compared to only 9.1% of seedlings from big seeds. Seedlings grown from big seeds of S. alba tolerated low levels of damage caused by flea beetle feeding or by scissors. No evidence for tolerance was obtained for seedlings from small seeds of S. alba or for seedlings from big or small seeds of B. napus. "Big seeds" appears to be a desirable trait that enhances crucifer seedling resistance to flea beetle attack and results in increased seedling survival. Key words: Brassica napus 'Westar', Sinapis alba 'Ochre', Phyllotreta cruciferae, flea beetle, seed size, resistance
8
Cséplö, M., M. Csösz, M. Gál, O. Veisz e G. Vida. "Seedling resistance to Stagonospora nodorum blotch in wheat genotypes". Czech Journal of Genetics and Plant Breeding 49, No. 2 (16 maggio 2013): 77–85. http://dx.doi.org/10.17221/69/2011-cjgpb.
Testo completoAbstract (sommario):
In two independent experiments set up in the greenhouse the seedling resistance to Stagonospora nodorum blotch was investigated in 92 varieties, breeding lines and genotypes with a known genetic background. The greatest area under the disease progress curve calculated from lesion type was 37.06, while in the case of the most resistant genotype this value was 0.38. Many of the lines and varieties bred in Martonvásár proved to have excellent resistance in terms of both percentage of infected leaf area and lesion type. Observations indicate that, depending on the aim of the experiment, the efficient selection of breeding lines is possible in the seedling stage either on the basis of the area under the disease progress curve calculated for lesion types, or on the basis of lesion types scored 7, 11 or 14 days after inoculation.
9
Putnik-Delic, Marina. "Resistance of some wheat genotypes to Puccinia triticina". Zbornik Matice srpske za prirodne nauke, n. 115 (2008): 51–57. http://dx.doi.org/10.2298/zmspn0815051p.
Testo completoAbstract (sommario):
Thirty-four wheat genotypes were tested for resistance characteristics to Puccinia triticina at different growth stages. At seedling stage in a greenhouse, latency period, infection frequency and reaction type were determined. In the field, time of spike appearance, and infection intensity were followed. Weak (r = 0.322) to strong (r = 0.660) correlation was found between resistance characteristics at seedling stage (LPxIFxRT, in the greenhouse) and in adult plants (infection intensity and AUDPC, in the field). The values of AUDPC (area under the disease progress curve) were also strongly related to resistance characteristics of seedlings (r = 0.598). As pseudoresistant in the field (especially equal to adult plant resistance) according to other stresses reactions were considered genotypes which were the most sensitive at seedling stage (20?C) and at adult stage they did not express maximal infection intensity, particullar Evropa 90 and Suvaca. Adult plant resistance as the sum of specific and pseudoresistance was observed on genotypes Tiha, Zlatka and Eva.
10
Admassu-Yimer, Belayneh, Tyler Gordon, Stephen Harrison, Shahryar Kianian, Harold Bockelman, J. Michael Bonman e Kathy Esvelt Klos. "New Sources of Adult Plant and Seedling Resistance to Puccinia coronata f. sp. avenae Identified among Avena sativa Accessions From the National Small Grains Collection". Plant Disease 102, n. 11 (novembre 2018): 2180–86. http://dx.doi.org/10.1094/pdis-04-18-0566-re.
Testo completoAbstract (sommario):
Accessions of cultivated oat (Avena sativa L.) from the United States Department of Agriculture–Agricultural Research Service Small Grains Collection in Aberdeen, ID were characterized for adult plant resistance (APR) and seedling resistance to crown rust, caused by Puccinia coronata f. sp. avenae. Initially, 607 oat accessions with diverse geographic origins were evaluated in field tests in Baton Rouge, LA. Of those, 97 accessions were not fully susceptible and were tested in the field in St. Paul, MN against a diverse P. coronata f. sp. avenae population. Thirty-six accessions that had some level of resistance in both field tests and mean coefficients of infection of ≤20 were further evaluated for APR and seedling resistance. Among these, four accessions (PI 193040, PI 194201, PI 237090, and PI 247930) were resistant to eight P. coronata f. sp. avenae races as seedlings. Twenty-nine accessions had resistance to at least one of the P. coronata f. sp. avenae races. Three accessions (CIav 2272, CIav 3390, and PI 285583) were fully susceptible to all eight P. coronata f. sp. avenae races as seedlings. Further evaluation of the three seedling-susceptible accessions at the flag leaf stage in a growth chamber resulted in moderately susceptible to moderately resistant responses. The resistance sources presented here may contain genes not deployed in elite oat varieties, and may be useful for future crown rust resistance breeding. The adult and seedling resistance found in accessions of the cultivated oat species is especially valuable because it avoids problems associated with the transfer of genes from wild species to cultivated oat.
11
CLOUTIER, Y., L. PELLETIER e R. MICHAUD. "DEVELOPMENT OF A TEST FOR FREEZING TOLERANCE IN YOUNG ALFALFA SEEDLINGS". Canadian Journal of Plant Science 70, n. 1 (1 gennaio 1990): 307–10. http://dx.doi.org/10.4141/cjps90-036.
Testo completoAbstract (sommario):
An experiment was conducted to study the effects of seedling age on their ability to harden, and to determine whether cultivar × seedling age interaction could be identified for frost resistance. In the present study, 6- to 24-d-old alfalfa (Medicago sativa L.) seedlings were significantly more freezing-tolerant after cold-hardening than unhardened controls. Cold-hardened seedlings of age varying from 8 to 24 d were hardier than 6-d-old seedlings. No cultivar × seedling age interaction was found. The best separation of the cultivars occurred between 18 and 24 d. These findings provide additional information towards the development of a rapid and reliable test for estimating freezing tolerance in alfalfa.Key words: Freezing test, alfalfa, cold hardiness, seedlings
12
Yücedağ, Cengiz, Nebi Bilir e Halil Barış Özel. "Phytohormone effect on seedling quality in Hungarian oak". Forest Systems 28, n. 2 (4 luglio 2019): e005. http://dx.doi.org/10.5424/fs/2019282-14604.
Testo completoAbstract (sommario):
Aim of study: to find out the effects of four phytohormones, including Indole Butyric Acid (IBA), Indole Acetic Acid (IAA), and Gibberellic acids (GA3, GA4) on seedling growth of Hungarian oak which has a natural distribution in the northwestern of Turkey.Area of Study: Mature acorns of Hungarian oak were collected from a natural stand in Zonguldak-Ereğli at northwestern region of Turkey.Material and Methods: Collected acorns of the species were pretreated with 300 ppm of each phytohormone for 24 hours and sown in Yenihan State Forest Nursery of Bartin, Turkey. Two years old bare-root seedlings were used for the measurements of seedling height, root collar diameter, stem, root and seedling fresh weights, and stem, root and seedling dry weights of two bare-root seedlings for each phytohormone treatment.Main results: Best performance of all studied seedling traits with the exception of root collar diameter was revealed in seedlings with IBA. In contrast, treatment of seeds with GA3 reduced all seedling traits apart from seedling height and root collar diameter. According to Dickson quality index, IBA was displayed to be the most beneficial phytohormone application for generating Hungarian oak seedlings with better mechanical resistance during transplanting.Research Highlights: IBA should be adopted in planting the seedlings of Hungarian oak for plantation activities.
13
Kolmer, J. A. "Virulence in Puccinia recondita f. sp. tritici Isolates from Canada to Genes for Adult-Plant Resistance to Wheat Leaf Rust". Plant Disease 81, n. 3 (marzo 1997): 267–71. http://dx.doi.org/10.1094/pdis.1997.81.3.267.
Testo completoAbstract (sommario):
Sixty-seven isolates of Puccinia recondita f. sp. tritici collected in Canada were tested for virulence to adult plants of Thatcher near-isogenic wheat lines with leaf rust resistance genes Lr13, Lr22a, Lr34, Lr35, and Lr13 and Lr34 combined. All of the isolates had low infection type to the Thatcher lines with Lr22a and Lr35. All isolates had lower infection type and lower rust severity on the Thatcher line with Lr34 compared with Thatcher. The isolates were polymorphic for virulence to the Thatcher line with Lr13; many isolates were completely virulent to this line, and other isolates produced very low or intermediate avirulent infection type. On the Thatcher line with Lr13 and Lr34 combined, many isolates had infection type and rust severity similar to the Thatcher line with Lr34, while other isolates had lower infection type and rust severity compared with the single-gene lines with Lr13 or Lr34. Fifteen isolates with low, intermediate, and high infection type to adult plants with Lr13 were tested for infection type on seedling plants of the Thatcher lines with resistance genes Lr13, Lr22a, Lr34, Lr35, and Lr37, and on Thatcher lines with Lr13 paired with seedling resistance genes. Most isolates were completely virulent to seedling plants with Lr13 and Lr22a. Plants with Lr37 expressed seedling resistance to all isolates tested. Seedling plants with Lr34 had lower infection types to all isolates compared with Thatcher. Seedlings with Lr35 had high infection types to most isolates, with varying amounts of chlorosis. The Thatcher lines with Lr13 plus seedling resistance genes were most resistant to the isolates that had very low infection types on adult plants with Lr13 and intermediate infection types on plants with seedling resistance genes. Genes Lr22a, Lr35, and Lr37 offer additional sources of highly effective leaf rust resistance in wheat.
