Littérature scientifique sur le sujet « Early watergra »

Molecular techniques are useful tools for solving taxonomic confusion among species. Polymerase chain reaction (PCR) and polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) methods were applied for the identification of barnyardgrass, early watergrass, and late watergrass. Total DNA was extracted from 266 accessions, which were collected from different rice growing areas of Turkey. The two primer sets (trn-a and trn-b1, and trn-c and trn-d) specific to a target region of the intergenic spacer between trnT (UGU) and trnL (UAA) and the entire intron region of trnL (UAA), respectively, were used in PCR amplifications. Of the 266 accessions of Echinochloa spp., only eight accessions gave a similar fragment size, which was slightly shorter than 495 bp. The PCR product obtained with the primers trn-a and trn-b1 gave two fragments when EcoRI restriction enzyme was used in barnyardgrass and early watergrass. However, not all accessions of late watergrass were digested with this enzyme. In contrast to EcoRI, the PCR product obtained using the trn-c and trn-d primer set was digested into two fragments by using AluI restriction enzyme in all accessions of late watergrass; whereas, it was not digested in barnyardgrass and early watergrass. This molecular differentiation among barnyardgrass, early watergrass, and late watergrass supports the hypothesis that late watergrass is not a synonym of early watergrass in Turkish accessions.

Experiments were conducted to study the effect of application rate, growth stage, and tank-mixing azimsulfuron or bentazon on the activity of cyhalofop, clefoxydim, and penoxsulam against two morphologically distinctEchinochloaspecies from rice fields in Greece. Mixtures of penoxsulam with MCPA were also evaluated. Cyhalofop (300 to 600 g ai/ha) applied at the three- to four-leaf growth stage provided 62 to 85% control of early watergrass but 41 to 83% control of late watergrass averaged over mixture treatments. Control ranged from 37 to 80% for early watergrass and from 35 to 78% for late watergrass when cyhalofop was applied at the five- to six-leaf growth stage averaged over mixture treatments. Mixtures of cyhalofop with azimsulfuron or bentazon reduced efficacy on both species irrespective of growth stage or cyhalofop application rate compared with cyhalofop alone. Clefoxydim (100 to 250 g ai/ha) applied alone at the three- to four-leaf growth stage provided 98 to 100% control of early watergrass and 91 to 100% control of late watergrass; when clefoxydim was applied alone at the five- to six-leaf growth stage the control obtained was 91 to 100% for early watergrass and 79 to 100% for late watergrass. Mixtures of clefoxydim with azimsulfuron or bentazon reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Penoxsulam (20 to 40 g ai/ha) applied alone provided 94 to 100% control of both species at both growth stages. Mixtures of MCPA with penoxsulam reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Mixtures of penoxsulam with azimsulfuron or bentazon reduced efficacy only on late watergrass at the late growth stage.

The photosynthetic responses of rice (C3) and threeEchinochloaspecies (C4), barnyardgrass, early watergrass, and late watergrass, to changes in CO2intercellular partial pressure, light intensity, and leaf temperature were investigated under laboratory conditions. The threeEchinochloaspecies exhibited photosynthetic responses characteristic of C4plants. The three weedy species showed higher efficiency for CO2utilization at low CO2intercellular partial pressure (CO2i) than rice. Compensation and saturation of CO2i for photosynthesis were lower in the weedy species than in rice. The maximum photosynthetic rates at high light intensity were 33.5, 32.7, 30.5, and 21.5 μmol CO2m-2s-1for barnyardgrass, early watergrass, late watergrass, and rice, respectively. Photosynthesis temperature optimum was 35 to 37 C for the threeEchinochloaspecies and 33 C for rice. Overall, under simulated summer conditions, the four taxa showed a photosynthetic ability hierarchy with regard to gas exchange performance as follows: barnyardgrass ≥ early watergrass > late watergrass > rice.

