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Published: 4 June 2021

Last updated: 30 July 2024

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1

Hurlburt, M. W. II, and D. T. Ray. "Thermodormancy in Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/214771.

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Most lettuce (Lactuca sativa L) seed fails to germinate at high temperatures. This phenomenon thermodormancy, is common in desert regions where 87% of all lettuce is grown in the U.S.A. A study was conducted using a non-thermodormant plant introduction, PI 251245, and two highly thermodormant Dutch butterhead cultivars, 'Dabora' and 'Severa'. Reciprocal crosses were made and germination trials conducted to observe how maternal and paternal influence and seed color contribute to thermodormancy. At 25 °C, germination was 100% for the three parents and the reciprocal F1 hybrids. Germination differences occurred at both 30° and 35 °C among the parents, with P1251245 with 100% germination and Dabora and Severa with less than 10% germination at both temperatures. Segregating F3 and F4 populations from Dabora x PI 251245 were investigated further. Genetic variation found between families suggests that breeding lettuce for improved thermotolerance may be possible. Seed color did not influence thermodormancy.

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2

Clark, L. J., R. Walser, and E. W. Carpenter. "Lettuce Variety Trial." College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/220344.

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Eleven head lettuce varieties and four leaf lettuce varieties were grown in a replicated small plot trial on the Safford Agricultural Center in 1998. Desertgreen variety of head lettuce from Harris Moran produced a crop with the best head weight, size and firmness rating. Premiere variety followed closely behind. Of the leaf lettuce varieties tested, Saguaro Romaine produced the best quality and quantity product. Per acre yields are calculated for each variety in the study.

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3

McGrady, John, Michael Matheron, John Palumbo, Michael Rethwisch, Marvin Butler, Joe Matejka, and Phil Tilt. "Sustainable Lettuce Production." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221435.

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4

Butler, Marvin, and Stan Heathman. "Poast/Lettuce Trial." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221442.

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5

Contreras, Samuel A. "Effects of maternal plant environment on lettuce (Lactuca sativa L.) seed dormancy, germinability, and storability." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196451272.

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6

Campbell, Paul. "Genetic modification of lettuce for resistance to lettuce necrotic yellows virus /." [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17584.pdf.

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7

Ray, Dennis T., James D. McCreight, John J. McGrady, and Judith K. Brown. "Resistance in Cultivated and Wild Lettuce to Lettuce Infectious Yellows Virus." College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/214277.

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In 1988, Arizona's early- season lettuce crop was plagued by disease and insect problems, both intensified by unseasonably high temperatures. In the western Arizona production area, an epidemic of lettuce infectious yellows (LIY) resulted in serious economic losses to growers. The yellows disease is incited by the LIY virus (LIYV), a plant virus transmitted by the sweet potato whitefly [Bemisia tabaci (Gene.)]. Disease symptoms in lettuce include stunted growth, rolling yellowing and /or reddening of infected leaves; necrotic lesions appear at or near the leaf margins at latter stages of the disease. LIYV has a wide host range which increases the difficulty of isolating lettuce fields from LIYV infected or whitefly-infested fields; also, whiteflies are resistant to insecticides. Therefore, host-plant resistance appears to be the most promising means of reducing losses due to this disease. To initiate a breeding program, commercial lettuce cultivars and breeding lines (Lactuca sativa L.), and related, cross-breeding wild lettuce species (L. serriola L. and L. saligna L.) were screened for resistance to LIYV in the western Arizona production area using natural inoculation by residence whiteflies.

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8

Palumbo, John C., and Todd A. Hannan. "Population Growth of Lettuce, Nasonovia ribisnigris, on Resistant Butter and Head Lettuce Cultivars." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/214949.

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Studies to examine lettuce aphid population growth on resistant head and butter lettuce cultivars were conducted in small filed plots at the Yuma Agricultural Center. By artificially infesting plants on several lettuce plantings during the spring, the influence of the resistant lettuce plants were evaluated for their capability of preventing lettuce aphid populations from colonizing plants. Results of five field trials showed that several varieties of head and butter lettuce have been developed that almost completely prevent lettuce aphids from surviving and reproducing on plants during the spring. Although the cultivars tested did not posses marketable characteristic for harvests, they do provide germplasm for breeding new varieties suited for desert production. In addition, these studies also support conclusions drawn from the past several seasons that suggest lettuce aphid population growth is greatest when ambient temperatures average between 65-70 °F.

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9

Wilcox, Mark. "Cultural Practices in the Production of Iceberg Lettuce in Southwestern Arizona." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 1994. http://hdl.handle.net/10150/147027.

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10

Palumbo, John C., F. J. Reyes, C. H. Jr Mullis, A. Amaya, L. Ledesma, and L. Carey. "Neonicotinoids and Azadirachtin in Lettuce: Comparison of Application Methods for Control of Lettuce Aphids." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/214930.