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Saleem, Kamran, Mogens Støvring Hovmøller, Rodrigo Labouriau, Annemarie Fejer Justesen, Jihad Orabi, Jeppe Reitan Andersen e Chris Khadgi Sørensen. "Macroscopic and Microscopic Phenotyping Using Diverse Yellow Rust Races Increased the Resolution of Seedling and Adult Plant Resistance in Wheat Breeding Lines". Agronomy 12, n. 5 (28 aprile 2022): 1062. http://dx.doi.org/10.3390/agronomy12051062.
Testo completoAbstract (sommario):
We characterized yellow rust (YR) resistance in sixteen winter wheat breeding lines using three different pathogen races and macroscopic and microscopic phenotyping in lab and greenhouse. Three rust races were used on seedlings and two races on fifth and flag leaf growth stages. The wheat lines were previously characterized to possess none or different quantitative trait loci for YR resistance in field trials. At the seedling stage, twelve lines showed race-specific seedling resistance whereas four lines gave strong seedling resistance to all three races. Seven of eight lines with QTL.1B showed strong seedling resistance against the two races also used at fifth and flag leaves. Microscopic phenotyping of line NOS50906215 (QTL.1B) showed small fungal colonies stopped within 3 dpi associated with extensive hypersensitive response (HR). The lines NOS51014910 and NOS51014911 (QTL.3D alone) showed strong adult plant resistance (APR) from the fifth leaf stage. The lines NOS70140801 and NOS70140808 (QTL.3D + 7B) showed strong APR to one race but partial resistance to the other race at all growth stages. Microscopic phenotyping of line NOS70140801 (QTL.3D + 7B) showed more fungal growth and less HR against the race revealing strong APR compared to the one revealing partial resistance. Line NOS51010312 (QTL.7B alone) showed strong APR response against both races whereas line NOS51010313 (QTL.7B) was susceptible. A partial APR response was observed on line NOS51005019 (no QTLs reported). In conclusion, the approach of combining macroscopic and microscopic phenotyping and diverse pathogen races facilitates the identification of multiple and diverse seedling and adult plant resistance responses to yellow rust in wheat.
15
Kolmer, J. A. "Genetics of Leaf Rust Resistance in the Soft Red Winter Wheat Cultivars Coker 9663 and Pioneer 26R61". Plant Disease 94, n. 5 (maggio 2010): 628–32. http://dx.doi.org/10.1094/pdis-94-5-0628.
Testo completoAbstract (sommario):
Leaf rust, caused by the fungus Puccinia triticina, is an important disease of soft red winter wheat cultivars that are grown in the southern and eastern United States. The objectives of this study were to identify the leaf rust resistance genes in two soft red winter wheat cultivars, Coker 9663 and Pioneer 26R61, that have been widely grown and were initially highly resistant to leaf rust. Both cultivars were crossed with the leaf-rust-susceptible spring wheat cv. Thatcher and the F1 plants were crossed to Thatcher to obtain backcross (BC1) F2 families. In seedlings, the Thatcher/Coker 9663 BC1F2 families segregated for three independent seedling resistance genes when tested with different leaf rust isolates. The leaf rust infection types of selected BC1F3 lines, when tested with different leaf rust isolates, indicated that seedling resistance genes Lr9, Lr10, and Lr14a were present. In field plot tests, BC1F4 lines that were seedling susceptible had some adult plant resistance to leaf rust. Seedlings of the Thatcher/Pioneer 26R61 BC1F2 families segregated for two independent resistance genes. Infection types of selected BC1F3 lines indicated the presence of Lr14b and Lr26. The adult plant gene Lr13 was determined to be present in selected BC1F4 lines that were tested with different leaf rust isolates in greenhouse tests.
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Ballinger, DJ, e PA Salisbury. "Seedling and adult plant evaluation of race variability in Leptosphaeria maculans on Brassica species in Australia". Australian Journal of Experimental Agriculture 36, n. 4 (1996): 485. http://dx.doi.org/10.1071/ea9960485.
Testo completoAbstract (sommario):
Seedling and adult plant studies were used to identify the race structure of Leptosphaeria maculans (the cause of blackleg) on oilseed Brassica species in Australia. Host-pathogen interactions using a set of 12 differential host lines identified 14 seedling relationship, however, between seedling and adult plant reactions to individual isolates, indicating that seedling and adult plant resistance are under different genetic control. While non-specific adult plant resistance was observed in the B. napus line Jet Neuf, host-pathogen interactions confirmed the existence of race-specific adult plant resistances in other differential lines.
17
Gould, Nick, Tony Reglinski, Mike Spiers e Joe T. Taylor. "Physiological trade-offs associated with methyl jasmonate - induced resistance in Pinus radiata". Canadian Journal of Forest Research 38, n. 4 (aprile 2008): 677–84. http://dx.doi.org/10.1139/x07-193.
Testo completoAbstract (sommario):
Methyl jasmonate (MeJA) can induce defence responses in plants to pathogen attack, but it can also have consequences for plant growth. The transient effects of exogenous MeJA treatment on the resistance of Monterey pine ( Pinus radiata D. Don) seedlings to Diplodia pinea (Desm.) Kickx. and some physiological parameters affecting the impact of treatment on seedling growth were investigated. Following foliar application of 4.5 mmol·L–1 MeJA, disease resistance was greatest 1–2 weeks after treatment and declined with time thereafter. Elevated disease resistance was accompanied by a reduction in seedling growth rate the second week following MeJA treatment. Thereafter, seedling growth rate recovered and exceeded that of the control seedlings 4–5 weeks after MeJA treatment. Within hours of MeJA treatment, reductions in both the capacity of photosystem II and transpiration rate were observed, resulting in a concomitant reduction in net CO2 uptake rate. The slight reduction in transpiration rate was also associated with an increase in needle water potential. Longer term measurements showed no effect of MeJA on photosynthetic rate, transpiration rate, chlorophyll content, or shoot water potential and thus could not account for the elevated growth rate observed 4–5 weeks after treatment.
18
Ye, Long Hua, Qiu Jing Li, Li Xue, Gan Wen Lie, Xiao Li Hou e Hong Yue Chen. "Effects of Ozone and Drought on Physiological Characteristics of Three Seedling Types in South China". Applied Mechanics and Materials 522-524 (febbraio 2014): 1089–97. http://dx.doi.org/10.4028/www.scientific.net/amm.522-524.1089.
Testo completoAbstract (sommario):
Seedlings of Michelia macclurei, Cinnamomum camphora and Rhodoleiachampionii were placed in open-top chambers (OTC) with two ozonic treatments including E40 (nature air, 40 ppb) and E150 (150 ppb) and two water treatments. Physiological indexes such as chlorophyll, soluble sugar, soluble protein, proline, MDA and SOD of three seedling types were evaluated. With increasing experimental time, chlorophyll content generally decreased or remained steady, soluble sugar content increased followed by a decrease and SOD activity increased for the three seedling types in ozone treatment, drought treatment or ozone-drought intercross treatment. Contents of soluble protein and proline increased for the three seedling types in ozone treatment and drought treatment. The MDA content increased for M. macclurei and C. camphora in ozone treatment and drought treatment and for R. championii in the three stress treatments. Principal component analysis indicated that the resistance abilities of ozone, drought or intercross stress for the three seedling types was C. camphora seedlings > M. macclurei seedlings > R. championii seedlings.
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Zhu, Shuquan, Kurt J. Leonard e Heidi F. Kaeppler. "Quantitative Trait Loci Associated with Seedling Resistance to Isolates of Puccinia coronata in Oat". Phytopathology® 93, n. 7 (luglio 2003): 860–66. http://dx.doi.org/10.1094/phyto.2003.93.7.860.