Experiments were conducted to evaluate the effect of application rate, growth stage, and tank mixing azimsulfuron, bentazon, MCPA, propanil, or cyhalofop on the efficacy of bispyribac–sodium against early watergrass and late watergrass from rice fields in northern Greece. Mixtures of bispyribac–sodium with the insecticides carbaryl, diazinon, and dichlorvos were also evaluated. Bispyribac–sodium (24 to 36 g ai/ha) applied alone at the three- to four-leaf growth stage provided 89 to 100% control of early watergrass and 84 to 100% control of late watergrass. When bispyribac–sodium was applied alone at the five- to six-leaf growth stage of early watergrass and late watergrass, control ranged from 78 to 100% and 71 to 100%, respectively. Mixtures of bispyribac–sodium with azimsulfuron provided better control of both species at any growth stage than bispyribac–sodium applied alone. On the contrary, mixtures of bispyribac–sodium with bentazon, MCPA, or propanil were less effective on both species at any growth stage than bispyribac–sodium applied alone. A slight efficacy reduction occurred on both species for the mixture of bispyribac–sodium with cyhalofop. Mixtures of bispyribac–sodium with the insecticides carbaryl or dichlorvos showed reduced efficacy on both species, whereas increased efficacy on both species was observed for mixtures of bispyribac–sodium with diazinon as compared with the single application of bispyribac–sodium.

Resistance to the thiocarbamates has been selected in early watergrass populations within the rice-growing region of California. To elucidate the processes contributing to the spread of resistance among rice fields, we characterized the genetic diversity and differentiation of thiobencarb-resistant (R) and thiobencarb-susceptible (S) populations across the Central Valley using microsatellite markers. A total of 406 individuals from 22 populations were genotyped using seven nuclear microsatellite primer pairs. Three analytical approaches (unshared allele, Shannon–Weaver, and allelic-phenotype statistics) were used to assess genetic diversity and differentiation in the allohexaploid species. Low levels of genetic variation were detected within populations, consistent with other highly selfing species, with S populations tending to be more diverse than R populations.FSTvalues indicated that populations were genetically differentiated and that genetic differentiation was greater among S populations than R populations. Principal coordinate analysis generated two orthogonal axes that explained 88% of the genetic variance among early watergrass populations and differentiated populations by geographical region, which was associated with resistance phenotype. A Mantel test revealed that genetic distances between R populations were positively correlated with the geographical distances separating populations. Taken together, our results suggest that both short- and long-distance seed dispersal, and multiple local and independent evolutionary events, are involved in the spread of thiobencarb-resistant early watergrass across rice fields in the Sacramento Valley. In contrast, resistance was not detected in early watergrass populations in the San Joaquin Valley.

In five field experiments from 1986 to 1988, herbicides were evaluated alone and in combinations for weed control in water-seeded rice. Combinations of bensulfuron with either molinate or thiobencarb applied into the paddy water at the 2-leaf stage of rice, controlled all broadleaf and sedge weeds, and 92% or more early watergrass. These combinations were equivalent to a commercial standard of molinate at the 2-leaf stage followed by a separate application of bentazon to the drained paddy at midtillering.