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Several small-plot field studies were conducted at the University of Arizona, Yuma Agricultural Center in the spring 2001 growing season to evaluate various neonicotinoids and azadirachtin products against lettuce aphid, Nasonovia ribisnigri, in lettuce. Further, these products were compared as soil-applied treatments, foliar sprays and application through sub-surface irrigation. The results of these trials provide useful information for understanding how to effectively use the new chemistries available for aphid management in lettuce. First, Platinum performed best as a post-planting application through a side-dress application or through the drip. The foliar neonicotinoids, Assail and Actara were active against lettuce aphids, but were most effective when populations densities were lower. Comparatively, the conventional chemistries (MSR, Orthene/Provado, Provado/Endosulfan) provided consistent control when used aggressively. The azadirachtin products were significantly less effective against LA in head lettuce due largely to their inability to contact the insects, but on formulation (AzaDirect) showed better efficacy when applied through drip irrigation or sprayed repeatedly in romaine lettuce.

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11

McHale, T. "Sclerotinia disease of lettuce crops." Thesis, Liverpool John Moores University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380665.

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12

Oebker, Norm, Ed Ryder, Fred Harper, and Marcia White. "Lettuce Tipburn Studies in Arizona." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/214492.

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13

Tickes, B. "Timing Kerb Applications in Lettuce." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/214938.

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Kerb (Pronamide) is often ineffective when it is leached below germinating weed seeds with sprinkler irrigation. Efficacy can be improved by making delayed aerial applications after the sprinklers have been started and before weeds have become established. Tests were conducted to determine the optimal time of application. Optimal times varied with the season and ranged from two to three days after the sprinklers had started during the early season (Sept.) to five to six days during the late season (January).

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14

Umeda, Kai. "Beet Armyworm Control in Lettuce." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/214940.

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Success®, Proclaim®, and Confirm® treated lettuce exhibited no beet armyworm (BAW) larvae at 3 days after treatment (DAT). Avaunt®, Intrepid®, and S-1812 (Valent) treated lettuce had no medium-sized larvae but 0.3 to 0.5 small larvae were observed. At 7 and 10 DAT, BAW populations diminished significantly in all of the lettuce and no larvae or eggs were observed in any lettuce.

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15

Maboko, Martin Makgose. "Growth, yield and quality of tomatoes (Lycopersicon esculentum Mill.) and lettuce (Lactuva sativa L.) as affected by gel-polymer soil amendment and irrigation management." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-02202007-105100.

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16

Matheron, Michael E., and Martin Porchas. "Reaction of Different Cultivars of Lettuce to Development of Powdery Mildew on Lettuce in 2001." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/214920.

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Seven different cultivars of lettuce were seeded and watered on Dec 1, 2000 at the Yuma Valley Agricultural Center. Cultivars were rated for severity of powdery mildew caused by Erysiphe cichoracearum at plant maturity (Mar 21). The highest levels of powdery mildew were found on the cultivars Winterhaven and Silverado, whereas lower disease severity was observed on Jackel, Cibola, RC-74 and Accolade. All tested cultivars would have required application of fungicides to reduce the amount of powdery mildew to acceptable levels. On the other hand, planting of lettuce cultivars with some disease tolerance may require less fungicide inputs to achieve acceptable disease control compared to planting susceptible cultivars.

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17

Palumbo, John C. "Seasonal Abundance and Control of the Lettuce Aphid, Nasonovia ribisnigri, on Head Lettuce in Arizona." College of Agriculture, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/220018.

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Small plot studies were conducted in 1999/2000 to examine the population abundance and control of the lettuce aphid on winter and spring head lettuce crops. Seven, 0.25 acre planting of head lettuce were established beginning in October with final harvest occurring in April. Replicated plots within several planting were treated with an Admire treatment at planting, a sidedress application of Platinum post-planting or allowed to remained untreated. Lettuce aphids were first detected in our experimental area on Feb 14 in PD 3 in untreated plants. Temperature had an important influence upon lettuce aphid development based on our field observations. Population appeared to increase in early March when the average daily temperature was about 65 °F. We observed a sharp decline in population abundance in April where daytime highs exceeded 90 °F. We were surprised by the marginal level of lettuce aphid control provided by the systemic insecticides. Lettuce treated with Admire in the early planting dates appeared to prevent lettuce aphids from significantly infesting lettuce heads at harvest. In the later planting dates, both Admire and Platinum contained significantly fewer aphids and infested plants than the untreated control. However, lettuce aphids in the last 3 planting dates were able to colonize plants and infest a larger proportion of heads at levels not considered commercially acceptable. We are hesitant to draw conclusions from our results collected from a single season , and plan to replicate this work next year under different environmental conditions and higher rates of Admire and Platinum.