Testo completoAbstract (sommario):
In our previous report, quantitative trait loci (QTL) for field adult plant resistance to crown rust were identified in an oat population of 152 F5:6 recombinant inbred lines from the cross of ‘Ogle’ (susceptible)/MAM17-5 (resistant). The objectives of the present study were to identify in the same population, the number, genomic location, and effect of QTL and digenic QTL epistasis associated with greenhouse seedling resistance to isolates of Puccinia coronata to determine if the QTL detected are isolate-specific and to compare them with previously detected QTL for field resistance. Reaction type was scored on greenhouse seedlings inoculated with three isolates. Composite interval mapping was conducted to identify genomic regions associated with resistance using a framework map of 272 molecular markers. Two QTL, Pcq1 and Pcq2, were identified for resistance to each of the three isolates. Pcq1, the major QTL controlling field resistance, did not confer detectable greenhouse seedling resistance when present singly; however, Pcq1 did serve as an enhancer of seedling resistance when it was combined with Pcq2. The final model explained 76.5, 77.9, and 79.3% of total phenotypic variation for resistance to isolates MNB248, MNB249, and MNB251, respectively. Race-specificity of quantitative resistance remains to be further examined.
20
Dranski, João Alexandre Lopes, Ubirajara Contro Malavasi, Marlene de Matos Malavasi e Douglass Frederick Jacobs. "Effect of ethephon on hardening of Pachystroma longifolium seedlings". Revista Árvore 37, n. 3 (giugno 2013): 401–7. http://dx.doi.org/10.1590/s0100-67622013000300003.
Testo completoAbstract (sommario):
Immediately after planting, tree seedlings face adverse environmental and biotic stresses that must be overcome to ensure survival and to yield a desirable growth. Hardening practices in the nursery may help improve seedling stress resistance through reduction of aboveground plant tissues and increased root volume and biomass. We conducted an assay to quantify changes in the morphogenesis following application of ethephon on seedlings of Pachystroma longifolium (Ness) I. M. Johnst.during hardening. The results showed no effect of the ethephon treatments on the number of leaves but a reduction of up to 50% in seedling height increment, and an increase in stem diameter increment of up to 44% with the 600 mg L-1 ethephon treatment, which consequently altered seedling Dickson Quality Index. Our results indicate that ethephon may help to promote desired morphological changes that occur during seedling hardening in nurseries.
21
Loughman, R., E. S. Lagudah, M. Trottet, R. E. Wilson e A. Mathews. "Septoria nodorum blotch resistance in Aegilops tauschii and its expression in synthetic amphiploids". Australian Journal of Agricultural Research 52, n. 12 (2001): 1393. http://dx.doi.org/10.1071/ar01034.
Testo completoAbstract (sommario):
A collection of 433 Aegilops tauschii was screened for response to infection with Stagonospora nodorum. Resistance similar or marginally superior to the range observed in spring wheat genotypes was readily identified. Three lines, RL5271, Aus18911, and Aus21712, were resistant to a range of pathogen isolates and were similar in resistance to a highly resistant French line, No.33. Accessions of Ae. tauschii assessed as resistant or susceptible as seedlings had corresponding reactions when tested as adult plants, with resistance being commonly expressed as restricted lesion development. Infection frequency differed between some Ae. tauschii lines. Seedling resistance in synthetic bread wheats was expressed partially or not at all depending on both the tetraploid and the tetraploid/Ae. tauschii combination. Assessment of adult responses among a range of synthetics showed occasional expression of moderate resistance around the level observed among reference bread wheat cultivars of similar maturity. Disease escape associated with late maturity was common. One synthetic wheat, #231, derived from a resistant Ae. tauschii, exhibited low adult disease expression associated with late maturity. This line was resistant in seedling tests and seedling resistance was dominant in F1 hybrids to bread wheat.
22
Herrera-Foessel, S. A., R. P. Singh, C. X. Lan, J. Huerta-Espino, V. Calvo-Salazar, U. K. Bansal, H. S. Bariana e E. S. Lagudah. "Yr60, a Gene Conferring Moderate Resistance to Stripe Rust in Wheat". Plant Disease 99, n. 4 (aprile 2015): 508–11. http://dx.doi.org/10.1094/pdis-08-14-0796-re.
Testo completoAbstract (sommario):
Stripe rust, caused by Puccinia striiformis f. sp. tritici W., is a devastating disease of wheat worldwide. A new stripe rust resistance gene with moderate seedling and adult plant resistance was mapped using an F5 recombinant inbred line (RIL) population developed from the cross of the resistant parent ‘Almop’ with the susceptible parent ‘Avocet’. The parents and RILs were phenotyped for seedling stripe rust response variation in a greenhouse and in field trials at Toluca, Mexico for 2 years. Almop showed moderate levels of resistance at both seedling and adult plant stages compared with the highly susceptible response of Avocet. The distribution of homozygous resistant, homozygous susceptible, and segregating RILs conformed to segregation at a single locus. Seedlings and adult plant responses were correlated, indicating that the same gene conferred resistance at both stages. A bulk segregant analysis approach with widely distributed simple sequence repeat (SSR) markers mapped the resistance gene to the distal region of the long arm of chromosome 4A. The SSR marker wmc776 cosegregated with this gene, whereas markers wmc219 and wmc313 were tightly linked and both located at 0.6 centimorgans. The resistance locus was designated Yr60.
23
Briggs, K. G., e G. J. Dunn. "Variation amongst Canadian six-row spring barley cultivars for germination and emergence characteristics in controlled environments and in the field". Canadian Journal of Plant Science 80, n. 2 (1 aprile 2000): 247–53. http://dx.doi.org/10.4141/p99-054.
Testo completoAbstract (sommario):
Information is lacking concerning the extent of variability in Canadian six-row barley cultivars for differences in potential field germination vigour and other germination characteristics, and the extent to which these traits can be predicted from laboratory tests. This study was conducted to evaluate the extent to which a genetically diverse range of Western Canadian six-row barley cultivars differ in germination resistance and early seedling vigour or emergence rate under controlled environments and in the field, over a range of temperature stress conditions. Vigour was assessed by measuring germination rate, emergence rate, and dry weight accumulation in young seedlings, in the growth cabinet and in the field. Cultivars studied were selected to represent a wide range of genetic diversity typical of Canadian breeding programs of the early 1980s. Growth cabinet assays were conducted at six temperatures from 2.5 to 20 °C. Field trials were conducted using the same cultivars seeded at three dates per site in 2 yr, to assess cultivar emergence rates and seedling dry weight accumulation over a range of seedbed temperatures, using two seed sources from cultivar increases each grown in different years.Cultivars differed significantly for germination resistance in the growth cabinet, and the performance of cultivars was relatively consistent across assay temperatures and for the two different seed sources. Differences among cultivars in growth for seedling dry weight were also consistent across temperatures, but cultivar performance for seedling dry weight accumulation was not significantly correlated with germination resistance in the cabinet test. In field trials, days to emergence were highly and significantly correlated with germination resistance determined in the growth cabinet. Germination resistance was less strongly correlated with dry weight accumulation in the field at 5 wk. Across cultivars, seedling dry weight estimates in the field were significantly correlated with seedling dry weights assayed in the growth cabinet. Results from this study confirm that genetic variation in potential germination rate and seedling vigour in the field can be identified in six-row barley using the germination resistance assay in the growth cabinet. Germination resistance identified more cultivar differences than were found for the seedling dry weight accumulation tests, which were characterized by high coefficients of variation and low correlation between growth cabinet and field. Key words: Temperature, field seedling vigour, barley cultivars, prediction tests
24
Moler, Ehren R. V., Keith Reinhardt, Richard A. Sniezko e Ken Aho. "First Report of Fungal Endophyte Communities and Non-Defensive Phytochemistry of Biocontrol-Inoculated Whitebark Pine Seedlings in a Restoration Planting". Forests 13, n. 6 (25 maggio 2022): 824. http://dx.doi.org/10.3390/f13060824.
Testo completoAbstract (sommario):
Plant endosymbionts (endophytes) influence host plant health and express genotype-dependent ecological relationships with plant hosts. A fungal species intended to confer host plant resistance to a forest pathogen was used as inoculum to test for effects of inoculation on disease resistance, microbiomes, and phytochemistry of a threatened pine species planted in a restoration setting. Correlations of inoculation presence/absence, phytochemistry, spatial location of seedlings, maternal seed sources, and fungal endophytic communities in the foliage of six-year-old whitebark pine (Pinus albicaulis) seedlings were assessed five years after an experimental inoculation of seedlings with foliar endophytic fungi cultured from whitebark pine trees at Crater Lake National Park, including Paramyrothecium roridum. We hypothesized that P. roridum would modify host microbiomes in a manner that combats white pine blister rust disease. Our assessment of seedlings in the field five years after inoculation allowed us to consider whether inoculation stimulated long-lasting changes in microbiome communities and whether effects varied by seedling genetic family. Tests for effects of endophyte inoculation on disease resistance were inconclusive due to current low levels of rust infection observed at the field site. Foliar fungal endophyte richness and Shannon diversity varied with maternal seed sources. Isotopic stoichiometry and phytochemistry did not vary with seedling spatial proximity, inoculation treatment, or maternal seed family. However, endophyte community composition varied with both seedling spatial proximity and maternal seed sources. Endophytic communities did not vary with the inoculation treatment, and the hypothesized biocontrol was not detected in inoculated seedlings. We draw three conclusions from this work: (1) fungal microbiomes of whitebark pine seedlings across our study site did not vary with host phytochemical signatures of ecophysiological status, (2) the inoculation of P. albicaulis seedlings with a mixture of fungal endophytes did not lead to persistent systemic changes in seedling foliar microbiomes, and (3) in correspondence with other studies, our data suggest that maternal seed source and spatial patterns influence fungal endophyte community composition.