Questa tesi studia e valuta le tecniche agronomiche legate alla coltivazione del riso biologico nell'area del Nord Italia. Il finanziamento principale di questa tesi deriva dal progetto MIPAAF "Risobiosystems", iniziato nel 2017 e terminato nel 2020. Gli studi presentati sono collegati alla strategia europea di produzione alimentare sostenibile "Farm to Fork", che è il fulcro del Green Deal europeo per rendere i sistemi alimentari equi, sani e rispettosi dell'ambiente, incoraggiando l'espansione del settore dell'agricoltura biologica (Commissione europea 2020). Come riportato in letteratura, l'agricoltura biologica è in grado di ridurre l'impatto ambientale dell'agricoltura evitando l'uso di composti di sintesi (es. fertilizzanti, pesticidi) e favorendo pratiche (es. rotazione delle colture, leguminose, fertilizzanti organici, sovescio, verde pacciamatura.) in grado di aumentare lo stock di carbonio nel suolo e prevenire gli impatti ambientali indiretti dovuti alla produzione industriale di input (Acuna et al. 2018). Concentrandosi sul settore del riso, è stato osservato che il sistema organico è in grado di aumentare la capacità di stoccaggio del carbonio nel suolo (Komatsuzaki e Syuaib, 2010) e il contenuto di materia organica, facilitando la preparazione del suolo (Mendoza, 2004) e favorendo la successione ecologica e l'eterogeneità temporale delle comunità biologiche nel suolo (Martínez-Eixarch et al. 2017). Il lavoro di tesi una raccolta di articoli pubblicati o in corso di revisione, ogni capitolo riporta il mio contributo, e ogni connessione con altri lavori che sono stati avviati ed ancora in corso. Il capitolo I (https://doi.org/10.1016/j.agsy.2019.102739 ) rivela la mancanza di ricerca scientifica e informazioni sulla risicoltura biologica, soprattutto in Europa e in Italia. Lo studio presenta principalmente tre tecniche innovative di gestione delle erbe infestanti in risaia che possono essere considerate modelli adattabili nel loro contesto per la coltivazione del riso biologico. Questi modelli sono alla base di una lotta sostenibile contro i problemi ecologici e ambientali grazie al rigoroso divieto di sostanze chimiche come gli erbicidi. Nel lavoro emergono le metodologie la cui efficacia è stata ampiamente testata. In particolare la tecnica della “pacciamatura verde” utilizza colture di copertura (cover-crops) che controllano efficacemente le erbe infestanti grazie a quattro meccanismi principali. Il primo consiste nella parziale inibizione della germinazione delle erbe infestanti grazie alla competizione per l'acqua, i nutrienti e l'ombreggiamento, fenomeni causati dalla presenza di colture di copertura. La seconda consiste nell'effetto pacciamatura quando le cover-crops vengono sminuzzate o poste a terra con la semina del riso. Il terzo è rappresentato dai fenomeni di allelopatia che insorgono tra cover crops ed erbe infestanti (questo aspetto sarà approfondito nel Capitolo II, https://doi.org/10.3390/plants9030324 , https://doi.org/10.1007/s11356 -020-10140-4 ). Allo stesso tempo, il quarto meccanismo è legato all'accumulo di composti fitotossici a seguito della fermentazione provocata dall'acqua di immersione della risaia: l'ambiente anaerobico che si crea porta alla formazione di acidi organici come acido acetico, butirrico e propionico acido. L'allelopatia è un aspetto interessante offerto dalle piante in questa particolare agrotecnica. L'allelopatia generalmente produce e rilascia metaboliti secondari, generando effetti inibitori contro le specie vegetali vicine. La germinazione, la crescita e la riproduzione delle piante bersaglio possono così essere compromesse; questi aspetti sono stati approfonditi nel Capitolo II, partendo dall'esperienza degli agricoltori biologici. Lo studio mirava a definire l'azione inibitoria del Lolium multiflorum Lam., utilizzato come coltura di copertura prima della semina del riso nei confronti dell'Echinochloa oryzoides (Ard.) Fritsch è una delle principali infestanti del riso. Il Capitolo III si concentra sulla valutazione dell'impatto ambientale della coltivazione del riso biologico attraverso l'LCA considerando gli scenari produttivi e gli agrotecnici descritti nel Capitolo I. L'approccio LCA è stato adottato perché è largamente utilizzato per valutare l'impatto ambientale del processo agricolo. Tuttavia, da un punto di vista LCA, l'agricoltura biologica non è una risposta ovvia ai problemi ambientali perché LCA definisce la funzione del sistema studiato utilizzando una 'unità funzionale', che dovrebbe essere una misura precisa di ciò che il sistema offre ma non è in grado di considerare ad esempio effetti indiretti. Inoltre, studi LCA esprimono gli impatti per unità di un prodotto per impostazione predefinita. Tuttavia, l'agricoltura biologica generalmente emette meno inquinanti per unità di terra occupata rispetto all'agricoltura convenzionale (un approccio basato sulla superficie); può però avere impatti maggiori per unità di prodotto a causa delle sue rese inferiori per unità di superficie (van der Werf, 2020).