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18

Palumbo, John C. "Influence of Planting Date and Insecticidal Control on Seasonal Abundance of Lettuce Aphids on Head Lettuce." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/214927.

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Small plot studies were conducted from 1999-2001 to examine the population abundance and control of the lettuce aphid on winter and spring head lettuce crops. In each year, Seven, 0.25 acre planting of head lettuce were established beginning in Sep-Oct with final harvest occurring in April. Replicated plots within several planting were treated with an Admire treatment at planting, a side dress application of Platinum post-planting or allowed to remain untreated. Lettuce aphids were first detected in our experimental area in December in PD 3 in 2001, but in 2002 first occurred in lettuce almost 2 months later (Feb 21). Similarly, lettuce aphid abundance was much greater in 2001 than in 2002, probably a result of temperature difference. Temperature had an important influence upon lettuce aphid development based on our field observations. Population appeared to increase in early March when the average daily temperature was about 65 E F. We observed a sharp decline in population abundance in April where daytime highs exceeded 90E F. Insecticide treatments also influenced seasonal abundance. Under heavy aphid pressure in 2001, lettuce treated with Admire in the early planting dates appeared to prevent lettuce aphids from significantly infesting lettuce heads at harvest. However, lettuce aphids in the last 3 planting dates were able to colonize plants and infest a larger proportion of heads at levels not considered commercially acceptable. Under lighter pressure in 2002, lettuce aphids did not significantly colonize Admire treated lettuce. Green peach aphid, potato aphid and foxglove aphids were also present in both years, but seldom reached economic levels, and where completely controlled in plots treated with soil, systemic insecticides.

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19

Matheron, M., J. McGrady, M. Butler, M. Rethwisch, J. Matejka, and P. Tilt. "Effect of Sunstainable Versus Conventional Fertilization Practices on Populations of Pythium and Fusarium on Roots of Lettuce in 1990 Field Test." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221453.

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This report focuses upon our efforts to evaluate the effect of sustainable versus conventional fertilization practices on subsequent populations of soil-borne pathogens on lettuce roots. The different fertilization treatments included conventional fertilizer, composted cow manure, and a biological soil conditioner. Near plant maturity, lettuce roots were collected from the field and the populations of Pythium and Fusarium were determined. The lowest population of both of these pathogens was found in the plots fertilized with composted cow manure, while the highest levels of Pythium and Fusarium were detected in the plots treated with conventional fertilizer. Further field studies are planned to confirm these initial findings. Of the two pathogens assayed, Pythium is of greatest concern because of its ability to destroy roots and reduce plant growth and vigor. Species of Fusarium are commonly found in soil and on plant roots and usually do not cause damage to plants unless the plants are under stress.

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20

Wilcox, Mark. "Crisphead Lettuce Variety Trials 1995/96." College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/214725.

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21

Butler, Marvin. "Kerb/Lettuce Variety Trial, 1989/1990." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221458.

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22

Wilcox, Mark. "Crisphead Lettuce Variety Trials 1994/1995." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/221460.

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23

Podetta, N. "NITRATE METABOLISM IN LETTUCE AND ROCKET." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/230014.

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Abstract Intensive farming techniques with highly fertilization management lead to produce leafy vegetables with high accumulation of nitrates. The Reg. UE 1258/2011 imposes threshold on nitrate content beyond which the vegetables (lettuce, rocket and spinach) cannot be placed on the market. It is so important to adopt strategies which reduce nitrate levels in leaves. This objective can be achieved through the studies on the metabolism of nitrates in model and greatest commercial interest species. This study focuses on cultivation in floating system because was shown that this cultivation technique has the ability to reduce the intake of macronutrients in the nutrient solution, making more efficient the assimilation of nitrogen by the plants and so reducing the level of nitrates in vegetables (Rouphael et al., 2004). Two leafy vegetables were chosen as study-species, lettuce (Lactuca sativa L.) and rocket (Diplotaxis tenuifolia L.) that have different efficiency of use and organication of nitrates. Some researchers have found levels of nitrate in Diplotaxis higher than 9300 mg*kg-1 FW (Santamaria et al., 1999; Cerutti et al., 1996), in fact rocket it is considerate a hyper accumulator of nitrates. This research focuses on comparative biology studies between the two species and on their nitrate metabolism to understand which are the factors that make the difference in the nitrate accumulation. Nitrate reductase, NR, (E.C.1.7.1.1-3) is the first enzyme from which start NO3- organication. Concentration in nitrates in the nutrient solution and other abiotic factors like light intensity and exposure, diurnal alternation of light and dark, temperature, CO2 levels, hormones (cytokinin, ethylene) (Dordas, 2009), anoxia, availability of sugars and nitrogen metabolites such as glutamine all play regulatory roles in NR activity (Crawford, 1995). The growing experiments performed for this thesis were planned to characterize the nitrate metabolism in lettuce and rocket plants grown in nutrient solutions containing different nitrate concentrations and under different light exposure. To achieve this objective the plants were cultivated, on the one hand, in conditions very similar to reals one, in greenhouse and with nutrient solution containing 2, 10 and 20 mM NO3-, but also with nutrient solution with low nitrate concentrations, 0.25, 0.5, 1 and 2 mM NO3-, gave after 1 day of nitrogen starvation, to highlight the high sensitiveness of nitrate transporters, and consequently on nitrate reductase, at small differences of nitrate in the nutrient solution. On the other hand the cultivations were carried out in a growth chamber in order to eliminate the influence on the results of some environmental parameters, which are difficult to evaluate in an uncontrolled environment and the aforesaid low nitrate concentrations were tested. The qualitative parameters, as content of chlorophylls, carotenoids, nitrates, nitrites, sucrose, reducing and total sugars were determinate to understand the status of the plants sampled at different environmental conditions and to evaluate how the different concentration of nitrates in the nutrient solutions affect these parameters. Then the activity of NR was measured using two different assays to understand the response of this enzyme at the different conditions used and to be correlated with the qualitative parameters, in order to deepen the mechanisms that affect the first step of reduction of the nitrates and, consequently, their organication to glutamate and amino acids. The study was integrated with the gene expression analysis for the main enzymes involved in the nitrate metabolism of lettuce and rocket: nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase and nitrate transporter (NTR). These analysis were performed using quantitative retro-transcriptase PCR (qRT-PCR) to study the transcriptional regulation under the different nitrate concentrations availability.