25
Šņepste, Ilze, Baiba Krivmane, Vilnis Šķipars, Astra Zaluma e Dainis E. Ruņģis. "Induction of Defense Responses in Pinus sylvestris Seedlings by Methyl Jasmonate and Response to Heterobasidion annosum and Lophodermium seditiosum Inoculation". Forests 12, n. 5 (14 maggio 2021): 628. http://dx.doi.org/10.3390/f12050628.
Testo completoAbstract (sommario):
The induction of defense responses in Pinus sylvestris L. seedlings by methyl jasmonate (MeJA) was investigated in three experiments. Two different MeJA application methods were tested, and induction of defense responses was assayed by seedling inoculation with Heterobasidion annosum (Fr.) Bref. and Lophodermium seditiosum Minter, Staley and Millar. In the first experiment, five-year-old P. sylvestris ramets of one clone were directly treated with MeJA, followed by inoculation with H. annosum. In the second experiment, open-pollinated Scots pine seedlings were treated with MeJA by direct spraying and vaporization, and inoculation with H. annosum was done using a slightly modified protocol. In the third experiment, open-pollinated Scots pine seedlings were treated with MeJA by vaporization and inoculated with L. seditiosum. Direct application of MeJA induced seedling mortality, and in some cases, decreased resistance to inoculation with H. annosum. Application of MeJA by vaporization was less stressful for seedlings, and resulted in increased resistance to both H. annosum and L. seditiosum. In addition, an unforeseen Neodiprion sertifer (Geoffroy) and Hylobius abietis L. infestation provided anecdotal evidence of the efficacy of MeJA in inducing resistance to insect pests as well. Further studies are required on the induction of resistance to additional diseases and pests. Induced resistance could be used as a possible protective mechanism for Scots pine seedlings prior to planting during reforestation of stands to increase vitality and survival.
26
Hassan, J. A., Y. J. Zhou e J. D. Lewis. "A Rapid Seedling Resistance Assay Identifies Wild Tomato Lines That Are Resistant to Pseudomonas syringae pv. tomato Race 1". Molecular Plant-Microbe Interactions® 30, n. 9 (settembre 2017): 701–9. http://dx.doi.org/10.1094/mpmi-11-16-0247-r.
Testo completoAbstract (sommario):
Bacterial speck caused by Pseudomonas syringae has historically been controlled by the Pto/Prf gene cluster. Emerging strains like P. syringae pv. tomato race 1 overcome resistance conferred by Pto/Prf, and can cause serious crop loss under appropriate environmental conditions. We developed a rapid assay to screen wild tomato seedlings for resistance to P. syringae pv. tomato race 1. We established the seedling resistance assay using the well-characterized P. syringae pv. tomato race 0 strain, DC3000, which is recognized in tomato cultivars carrying Pto/Prf (PtoR) and causes disease in isogenic lines lacking this cluster (PtoS). We optimized infectious conditions for P. syringae on tomato seedlings and demonstrated that tomato seedlings respond like adult tomato plants in critical measures of susceptibility and immunity, including the hypersensitive response, rapid ion leakage, restricted bacterial proliferation, and phenotypic resistance. After establishing infectious conditions for P. syringae pv. tomato race 1 on tomato seedlings, we screened 96 wild accessions and identified two accessions with strong P. syringae pv. tomato race 1 resistance, Solanum neorickii LA1329 and S. habrochaites LA1253, which are also resistant to bacterial infection as adult plants. This rapid high throughput seedling assay has many advantages, including reduced plant growth time and large sample sizes, and will allow for large-scale screening of resistance in tomato.
27
Babiker, E. M., T. C. Gordon, J. M. Bonman, S. Chao, M. N. Rouse, G. Brown-Guedira, S. Williamson e Z. A. Pretorius. "Rapid Identification of Resistance Loci Effective Against Puccinia graminis f. sp. tritici Race TTKSK in 33 Spring Wheat Landraces". Plant Disease 100, n. 2 (febbraio 2016): 331–36. http://dx.doi.org/10.1094/pdis-04-15-0466-re.
Testo completoAbstract (sommario):
Wheat breeders worldwide are seeking new sources of resistance to Puccinia graminis f. sp. tritici race TTKSK. To prioritize field-resistant landraces for follow-up genetic studies to test for the presence of new resistance genes, seedling response to P. graminis f. sp. tritici race TTKSK, molecular markers linked to specific Sr genes, segregation ratios among progeny from crosses, and bulked segregant analyses (BSA) were used. In total, 33 spring wheat landraces with seedling resistance to P. graminis f. sp. tritici race TTKSK were crossed to a susceptible genotype, LMPG-6. The segregation ratios of stem rust reactions in F2 seedlings fit a single dominant gene model in 31 populations and progeny from two crosses gave ambiguous results. Using the 90K wheat single-nucleotide polymorphism genotyping platform, BSA showed that the seedling resistance in 29 accessions is probably controlled by loci on chromosome 2BL. For the three remaining accessions, BSA revealed that the seedling resistance is most likely controlled by previously unreported genes. For confirmation, two populations were advanced to the F2:3 and screened against P. graminis f. sp. tritici race TTKSK. Segregation of the F2:3 families fit a 1:2:1 ratio for a single dominant gene. Using the F2:3 families, BSA located the TTKSK locus on chromosome 6DS to the same location as Sr42.
28
Erb, W. Alan, Arlen D. Draper e Harry J. Swartz. "Screening Interspecific Blueberry Seedling Populations for Drought Resistance". Journal of the American Society for Horticultural Science 113, n. 4 (luglio 1988): 599–604. http://dx.doi.org/10.21273/jashs.113.4.599.
Testo completoAbstract (sommario):
Abstract Open-pollinated species, interspecific hybrid seedling populations, and selected clones propagated by softwood cuttings and tissue culture were used to further evaluate the use of dry soil to screen blueberry seedlings for drought resistance. These different propagation types of Vaccinium (subgenus Cyanococcus) were screened for drought resistance in a Galestown fine sandy loam soil. The soil was permitted to dry to progressively higher soil tension levels to a maximum of 0.8 MPa. The plants were evaluated by scoring them on a 1 to 9 shoot damage rating scale and by determining the fraction of total biomass partitioned as roots. Drought resistance in blueberries is heritable and there is a high degree of genetic diversity within and among Vaccinium spp. for resistance to water deficits. Southern species (Vaccinium darrowi Camp, V. elliottii Chapman, and V. ashei Reade) were more drought-resistant than northern species (V. corymbosum L., V. vacillans Torrey, and V. myrtilloides Michaux), which demonstrated the reliability of this soil screening method. Clones with half their germplasm from southern species were usually drought-resistant. This screening method can be used to select for shoot and root vigor and drought resistance in 6- to 7-month-old blueberry seedlings.
29
Robert, Emilie, Suzanne Brais, Brian D. Harvey e David Greene. "Seedling establishment and survival on decaying logs in boreal mixedwood stands following a mast year1This article is one of a selection of papers from the International Symposium on Dynamics and Ecological Services of Deadwood in Forest Ecosystems." Canadian Journal of Forest Research 42, n. 8 (agosto 2012): 1446–55. http://dx.doi.org/10.1139/x2012-085.