This thesis studies and evaluates the agronomical techniques associated with organic rice cultivation in the Northern Italy area. The study funding is from the Italian MIPAAF project "Risobiosystems", which started in 2017 and ended in 2020. The studies presented are connected to the European sustainable food production strategy "Farm to Fork," which is the core of the European Green Deal to make food systems fair, healthy and environmentally friendly, encouraging the expansion of the organic agriculture sector (European Commission 2020). As reported in the literature, organic farming is capable of reducing the environmental impact of agriculture by avoiding the use of synthetic compounds (e.g. fertilisers, pesticides) and by promoting practices (e.g. crop rotation, leguminous cultivation, organic fertilisers, green manure crops, green mulching.) able to increase the soil carbon stock, and prevent the indirect environmental impacts due to the industrial production of inputs (Acuna et al. 2018). Focusing on the rice sector, the organic system was observed able to increase the soil carbon storage capacity (Komatsuzaki and Syuaib, 2010) and organic matter content, facilitating the soil preparation (Mendoza, 2004) and promoting the ecological succession and temporal heterogeneity of the macrophyte communities into the soil (Martínez- Eixarch et al.; 2017). The thesis is a collection of articles published or under review associated with the organic rice production connected with Risobiosystems project results. Each paper explains my work and contribution, and each Chapter gave rise to new and ongoing studies. Chapter I (https://doi.org/10.1016/j.agsy.2019.102739) reveals the lack of scientific research and information about organic rice farming, especially in Europe and Italy. The studies mainly propose three different weed management techniques in the paddy field that can be considered models that can be standardised on farms specialising in their use. These models are the basis of a sustainable fight against ecological and environmental problems thanks to the strict avoidance of chemicals such as herbicides. Value is given to methodologies whose effectiveness has been widely tested. The green mulching technique uses cover crops that effectively control weeds thanks to four main mechanisms. The first consists of the partial inhibition of weeds' germination thanks to competition for water, nutrients, and shading, which are phenomena caused by the presence of cover crops. The second consists of the mulching effect when the crops are chopped or placed on the ground with rice sowing. The third is represented by the phenomena of allelopathy that arise between cover crops and weeds (this aspect will be further explored in Chapter II, https://doi.org/10.3390/plants9030324, https://doi.org/10.1007/s11356-020-10140-4 ). At the same time, the fourth mechanism is linked to the accumulation of phytotoxic compounds following the fermentation caused by the submersion water of the paddy field: the anaerobic environment that is created leads to the formation of organic acids such as acetic acid, butyric and propionic acid. Allelopathy is an interesting aspect offered by plants in this particular agrotechnical. Allelopathy generally produces and releases secondary metabolites, generating inhibitory effects against nearby plant species. The germination, growth and reproduction of target plants can thus be impaired; these aspects were deepened in Chapter II, starting from the organic farmers' experience. The study aimed to define the inhibitory action of Lolium multiflorum Lam., used as a cover crop before rice sowing against Echinochloa oryzoides (Ard.) Fritsch is one of the main rice weeds. Chapter III focuses on evaluating the environmental impact of organic rice cultivation through LCA considering the production scenarios and the agrotechnics described in Chapter I. The LCA approach was adopted because it is largely used to assess the environmental impact of the agriculture process. However, from an LCA viewpoint, organic agriculture is not an obvious answer to environmental problems because LCA defines the function of the studied system using a 'functional unit', which should be a precise measure of what the system delivers but is not able to consider for example indirect effects. Furthermore, LCAs express impacts per unit of a product by default. However, organic agriculture generally emits fewer pollutants per unit of land occupied than conventional agriculture (an area-based approach); it may have higher impacts per unit of product due to its lower yields per unit area (van der Werf, 2020).