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24

Suzuki, Gerson Shinya [UNESP]. "Comportamento de genótipos de alface com o alelo mo10 ao Lettuce mosaic virus e Lettuce mottle virus." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/113793.

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Made available in DSpace on 2015-01-26T13:21:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-08-19Bitstream added on 2015-01-26T13:30:58Z : No. of bitstreams: 1 000806750.pdf: 405498 bytes, checksum: d7b936b62c9737ef848ca34aff10a7e8 (MD5)
A alface (Lactuca sativa L.), pertencente à família Asteraceae, é uma das hortaliças mais consumidas no Brasil. Um dos principais problemas fitossanitários para essa cultura são as fitoviroses, em especial o Lettuce mosaic virus (LMV), que causa elevados prejuízos aos produtores em diversas regiões do país, além do Lettuce mottle virus (LeMoV), que vem crescendo em importância nos últimos anos. Como forma de controle, o uso de variedades resistentes é maneira mais eficaz de contornar os danos causados por vírus. Na maioria das variedades resistentes de alface faz-se o uso de genes recessivos, em sua maioria envolvidos na interação planta-vírus, são os chamados codificadores de fatores de iniciação de tradução eucarióticos (eIFs). Diante disso, este trabalho teve como objetivo avaliar dois genótipos de alface (169501 e 169501C), quanto a resistência ao LMV e ao LeMoV. Foram realizadas transmissões via extrato vegetal nos dois genótipos de alface com LMV e LeMoV em diferentes intervalos de tempo. Para LMV também foram realizadas transmissões por afídeos. As duas variedades testadas se mostraram resistentes ao LMV nas duas formas de transmissão, mas apresentaram sintomas quando inoculadas com LeMoV. Em reações de RT-PCR com oligonucleotídeos específicos, foram comprovadas a ausência de LMV e a infecção por LeMoV nas plantas inoculadas. O isolado de LMV após análise do sequenciamento da porção N’ terminal da ...
Lettuce (Lactuca sativa L.) belongs to the Asteraceae family and is one of the most consumed vegetables in Brazil. One of the major disease problems in this crop are plant viruses, especially the Lettuce mosaic virus (LMV) that cause losses to producers in various regions of the country, but also Lettuce mottle virus (LeMoV). As a form of control, the use of resistant varieties is the most effective way to overcome the damage caused by plant viruses. Most of the resistant varieties of lettuce makes the use of recessive genes, mostly involved in plant-virus interactions and characterized as eukaryotic translation initiation factor (eIFs). Thus, this study aimed to evaluate two lettuce genotypes (169501 and 169501C) for resistance to LMV and LeMoV. LMV and LeMoV were sap transmitted at different time of intervals. For LMV also transmissions with aphids were carried out. The two varieties tested were resistant to LMV in both forms of transmission, but showed symptoms when inoculated with LeMoV. In RT-PCR with specific primers, LMV was not detected but LeMoV yes, confirming the infection in the inoculated plants. The isolate of LMV used in the tests was not classified as belonging to subgroups Most ...

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25

Suzuki, Gerson Shinya 1984. "Comportamento de genótipos de alface com o alelo mo10 ao Lettuce mosaic virus e Lettuce mottle virus /." Botucatu, 2014. http://hdl.handle.net/11449/113793.