Testo completoAbstract (sommario):
In the boreal forest, establishment of tree regeneration is tightly linked to both mast years and the availability of adequate germination beds for seedlings. We took advantage of a mast year (2006) in the eastern boreal mixedwood to compare seedling establishment in 2007 and seedling survival 2 and 4 years later on sections of fallen logs and equivalent areas of adjacent forest floor. Several factors that could explain establishment of seedlings on logs were measured, including wood resistance, density, moisture content, and C/N ratio. Our results show that small-seeded species, such as white birch ( Betula papyrifera Marsh.) and white spruce ( Picea glauca (Moench) Voss), establish preferentially on logs whereas balsam fir ( Abies balsamea (L.) Mill.), a relatively large-seeded species, establishes more often on the forest floor. Using logistic regressions, we confirmed that the probability of seedling establishment on logs declines with wood resistance, while the survival probability is inversely proportional to stand deciduous basal area. Survival rate was similar for seedlings established on the forest floor and on logs. However, none of the white birch seedlings established on the forest floor in 2007 were alive by 2011. Even following an exceptional mast year, log occurrence in eastern mixedwood stands would not suffice to obtain adequate white spruce stocking levels.
30
Franke, M. D., T. B. Brenneman e C. C. Holbrook. "Identification of Resistance to Rhizoctonia Limb Rot in a Core Collection of Peanut Germ Plasm". Plant Disease 83, n. 10 (ottobre 1999): 944–48. http://dx.doi.org/10.1094/pdis.1999.83.10.944.
Testo completoAbstract (sommario):
Diseases caused by Rhizoctonia solani lead to significant reductions in peanut yields and quality throughout the world. A subset of accessions from the peanut germ plasm core collection plus the commercial cultivars Florunner, Southern Runner, Georgia Browne, and Georgia Green were evaluated for resistance to limb and seedling hypocotyl infections caused by R. solani. Georgia Green and core accessions 95 (PI 497351), 197 (PI 331326), 208 (PI 274193), 244 (PI 343361), 246 (PI 343398), and 524 (PI 288178) had levels of resistance comparable to Georgia Browne, the only commercial cultivar reported to have partial resistance to Rhizoctonia limb rot. Eleven core accessions, representing the full range of disease expression, and the commercial cultivars were evaluated in growth chambers to quantify their susceptibility to seedling hypocotyl infections and to determine if evaluating seedlings could serve as a primary screening method to identify potential sources of limb rot resistance. The most resistant core accessions to seedling hypocotyl infections were 234 (PI 159664) and 366 (PI 268968), and the most resistant commercial cultivar was Georgia Green. There was not a significant correlation between resistance to limb rot in the field and the severity of hypocotyl infections in growth chambers, indicating that resistance to hypocotyl infections is not a good indicator of resistance to Rhizoctonia limb rot.
31
Ni, Ming, Zhenzhou Gao, Hong Chen, Chen Chen e Fangyuan Yu. "Exponential Fertilization Regimes Improved Growth and Nutrient Status of Quercus nuttallii Container Seedlings". Agronomy 12, n. 3 (10 marzo 2022): 669. http://dx.doi.org/10.3390/agronomy12030669.
Testo completoAbstract (sommario):
Background: The conventional fertilization regime ignores the allometric characteristics of Quercus nuttallii seedlings, challenging them to meet the nutritional needs at each growth stage. This study was conducted to determine the impact of exponential fertilization on the growth and nutrient status of Q. nuttallii container seedlings. Methods: Two fertilization regimes (average/exponential) were performed on Q. nuttallii container seedlings, and varied gradients (0, 300, 500, 700, and 900 mg/seedling) of N supply were set for the two regimes. Result: N application promoted the seedling height, root collar diameter, total biomass, and N/P/K accumulation of Q. nuttallii, and the exponential fertilization obtained better effects in general. An appropriate amount of exponentially N application was beneficial to the growth of root system, whereas excessive dosages inhibited it. Judging from seedlings growth status and nutrient accumulation, 900 mg/seedling under exponential fertilization was adequate for Q. nuttallii seedlings. However, 500 and 700 mg/seedling under exponential fertilization may have advantages in improving seedlings’ stress resistance. Conclusions: Exponential fertilization did not only meet the nutrient requirements and promote the growth of Q. nuttallii seedlings, but also facilitated the root growth to indirectly accelerate the assimilation of N/P/K, therefore improving the afforestation quality.
32
Tang, Jiao, Carlos Alberto Busso, Deming Jiang, Ala Musa, Dafu Wu, Yongcui Wang e Chunping Miao. "Experimental sand burial affects seedling survivorship, morphological traits, and biomass allocation of <i>Ulmus pumila</i> var. <i>sabulosa</i> in the Horqin Sandy Land, China". Solid Earth 7, n. 4 (18 luglio 2016): 1085–94. http://dx.doi.org/10.5194/se-7-1085-2016.
Testo completoAbstract (sommario):
Abstract. As a native tree species, Ulmus pumila var. sabulosa (sandy elm) is widely distributed in the Horqin Sandy Land, China. However, seedlings of this species have to withstand various depths of sand burial after emergence because of increasing soil degradation, which is mainly caused by overgrazing, climate change, and wind erosion. An experiment was conducted to evaluate the changes in its survivorship, morphological traits, and biomass allocation when seedlings were buried at different burial depths: unburied controls and seedlings buried vertically up to 33, 67, 100, or 133 % of their initial mean seedling height. The results showed that partial sand burial treatments (i.e., less than 67 % burial) did not reduce seedling survivorship, which still reached 100 %. However, seedling mortality increased when sand burial was equal to or greater than 100 %. In comparison with the control treatment, seedling height and stem diameter increased at least by 6 and 14 % with partial burial, respectively. In the meantime, seedling taproot length, total biomass, and relative mass growth rates were at least enhanced by 10, 15.6, and 27.6 %, respectively, with the partial sand burial treatment. Furthermore, sand burial decreased total leaf area and changed biomass allocation in seedlings, partitioning more biomass to aboveground organs (e.g., leaves) and less to belowground parts (roots). Complete sand burial after seedling emergence inhibited its re-emergence and growth, even leading to death. Our findings indicated that seedlings of sandy elm showed some resistance to partial sand burial and were adapted to sandy environments from an evolutionary perspective. The negative effect of excessive sand burial after seedling emergence might help in understanding failures in recruitments of sparse elm in the study region.
33
Mandal, Subhankar, e Christopher S. Cramer. "Screening of USDA Onion Germplasm for Fusarium Basal Rot Resistance". Horticulturae 7, n. 7 (2 luglio 2021): 174. http://dx.doi.org/10.3390/horticulturae7070174.
Testo completoAbstract (sommario):
Fusarium basal rot (FBR) caused by Fusarium oxysporum f. sp. cepae (FOC) is a major threat to onion (Allium cepa L.) production and marketing worldwide. Finding new sources of FBR-resistance to develop synthetic cultivars is a priority for onion breeders. As there are no FBR-resistant short-day onion cultivars, 85 U.S. National Plant Germplasm System plant introduction onion accessions that originated from 23 different countries were screened for their FBR susceptibility. To compare FBR susceptibility of these accessions at their seedling and mature bulb stages, a susceptible check cultivar, NuMex Crimson, a partially resistant check cultivar, Serrana and its selected population, Serrana-sel, were included in the study. The seedling screening was performed after inoculating silica-sand media with a virulent FOC isolate ‘CSC-515’ at 1.0 × 104 macroconidia g−1 of sand. Each entry was evaluated twice in growth chambers, and percent survival was adjusted to the number of seedlings that germinated in the uninoculated trays. Mature bulbs produced in the field were screened by inoculating transversely cut basal plates with potato dextrose agar plugs containing spores of the same isolate at 3.0 × 104 macroconidia mL−1. FBR severity and incidence were then calculated after 20 days of incubation. Significant variation was found among the accessions for FBR-susceptibility (p < 0.001) at both the seedling and the mature bulb stages. Two sets of 18 accessions were identified either for their higher seedling survival or higher mature bulb FBR-resistance compared to the checks. Among them, PI 256326 (‘Baia Periforme’, the originator cultivar of ‘Serrana’) had a higher seedling survival than both the checks, and a lower mature bulb severity than the susceptible check. Another accession, PI 656956 (‘S015’), exhibited higher seedling survival than the susceptible check and a low FBR severity (4.3 on a 1 to 9 scale) and incidence (41.7%). These two accessions, which were known previously for their high intra-population heterogeneity and root or bulb resistance for FBR, respectively, show promise for incorporating FBR-resistance into short-day onion cultivars. The cultivar rankings could vary in future studies with a range of FOC isolates due to a high cultivar × isolate interaction as observed in past studies.
34
Milczarek, D., A. Przetakiewicz, P. Kamiński e B. Flis. "Early selection of potato clones with the H1 resistance gene – the relation of nematode resistance to quality characteristics". Czech Journal of Genetics and Plant Breeding 50, No. 4 (27 novembre 2014): 278–84. http://dx.doi.org/10.17221/114/2014-cjgpb.
Testo completoAbstract (sommario):
Breeding a new potato cultivar is a long-term process ending with a few elite individuals from initially large populations. Screening for resistance in the seedling and first clonal generations is a cost-effective and efficient way to reduce the time needed to create a new variety. Unlike the phenotypic assessment of resistance to nematodes, marker-assisted selection (MAS) can be applied at early stages of selection. The frequent question among breeders is about the impact of early selection for resistance on the agronomic value of finally selected resistant progeny. The study presents a relationship between the presence of markers TG689 and 57R and some agricultural traits in field grown seedlings and three successive vegetative generations. Both markers are linked to H1 gene, which confers resistance to the golden cyst nematode Globodera rostochiensis. Clones with these markers had higher total tuber and starch yield than those without the markers. A negative relationship between marker presence and quality was not observed.
35
Erb, W. A., A. D. Draper e H. J. Swartz. "Methods of Screening Blueberry Seedling Populations for Drought Resistance". HortScience 23, n. 2 (aprile 1988): 312–14. http://dx.doi.org/10.21273/hortsci.23.2.312.
Testo completoAbstract (sommario):
Abstract Two methods of evaluating seedling drought resistance in Vaccinium (blueberry) spp. were examined. Twenty interspecific populations were greenhouse-grown and either matric-stressed in a dry 1 sand : 1 soil medium or osmotic-stressed in a nutrient solution containing polyethylene glycol (PEG). In both tests, population means were separated statistically by shoot damage ratings. The correlation (r = 0.46) between the two tests was positive and significant. Progenies of clones JU64 and JU62, which are sister seedlings (V. myrsinites Lamark × V. angustifolum Aiton), were the most drought-resistant. The soil screening test appeared more accurate because it grouped populations with common parentage. These tests indicated that the progenies differ in genetic capacity to resist drought.
36
Geange, Sonya R., Meisha-Marika Holloway-Phillips, Veronica F. Briceño e Adrienne B. Nicotra. "Aciphylla glacialis mortality, growth and frost resistance: a field warming experiment". Australian Journal of Botany 67, n. 8 (2019): 599. http://dx.doi.org/10.1071/bt19034.
Testo completoAbstract (sommario):
Decreasing snow depth and earlier snowmelt in alpine regions are expected to expose plants to a greater range of thermal extremes. Thus, paradoxically, in addition to increasing mean temperatures, aseasonal frost is likely to emerge as a major determinant of plant survival and development under a warming climate. Through the use of open top chambers, we assessed the effects of simulated warming on seedlings of the alpine herb Aciphylla glacialis (F.Muell.) Benth, sourced from provenances that vary in thermal characteristics. We hypothesised that seedlings grown at elevated temperature would have reduced survival and lower freezing resistance, but that individuals that did survive would show increased growth. Further, we hypothesised that seedlings sourced from the lower-elevation sites, where temperatures are more variable, would exhibit lower mortality at warmed conditions than those from sites with narrower thermal ranges. Warmed conditions significantly increased seedling mortality but those that survived grew slightly taller than their ambient counterparts, with no impact on leaf production or photosynthetic efficiency. Although the warming treatment did not influence temperature minimums, which would have allowed us to assess the impact of aseasonal frosts, there was no effect on freezing resistance. Contrary to our expectations, there was little evidence of variation among provenances. Our results indicate that a warmer climate with more extreme events may lead to a reduction in seedling establishment and survival; however, seedlings that do survive and establish are unlikely to express any lingering detrimental effects.
37
Yuan, Zhiheng, Chuntian Wang, ShiPeng Li, Xiao Li e Fuju Tai. "Effects of different plant hormones or PEG seed soaking on maize resistance to drought stress". Canadian Journal of Plant Science 94, n. 8 (novembre 2014): 1491–99. http://dx.doi.org/10.4141/cjps-2014-110.
Testo completoAbstract (sommario):
Yuan, Z., Wang, C., Li, S., Li, X. and Tai, F. 2014. Effects of different plant hormones or PEG seed soaking on maize resistance to drought stress. Can. J. Plant Sci. 94: 1491–1499. Drought stress has a major impact on plant growth and productivity, and seed soaking is an important way to increase seedling resistance to drought stress. This study investigated whether drought hardening chemicals, such as polyethylene glycol (PEG), or plant growth regulators enhance plant drought tolerance. The effects of PEG and several plant hormones, such as indoleacetic acid, gibberellic acid 3, 6-benzylaminopurine (6-BA), on seed germination and seedling growth under drought stress were analyzed. The results revealed that seed soaking with 5×10−3 mg L−1 6-BA or 10% PEG improved maize seed germination parameters under drought stress, including seedlings dry weight, seed vigor and germination rate. In addition, some physiological indices, such as superoxide dismutase and catalase activities, soluble protein contents and malondialdehyde etc. in seedlings under drought stress were improved compared with the control. Therefore, the application of 6-BA or PEG as a seed soak treatment had a significant and synergistic effect on seed germination and seedling growth under drought stress. However, the PEG seed soak treatment maybe slightly lead to plant damage and then improved plant ability to acquire some resistance to stress, the 6-BA were not so.
38
Oelke, L. M., e J. A. Kolmer. "Characterization of Leaf Rust Resistance in Hard Red Spring Wheat Cultivars". Plant Disease 88, n. 10 (ottobre 2004): 1127–33. http://dx.doi.org/10.1094/pdis.2004.88.10.1127.
Testo completoAbstract (sommario):
Leaf rust, caused by Puccinia triticina Eriks., is the most common disease of wheat (Triticum aestivum L.) in the United States and worldwide. The objective of this study was to characterize seedling and adult plant leaf rust resistance in hard red spring wheat cultivars grown in Minnesota, North Dakota, and South Dakota, and postulate the identity of the seedling leaf rust resistance genes in the cultivars. Twenty-six cultivars, near-isogenic lines of Thatcher wheat that differ for single leaf rust resistance genes, and three wheat cultivars with known leaf rust resistance genes, were tested with 11 different isolates of leaf rust collected from the United States and Canada. The leaf rust infection types produced on seedling plants of the cultivars in greenhouse tests were compared with the infection types produced by the same isolates on the Thatcher near-isogenic lines to postulate which seedling leaf rust resistance genes were present. Seedling leaf rust resistance genes Lr1, Lr2a, Lr10, Lr16, Lr21, and Lr24 were postulated to be present in spring wheat cultivars. Seedling genes Lr3, Lr14a, and Lr23 likely were present in some cultivars but could not be clearly identified in this study. Most of the cultivars had some level of adult plant leaf rust resistance, most likely due to Lr34. Cultivars that had seedling resistance genes Lr1, Lr2a, Lr10, or Lr16 had poor to intermediate levels of leaf rust resistance in field plots. Cultivars with combinations of seedling resistance genes Lr16 and Lr24 with additional adult plant resistance were highly resistant to leaf rust.
39
Enebak, S. A., e W. A. Carey. "Plant Growth-Promoting Rhizobacteria May Reduce Fusiform Rust Infection in Nursery-Grown Loblolly Pine Seedlings". Southern Journal of Applied Forestry 28, n. 4 (1 novembre 2004): 185–88. http://dx.doi.org/10.1093/sjaf/28.4.185.
Testo completoAbstract (sommario):
Abstract Fusiform rust caused by Cronartium quercuum f.sp. fusiforme (Hedg. & Hunt ex Cumm.) is the most damaging stem disease of Pinus spp. in the southern United States. Plant-growth-promoting rhizobacteria (PGPR) have induced systemic resistance in many host-pathogen systems. To determine whether rhizobacteria could induce systemic resistance to fusiform rust infection, loblolly pine (Pinus taeda L.) seedlings were evaluated for rust resistance following preemergence seed and post emergence foliar sprays with three bacterial strains. Treated seed was sown in one bare root nursery in Alabama and one in Georgia, and seedlings were examined for size differences and rust galls at the end of one season. Treatment with bacteria at the time of sowing did not affect rust galls or seedling growth at the Alabama nursery but reduced galls and increased seedling growth at the Georgia nursery. Bacterial treatment T4 resulted in significantly fewer galls and strains T4 and SE34 resulted in larger seedlings compared to nontreated controls. This is the first report of a reduction in fusiform rust by plant growth-promoting rhizobacteria and although nursery × treatment interactions exist, the current findings suggest that induced systemic resistance is possible. South. J. Appl. For. 28(4):185–188.
40
Sun, Guo Rong, Xue Li Wu, Gang Chen, Jian Bo Wang, Wen Zhong Cao, Qun Du e Biao Zhang. "The Function of Chloroplast GST of Puccinellia Tenuiflora Seedling Leaves in Resistance to Na2CO3 Stress". Advanced Materials Research 343-344 (settembre 2011): 712–20. http://dx.doi.org/10.4028/www.scientific.net/amr.343-344.712.