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Orientador: Renate Krause Sakate
Banca: Marcelo Agenor Pavan
Banca: Massaharu Marubayashi
Resumo: A alface (Lactuca sativa L.), pertencente à família Asteraceae, é uma das hortaliças mais consumidas no Brasil. Um dos principais problemas fitossanitários para essa cultura são as fitoviroses, em especial o Lettuce mosaic virus (LMV), que causa elevados prejuízos aos produtores em diversas regiões do país, além do Lettuce mottle virus (LeMoV), que vem crescendo em importância nos últimos anos. Como forma de controle, o uso de variedades resistentes é maneira mais eficaz de contornar os danos causados por vírus. Na maioria das variedades resistentes de alface faz-se o uso de genes recessivos, em sua maioria envolvidos na interação planta-vírus, são os chamados codificadores de fatores de iniciação de tradução eucarióticos (eIFs). Diante disso, este trabalho teve como objetivo avaliar dois genótipos de alface (169501 e 169501C), quanto a resistência ao LMV e ao LeMoV. Foram realizadas transmissões via extrato vegetal nos dois genótipos de alface com LMV e LeMoV em diferentes intervalos de tempo. Para LMV também foram realizadas transmissões por afídeos. As duas variedades testadas se mostraram resistentes ao LMV nas duas formas de transmissão, mas apresentaram sintomas quando inoculadas com LeMoV. Em reações de RT-PCR com oligonucleotídeos específicos, foram comprovadas a ausência de LMV e a infecção por LeMoV nas plantas inoculadas. O isolado de LMV após análise do sequenciamento da porção N' terminal da ...
Abstract: Lettuce (Lactuca sativa L.) belongs to the Asteraceae family and is one of the most consumed vegetables in Brazil. One of the major disease problems in this crop are plant viruses, especially the Lettuce mosaic virus (LMV) that cause losses to producers in various regions of the country, but also Lettuce mottle virus (LeMoV). As a form of control, the use of resistant varieties is the most effective way to overcome the damage caused by plant viruses. Most of the resistant varieties of lettuce makes the use of recessive genes, mostly involved in plant-virus interactions and characterized as eukaryotic translation initiation factor (eIFs). Thus, this study aimed to evaluate two lettuce genotypes (169501 and 169501C) for resistance to LMV and LeMoV. LMV and LeMoV were sap transmitted at different time of intervals. For LMV also transmissions with aphids were carried out. The two varieties tested were resistant to LMV in both forms of transmission, but showed symptoms when inoculated with LeMoV. In RT-PCR with specific primers, LMV was not detected but LeMoV yes, confirming the infection in the inoculated plants. The isolate of LMV used in the tests was not classified as belonging to subgroups Most ...
Mestre

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26

Callaghan, Ben. "Sequence analysis and variability study of Lettuce necrotic yellows virus /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18662.pdf.

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27

Bestwick, Charles Stuart. "Characterization of the hypersensitive reaction in lettuce." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309117.

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28

Fan, Shimin. "Factors affecting health-beneficial compounds in lettuce." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121493.

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Lettuce contains several health-beneficial compounds. Increasing the concentration of key health-beneficial compounds in lettuce has thus become an objective of several breeding programs and producers. In a first experiment, 38 genotypes of lettuces including crisphead, butterhead, romain, leaf lettuce, stem, Latin and wild species, were grown in greenhouses at two sites and concentrations of major flavonoids and phenolic compounds were quantified. In a second experiment, 6 cultivars of lettuce were grown in growth chambers with high (20°C night/28°C day) or control (14°C night/18°C day) temperatures to study the effect of heat stress on the concentration of health-beneficial compounds in lettuce. The results indicated that concentrations of total flavonoids, total phenolics, Ferric-Reducing Antioxidant Power (FRAP) and chicoric differed significantly among lettuce genotypes. Results at the two sites were highly correlated, thus selection at one site may be sufficient. Among the most commonly cultivated types, red leaf lettuces had the highest total flavonoids concentration at the maturity stage, followed by butterhead, and green leaf, while crisphead and batavia had the lowest concentrations. Health-beneficial compounds could be affected by heat stress in lettuce, however, different lettuce cultivars responded differently to the heat stress.
La laitue contient plusieurs composés bénéfiques pour la santé. L'augmentation de la concentration des principaux composés bénéfiques pour la santé dans la laitue est ainsi devenue un objectif de plusieurs programmes d'amélioration et de producteurs. Dans une première expérience, 38 génotypes de laitues dont pommée, butterhead, Romain, laitue en feuilles, les espèces latine et sauvages, ont été cultivés dans des serres à deux sites et les concentrations des principaux flavonoïdes et des composés phénoliques ont été quantifiés. Dans une seconde experience, 6 cultivars de laitue ont été cultivés dans des chambres de croissance avec températures élevées (20°C nuit/28°C jour) ou un témoin (14°C nuit/18°C jour) pour étudier l'effet du stress thermique sur la concentration de composés bénéfiques pour la santé dans la laitue. Les résultats indiquent que les concentrations de flavonoïdes totaux, composés phénoliques, le pouvoir de reduction antioxydant de l'ion ferrique (FRAP), l'acide chlorogénique et l'acide chicorique différent significativement entre les génotypes de laitue. Les résultats aux deux sites étaient fortement corrélés, et une sélection à un site pourrait suffire. Parmi les types, les plus couramment cultivées, les laitues à feuilles rouges avaient la plus forte concentration totale en flavonoïdes, suivie par les types semi-pommés (butterhead), et ceux à feuilles vertes, tandis que la laitue pommée et batavia avaient les concentrations les plus faibles. Les composésixbénéfiques pour la santé dans la laitue étaient affectés par un stress thermique cependant la réponse dépendait des cultivars.