Testo completoAbstract (sommario):
In order to probe into orderliness changes of Glutathione S-Transferase (GST) of chloroplast ofPuccinellia tenuifloraseedlings under Na2CO3stress and its function in resistance to Na2CO3stress, relative electric conductance, GST activity and the O2-.produce rate of the chloroplast, and the osmotic potential of leaves, and the osmotic potential of culture solution ofP. tenuifloraseedlings under different Na2CO3stress were concerned. The result shows that in the Na2CO3stress range of 0～0.4%, along with the increase of its intensity under different Na2CO3stress intensity, GST activity of the chloroplast of seedling leaves ofP. tenuiflorais strengthened and GST activity is rapidly weakened with the increase of the intensity of Na2CO3stress more than 0.4%. The change of GST activity of the chloroplast along with the osmotic potential of culture solution and seedling leaves, relative electric conductance of the seedling leaves as well as the O2-.produce rate have the similar change tendency. There is significant nonlinear relationship among GST activity of chloroplast, osmotic potential of the seedling leaves and Na2CO3concentration ofculture solution, and among GST activity of chloroplast, O2-.produce rate and osmotic potential of seedling leaves, and among GST activity of chloroplast, osmotic potential of culture solution and that of seedling leaves, and among GST activity, the O2-.produce rate of chloroplast and relative electric conductance of the seedling leaves. These indicate that GST of chloroplast plays an important role in the process of seedlings ofP. tenuiflorain resistance to the low intensity of Na2CO3stress.
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Sun, Yujun, Yunhan He, Ali Raza Irfan, Xinmeng Liu, Qiaoqiao Yu, Qian Zhang e Deguang Yang. "Exogenous Brassinolide Enhances the Growth and Cold Resistance of Maize (Zea mays L.) Seedlings under Chilling Stress". Agronomy 10, n. 4 (1 aprile 2020): 488. http://dx.doi.org/10.3390/agronomy10040488.
Testo completoAbstract (sommario):
This paper aims to elucidate the effects of exogenous brassinolide (BL) on maize germination and seedling growth under chilling stress. The cold-resistant maize hybrid Tiannong 9 and the cold-sensitive hybrid Tianhe 1 were soaked at the germination stage (6 °C) and leaves were sprayed at seedling stage (4 °C), with BL at concentrations of 0, 0.01, 0.1, and 1 mg/L. The germination rate of the maize seeds and the changes in seedling biomass, antioxidant, photosynthetic, and plant endogenous hormone systems and chloroplast ultrastructures were determined. The results showed that the optimum concentration of BL to alleviate chilling stress in maize seedlings was 0.1 mg/L. This rate effectively increased the germination rate and plant biomass of maize and significantly increased the superoxide dismutase (SOD) peroxidase (POD) and catalase (CAT) activities, the net photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr), and seedling auxin (IAA), gibberellin (GA3) and trans zeatin nucleoside (t-ZR) contents under chilling stress. In addition, BL significantly reduced the malondialdehyde (MDA) content, abscisic acid (ABA) content, and intercellular carbon dioxide concentration (Ci). In the comparison of mesophyll cells, the chloroplast membrane of the treatment group was tightly attached to the stroma, and some of the plasma membranes were dissolved, but the overall structure of the chloroplast was relatively complete, and the osmiophilic granules were relatively few. The exogenous application of BL can effectively alleviate the damage caused by a low temperature in maize, maintain the normal characteristics of seedlings in chilling environments, and ensure the development and growth of plant tissue in the later stage.
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Jelev, Natalia. "The influence of heat shock on the rate of reserves allocated by wheat seeds for germination and growth". Bulletin of the Academy of Sciences of Moldova. Life Sciences, n. 1 (343) (gennaio 2022): 60–69. http://dx.doi.org/10.52388/1857-064x.2021.1.08.
Testo completoAbstract (sommario):
We studied the accumulation and consumption of biomass by five-day-old seedlings of various wheat varieties (Triticum aestivum L.) grown from control and exposed to heat shock (HS) seeds. The suppression shoot and roots growth intensified with the temperature, which caused HS. With increasing the temperature (+50°С, +51°С, +52°С și +53°С) of HS, the biomass of the endosperm of the seeds transferred to the seedling, and spent on respiration during seed germination, and seedling growth decreased. Moreover, the effect of HS was more pronounced on the biomass of endosperm substances transferred to the seedling. To increase the resolution of separating wheat varieties according to their resistance to HS, we applied the optimal value (+52°С) of the HS temperature (HSo). The rate of dry matter transferred from the endosperm to the shoot, roots, and spent on respiration, made it possible to rank various wheat varieties following their resistance to high temperatures. The higher the resistance of a wheat cultivar to high temperatures, the higher the proportion of endosperm substances consumed by exposed to HSo seeds for seedling growth and respiration. With increasing the wheat varieties to high temperatures, the rate of endosperm biomass transferred to the seedling also increased, at the same time that spent on respiration on the contrary, decreased. After exposure to HSo, the seeds of the resistant to high temperatures varieties also showed higher metabolic efficiency than those of less resistant varieties. All parameters characterizing the resistance of leaves and roots to HS suggested that the high-temperature resistance of roots is lower than that of leaves. The method for determining the resistance of wheat varieties to high temperatures, based on the ability of seeds exposed to HSo, to mobilize reserve substances for germination and growth is fast, characterized by increased resolution, and ensures the distribution of wheat varieties according to their resistance to high temperatures.
43
Nandhini, D. Udhaya, e E. Somasundaram. "Effects of rhizobial nod factors (Lipo chitooligosaccharide) on seedling growth of maize (Zea mays L.) under salt stress". Bangladesh Journal of Botany 47, n. 4 (31 dicembre 2018): 831–37. http://dx.doi.org/10.3329/bjb.v47i4.47359.
Testo completoAbstract (sommario):
Effects of nod factors (lipo chitooligosaccharide) on seedling growth of maize under salt stress have been studied. The study was framed with seed priming using lipo chitooligosaccharide (LCO) a nod factor @ 4 ml/kg of seeds and without priming on maize seedling growth which was exposed to different levels of salinity (0, 2, 4, 6, 8 and 10 dS/m). Salinity negatively influenced the seedling growth of maize. However nod factor treated maize seedlings had relatively higher germination percentage, root length, shoot length, reducing sugars and amylase activity. Correlation analysis revealed positive relationships between seedling growth parameters. Thus, seed priming with nod factor (4 ml/kg) improved the resistance to salinity at seedling stage. NaCl concentrations restricted amylase enzyme activity and reducing sugar content in the germinating seeds. Priming of nod factor/LCO mitigated the restricted effects of salinity on amylase activity and reducing sugars.
44
Powers, H. R., e J. F. Kraus. "A Comparison of Fusiform Rust-Resistant Loblolly Pine Seed Sources". Southern Journal of Applied Forestry 10, n. 4 (1 novembre 1986): 230–32. http://dx.doi.org/10.1093/sjaf/10.4.230.
Testo completoAbstract (sommario):
Abstract A greenhouse inoculation study compared resistance to fusiform rust (Cronartium quercuum (Berk.) Miyabe ex Shirai f. sp. fusiforme) of loblolly pine (Pinus taeda L.) seedlings derived from bulk seed produced in 4 rust-resistant seed orchards, 1 rust-resistant geographic seed source (Livingston Parish, LA), and a control treatment of improved loblolly from a first-generation production orchard. The rust-resistant orchards included 2 forest industry orchards developed from the most rust-resistant clones available within a tree improvement cooperative (1st generation), and both a clonal and a seedling seed orchard from the Georgia Forestry Commission-USDA Forest Service (GFC-USFS) program (2nd generation). The most resistant seedlings (61% rust free) were from the GFC-USFS seedling orchard. The Livingston Parish seedlings and those from the GFC-USFS clonal orchard had significant resistance, both groups being 44% rust free. One forest industry orchard was intermediate in resistance (34% rust free), whereas the second industry orchard was not significantly different from the controls, with 19 and 13% of the seedlings rust free, respectively. The results emphasize the value of increased selection pressure in the future production of highly rust-resistant seedlings with a broad genetic base, and demonstrates the gains that can be achieved in advanced generations. South. J. Appl. For. 10:230-232, Nov. 1986.
45
Boyden*, Laurie E., e Peter Cousins. "Segregation of Resistance to Root-knot Nematodes in a Vitis Nesbittiana Hybrid Population". HortScience 39, n. 4 (luglio 2004): 804C—804. http://dx.doi.org/10.21273/hortsci.39.4.804c.