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29

Zhang, Jianhua. "Diversity of aster yellows phytoplasmas in lettuce." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1054584888.

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30

Zhang, Jianhua. "Diversity of aster yellows phytoplasmas in lettuce." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1054584888.

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31

Kerns, David L. "Common Insect Contaminants Found in Arizona Lettuce." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2000. http://hdl.handle.net/10150/144795.

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2 pp.
This publication describes the common insects found in Arizona lettuce through the use of pictures. The insects include; lepidopterous larva, striped flea beetle, leafminer fly, leafminer mine, adult western flower thrips, winged adult aphid, false chinch bug, lygus bug, potato leafhopper, and threecornered alfalfa hopper.

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32

Tickes, Barry R. "Lettuce Injury from Preplant and Preemergence Herbicides." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/146740.

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33

Martin, Edward, Donald Slack, and E. James Pegelow. "Water Use in Vegetables - Western Head Lettuce." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2009. http://hdl.handle.net/10150/146966.

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2 pp.
More lettuce is grown in Arizona than any other vegetable crop. Water stress in head lettuce can cause poor yields (tonnage) or poor quality (firmness, head size, color). This publication addresses how to water head lettuce growing in Arizona and how to manage commercial irrigation.

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34

Rethwisch, Michael D. "Control of Liriomyza trifolii in Head Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/214482.

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35

Rethwisch, Michael D., Michael Meadows, Shari Hagerman, James Thiessen, and John McGrady. "Effects of Lettuce Insecticides Applied at Planting." College of Agriculture, University of Arizona (Tucson, AZ), 1992. http://hdl.handle.net/10150/214518.

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36

Umeda, Kai. "Screening Herbicides for Lettuce, Broccoli, and Spinach." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2003. http://hdl.handle.net/10150/214991.

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Nicosulfuron, quinclorac, triflusulfuron, MKH-3586, pyraflufen, and tribenuron applied PREE appeared to be safe on the lettuce crops while demonstrating variable activity against weeds. Head lettuce and romaine were not as tolerant to POST herbicides compared to PREE herbicides. Sulfosulfuron, MKH-3586, rimsulfuron, ethametsulfuron and pyraflufen applied POST caused various degrees of injury on the lettuces that were less injurious than other treatments. Thifensulfuron, nicosulfuron, and quinclorac applied PREE or POST showed acceptable broccoli tolerance. Ethametsulfuron exhibited adequate safety when applied POST on broccoli. Thifensulfuron, nicosulfuron, and quinclorac applied PREE also showed spinach tolerance. Similar to head lettuce and romaine spinach was not as tolerant to POST herbicides compared to PREE herbicides.

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37

Chen, X. "TAGGING BIOCONTROL STREPTOMYCES TO STUDY LETTUCE COLONIZATION." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/345187.

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The ability of the biological control agents (BCAs) to colonize plant tissues is an important feature involved in microbe-assisted plant protection. Plant-microbe interaction research increased especially in the last decade thanks to technological revolution. Molecular methods and the development of advanced microscopic techniques allow researchers to explore gene expression and localization of beneficial microorganisms within plants. The green fluorescent protein (GFP) and its modified version, enhanced GFP (EGFP), more adapt for expression in mammalian cells and GC-rich actinomycetes like Streptomyces, have been widely used as markers to study gene expression, as well as plant-microbe interactions. Aside fluorescent protein approaches, fluorescence in situ hybridization (FISH) is another frequently used technique to visualize microbial colonization patterns and community composition by application of specific fluorescent probes. Firstly, we transformed five Streptomyces strains, which showed strong inhibition activity against Sclerotinia sclerotiorum, with the EGFP construct by the conjugation method. The conjugation efficiencies varied between the strains, but were comparable to the reference strain. The fitness of transformed strains was similar to wild-type; the transformants maintained similar sporulation, mycelium growth rate, and the ability to produce important secondary metabolites and lytic enzymes. Secondly, two transformed strains, Streptomyces cyaneus ZEA17I, and Streptomyces sp. SW06W, were used to study lettuce colonization dynamics by seed coating method. Their spatio-temporal dynamics were determined in sterile substrate. The strains were consistently recovered from lettuce rhizosphere and inner root tissues up to six weeks. Finally, the colonization pattern of lettuce by Streptomyces cyaneus ZEA17I was examined by both EGFP and FISH approaches combined with confocal laser scanning microscopy (CLSM). For FISH-CLSM analysis, universal bacteria and Streptomyces genus specific probes were used to label S. cyaneus ZEA17I. The consistent presence of the labeled strain at the lettuce root one week after sowing showed that Streptomyces spores could rapidly germinate and produce filamentous mycelium on lettuce. S. cyaneus ZEA17I was detected also on two-week-old roots, indicating the long-term survival ability of this strain in lettuce rhizosphere. Altogether, the antagonistic activity, rhizosphere and root competence showed by the Streptomyces conferred their potential to act as BCA. Further studies on the complex host-pathogen-antagonist interactions will provide additional knowledge to understand the modes and mechanisms of Streptomyces-mediated plant protection.

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38

Boshoff, Jane. "Biological control of Pythium wilt and root rot in hydroponically grown lettuce." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-02272007-163651/.

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39

Nelson, Merritt, Larry J. Stowell, and Tom Orum. "Slowing Spread of Lettuce Infectious Yellows Virus with Stylet Oil." College of Agriculture, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/214495.

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Infection by lettuce infectious yellows vines was reduced in lettuce treated with stylet oil. There was a difference in the final infection level between treated and untreated blocks and reduced infection in early readings. Yields were slightly better in the treated blocks. It has not been determined if and under what conditions it would be feasible to use this treatment on a practical scale.

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40

Wilcox, M., and C. A. Sanchez. "Evaluation of Foliar Applied Nutritional Mixes on Crisphead Lettuce for Yield, Quality and Incidence of Tipburn." College of Agriculture, University of Arizona (Tucson, AZ), 1994. http://hdl.handle.net/10150/214714.

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41

Oebker, N. F., and Mark Wilcox. "Effect of Agronomix on Crisphead Lettuce at Yuma - 1992." College of Agriculture, University of Arizona (Tucson, AZ), 1994. http://hdl.handle.net/10150/214715.

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42

Pritchard, Kevin H., Thomas A. Doerge, and Ted W. McCreary. "The Response of Leaf Lettuce to Phosphorous Fertilizer Placement and Rate." College of Agriculture, University of Arizona (Tucson, AZ), 1994. http://hdl.handle.net/10150/214729.

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A one-year field study was conducted at the Maricopa Agricultural Center in the winter and spring of 1991-92 with the purpose of comparing the response of leaf lettuce grown with subsurface drip irrigation to various broadcast and banded phosphorus (P) fertilizer applications and rates. Two rates of banded treble superphosphate, 250 lbs. (1X) and 125 lbs. (1/2X) of P2Osper acre, were applied immediately before planting in a concentrated strip 1 inch directly below the row to be seeded. One broadcast rate, 250 lbs. (1X) of P205 per acre of the same material, was applied and folded into the planting beds during listing. Control plots, in which zero P fertilizer was applied, were also maintained. Whole plant total P concentrations were higher in the first one-third of the growing season for the band treatments, though the differences in responses between band and broadcast applications were not statistically significant in the final third of the season. The 1X band treatment exhibited both greater plant heights and diameters than all other treatments during the first one-half of the growing season, and maintained greater height dimensions in the second half. The 1X broadcast and 1/2X band treatments exhibited similar growth throughout the season. By harvest there were not significant differences in head or plant size or in marketable yield among the three P treatments.

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43

Matheron, M. E., and J. C. Matejka. "Sclerotinia Leaf Drop of Lettuce - Screening New Fungicides for Disease Control in 1986." College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/221404.

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In western Arizona, the incidence and severity of lettuce drop, caused by the fungus Sclerotinia sclerotiorum, can be significant during February, March and April. During 1986 a field trial was established to test new fungicides for disease control. Disease severity in the inoculated lettuce planting was significantly reduced by Baycor, Spotless and CGA-449, as well as the registered fungicides Ronilan and Rovral. Further testing of Baycor, Spotless and CQA-449 will be performed next year.

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44

Al-Akel, Saleh, and Paul G. Bartels. "Water Stress-Induced Osmotic Adjustment in Expanding Leaves of Tepary Bean )Phaseolus actifolins, Gray) Seedlings." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221443.