Testo completoAbstract (sommario):
Development of rootstocks resistant to root-knot nematodes (Meloidogyne spp.) is a priority in grape breeding. The N allele, present in Harmony and Freedom rootstocks, confers resistance to N-avirulent strains of Meloidogyne. Extensive planting of rootstocks containing N has led to the development of N-virulent nematode strains, prompting a search for new resistance alleles. A seedling population derived from Vitis nesbittiana Comeaux was evaluated to investigate the genetic control of nematode resistance in this species. Hybridization with easily propagated rootstock selections will be required to utilize nematode resistance found in V. nesbittiana, a native of Mexico. The female parent of the population was 161-49C, a V. riparia × V. berlandieri hybrid rootstock. 161-49C does not contribute nematode resistance to its progeny. The male parent was V. nesbittiana DVIT 2236.12, an accession held in the U.S. National Plant Germplasm system. Nematode resistance of the 161-49C × V. nesbittiana DVIT 2236.12 population was assessed in greenhouse pot culture. Seedling roots were stained in an eosin-Y solution six weeks after inoculation with 1500 N-virulent M. arenaria juveniles. Resistance classes of seedlings were determined by assessing the degree of galling and number of egg masses per root system. Segregation in the seedling population was consistent with a 1:1 ratio of resistance to susceptibility, indicating that the V. nesbittiana accession is heterozygous for a dominant allele conferring resistance to N-virulent root-knot nematodes. The genetic relationship between this allele and the N allele has yet to be determined.
46
Torres, Antonio C., Russell T. Nagata, Robert J. Ferl, Thomas A. Bewick e Daniel J. Cantliffe. "In vitro Assay Selection of Glyphosate Resistance in Lettuce". Journal of the American Society for Horticultural Science 124, n. 1 (gennaio 1999): 86–89. http://dx.doi.org/10.21273/jashs.124.1.86.
Testo completoAbstract (sommario):
Glyphosate-resistant plants of `South Bay' lettuce (Lactuca sativa L.) were produced by using Agrobacterium tumefaciens containing a plasmid carrying glyphosate oxidase and EPSPS gene. An in vitro assay was performed to determine the sensitivity of `South Bay' leaf discs and seedling explants to varying glyphosate concentrations. The I50 for glyphosate leaf discs was 53.8 μm and for glyphosate seedlings 7.6 μm. There was a high correlation between the response of leaf discs and seedlings to glyphosate based on dry weight. These findings will allow identification of glyphosate-resistant transformants in an early stage of plant development, saving time and reducing the cost in generating an improved cultivar with the glyphosate resistance trait.
47
Harder, D. E., J. Chong, P. D. Brown e J. W. Martens. "Inheritance of resistance to Puccinia coronata avenae and P. graminis avenae in an accession of Avena sterilis from Spain". Genome 33, n. 2 (1 aprile 1990): 198–202. http://dx.doi.org/10.1139/g90-031.
Testo completoAbstract (sommario):
Accessions of wild Avena spp. obtained from the Iberian Peninsula were screened for resistance to oat crown and oat stem rust. Of a number of accessions which showed resistance, A. sterilis accession IB3056 was selected for further genetic analysis because it had combined resistance to both crown and stem rusts and as a hexaploid was readily hybridizable with A. sativa. IB3056 was crossed and backcrossed with the susceptible cultivar 'Makuru' and progeny were analyzed for segregation to a range of rust races. A single dominant gene conferred resistance to crown rust. The resistance was highly effective against all isolates of Puccinia coronata avenae tested. The crown rust resistance of IB3056 was due either to gene Pc68 or was very closely linked or allelic to Pc68. Seedling plants of the IB3056 parent were susceptible to all isolates of P. graminis avenae tested, but in the adult plant stage they were resistant. All IB3056/2* Makuru progeny also were susceptible to stem rust as seedlings, but BC1F2 adult plants segregated for resistance in ratios indicating a single dominant gene, designated Pg17.Key words: oat crown rust, oat stem rust, adult plant resistance, seedling resistance
48
Abbott, DC, JJ Burdon, AM Jarosz, AHD Brown, WJ Muller e BJ Read. "The relationship between seedling infection types and field reactions to leaf scald in Clipper barley backcross lines". Australian Journal of Agricultural Research 42, n. 5 (1991): 801. http://dx.doi.org/10.1071/ar9910801.
Testo completoAbstract (sommario):
Eighty-four third backcross (BC) lines of barley with different chromosomal segments of Hordeum spontaneum in a H. vulgare (cv. Clipper) background, were tested for resistance to a mixture of isolates of Rhynchosporium secalis using a seedling assay. Twelve of the lines were classed as resistant, including two which segregated for resistance. Plants tested using the seedling assay were subsequently planted in the field in Canberra and levels of disease monitored through to plant maturity. Seedling assay scores and field disease levels were closely correlated (r = 0.72, P < 0.001). Furthermore, grain yields for resistant BC-lines were 25% higher, on average, than those for susceptible lines. A separate field trial containing a selection of these lines was conducted in a scald-prone barley growing area (Wagga Wagga). The results obtained were consistent with those from the Canberra trial. The experiments demonstrate that resistances to leaf scald in H. spontaneum, first detected as seedling response types, also function to increase the resistance of barley throughout the growing season.
49
White, E. E., E. A. Allen, C. C. Ying e B. M. Foord. "Seedling inoculation distinguishes lodgepole pine families most and least susceptible to gall rust". Canadian Journal of Forest Research 30, n. 5 (1 maggio 2000): 841–43. http://dx.doi.org/10.1139/x00-013.
Testo completoAbstract (sommario):
Resistance of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) to western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka) was compared between 21-year field infection trials and inoculation of 2-month-old seedlings. The seedlings were produced from seed stored since the original field plantings. Virtually all of the seedlings from families identified as susceptible in the field produced galls in the inoculation trial, only 1% of seedlings from these families did not develop galls. Nearly half the seedlings in families classed as resistant in the field trials did not form galls 13 months after inoculation. Only one of these seedlings developed galls in the following 2 years. Seedling inoculation provides a simple early test to assess field resistance to gall rust of lodgepole pine seedlots, and an efficient way to cull at least the most susceptible ones.
50
Scott, J. H., R. L. Brandenburg, G. G. Kennedy e T. G. Isleib. "Laboratory Bioassay Evaluating Peanut Seedlings for Resistance to the Southern Corn Rootworm, Diabrotica undecimpunctata howardi Barber (Coleoptera: Chrysomelidae)". Peanut Science 30, n. 1 (1 gennaio 2003): 43–48. http://dx.doi.org/10.3146/pnut.30.1.0009.
Testo completoAbstract (sommario):
Abstract The objective of this study was to develop a laboratory bioassay that consistently distinguishes peanut genotypes (Arachis hypogaea L.) based on their potential susceptibility or resistance to the southern corn root-worm (SCR), Diabrotica undecimpunctata howardi Barber, a major soil insect pest of peanut in North Carolina, Virginia, and other states. The susceptibility or resistance of a peanut genotype to the SCR was characterized by the survival, development, and mean weight of the pest after feeding for 14 d on seedlings of different peanut genotypes. An initial 14 d seedling bioassay demonstrated the ability of the technique to separate a susceptible cultivar (NC 7) from a resistant cultivar (NC 6) based on the percentage of SCR that survived after 14 d, the percentages and mean weight of surviving SCR in larvae, prepupae, and pupae. Subsequently, two 14 d seedling bioassays evaluated five additional peanut genotypes that were believed to have some resistance to the SCR (N97059N, N92069L, VA 861101, VT 9506114–1, NC-GP WS 9) along with the susceptible (NC 7) and resistant (NC 6) controls. The final two bioassays were modified to test the differences in the percentages of SCR adults that emerged and the time required for adult emergence after feeding as larvae on the susceptible (NC 7) and resistant (NC 6) peanut seedlings. The 14 d seedling bioassay represents an improvement over earlier seedling bioassays because of its consistent ability to distinguish susceptible and resistant peanut genotypes, and because of the diversity of parameters measured. It consistently separated the susceptible (NC 7) and resistant (NC 6) controls, with one or more of the parameters measured. The breeding line N92069L and the germplasm line NC-GP WS 9 were shown to result in significantly lower survival of SCR and to delay development relative to the susceptible control NC 6. A seedling bioassay where eggs were allowed to develop to the adult stage repeatedly separated NC 7 from NC 6 based on the percentages of adults that emerged. Results indicate the seedling bioassay should be a reliable method for screening large numbers of peanut genotypes before committing the time, space, and labor required for field evaluations. In addition, future peanut breeding programs should consider attempting to introduce the resistance expressed in NC-GP WS 9, N92069L, and N97059N into lines with desirable agronomic characteristics.