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Tepary beans perform better than common beans under drought conditions. The mechanism of drought tolerance in tepary bean seedlings was explored by determining the water potential, osmotic potentia4 relative water content and level of free sugars and concentration of K ions within expanding leaves. Two week old seedlings were subjected to a gradual water stress with sorbitol solutions exhibiting OP values of -0.19 MPa and -0.47 MPa. Tugor remained constant whereas WP, OP and RWC declined following the stress treatment. Osmotic adjustment (0.4) occurred in each treatment but the contribution of sucrose and fructose to OA was minor. Some sorbitol was translocated to leaves and contributed to OA. The K ions did not contribute to the OA. A significant decrease in cell size was observed

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45

McGrady, John, Vince Rubatzky, Norm Oebker, Tim Hartz, Marvin Butler, Phil Tilt, and Sherry Hagerman. "Cultural Alternative for Avoidance of Lettuce Infectious Yellows Virus (LIYV)." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221452.

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46

Matheron, M. E., and J. C. Matejka. "Effect of Fungicides Applied at Different Rates on Control of Sclerotinia Leaf Drop of Lettuce -- 1990 Field Test." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221455.

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Leaf drop of lettuce, caused by the plant pathogenic fungi Sclerotinia sclerotiorum and S. minor, is found every year in some lettuce fields in Arizona. When environmental conditions are favorable, disease incidence and resulting crop loss can be significant. During the 1989 -90 lettuce season in western Arizona, different fungicides and rates of materials were evaluated in the field for disease control Ronilan and Rovral, the two fungicides currently registered for use on lettuce for control of Sclerotinia leaf drop, provided significant disease suppression and increased yields at all rates tested. Bravo and Botran did not control the disease.

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47

Palumbo, John C., Marvin D. Butler, and Clayton H. Jr Mullis. "Evaluation of Biological Insecticides for Control of Beet Armyworm in Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/221457.

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A field study was conducted at Yuma in 1990 to examine the efficacy of several biological insecticide formulations on beet armyworm in seedling lettuce. After a single application at thinning, none of the insecticides adequately reduced larval populations below damaging levels. Reductions in plant stand by larvalfeeding were significantly lower in plots treated with Lannate, Javelin, Biobit and Dipel. Lettuce seedling densities were reduced greaterthan 80% in untreated plots.

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48

Matheron, Michael E., and Martin Porchas. "Field Evaluation of Potential New Fungicides for Control of Lettuce Downey and Powdery Mildew in 1994 and 1995." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/221462.

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Downy and powdery mildew are caused by the plant pathogenic fungi Bremia lactucae and Erysiphe cichoracearum, respectively. Cool and moist environmental conditions favor development of downy mildew, while warmer and dry weather is conducive for development of powdery mildew. Potential new fungicides were evaluated for control of these diseases during 1994 and 1995. In 1994, downy mildew did not occur in the test plots; however, powdery mildew was severe and was controlled most effectively by Microthiol. In the 1995 study, both downy and powdery mildew developed in the test plots. The highest level of downy mildew control was achieved with three experimental compounds, Fluazinam, Dimethomorph, and BAS-490. The most effective fungicides for control of powdery mildew in 1995 were BAS-490 and Microthiol.

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49

Kerns, David L., and John C. Palumbo. "Efficacy of Insecticides to Green Peach Aphid on Iceberg Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/221464.

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Three tests were conducted evaluating foliar and soil applied aphicides for efficacy to green peach aphid infesting iceberg lettuce. Aphid population densites were low in all three studies and differences among treatments were difficult to discern. At low aphid populations we could not detect whether or not soil applications of Admire enhanced or inhibited the activity of subsequent foliar applications of other aphicides. Although when used alone, some products did offer statistically significant aphid control. However, in a commercial setting these differences would probably not be significant. At low aphid populations none of the pyrethroid tank mixes evaluated gave significantly better aphid control than the products used alone. All of the experimental aphicides evaluated appeared to have some degree of efficacy to green peach aphid.

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50

Kerns, David L. "Efficacy of Biorational Insecticides to Beet Armyworm and Cabbage Looper on Iceberg Lettuce." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/221466.

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Four tests were conducted evaluating biorational insecticides for control of beet armyworm (BAW) and cabbage looper (CL) on iceberg lettuce. Treatment means for BAW were difficult to separate due to low population densities. The new formulation of Javelin appeared to be the most efficacious Bt overall. However, when Bts were compared on a equal cost/A basis, there were no significant derences among products for CL control. All Bts were comparable to Lannate for CL control. The neem oil extract Align, provided adequate BAW and CL control, and its efficacy at low rates seemed to be slightly enhanced by the addition of Sunspray Ultrafine Oil. Larvin at lower than label recommended rates gave good BAW and CL control as did Javelin. The tank-mix of these two products did not enhance worm control over that of the products used alone. Mustang gave good control of CL but appeared to be slightly weak against BAW.

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