Fitness of Echinochloa crusgalli var. mitis biotypes susceptible and resistant to imazapyr + imazapic herbicide

The continuous use of herbicides with the same mechanism of action has caused the selection of resistant weed biotype that may present differences in fitness when compared with susceptible biotype. The objective of the present study was to identify and distinguish the fitness of barnyardgrass biotypes resistant and susceptible to imazapyr + imazapic herbicide under controlled and noncompetitive conditions. For that, there were used barnyardgrass biotype susceptible (ECH1 and ECH38) and resistant (ECH14 and ECH44) to ALS inhibitors, collected at Pelotas/RS and Rio Grande/RS cities, respectively, in experiment installed in a greenhouse in a completely randomized experimental design during the months from October to December 2015. The biotype were evaluated during the period of 15 to 120 days after the emergence related to plant height, foliar area, shoot dry matter mass and root dry matter mass. The results showed insignificant differences between the biotypes during the development of the plants. The susceptible biotype ECH44 showed a higher number of panicles per plant and seeds along with the resistant ECH1. There is variability among Echinochloa crusgalli var. mitis biotypes resistant and susceptible to ALS inhibitors, indicating an absence in fitness penalty caused by resistance when cultivated without the selection of pressure (herbicide).The continuous use of herbicides with the same mechanism of action has caused the selection of resistant weed biotype that may present differences in fitness when compared with susceptible biotype. The objective of the present study was to identify and distinguish the fitness of barnyardgrass biotypes resistant and susceptible to imazapyr + imazapic herbicide under controlled and noncompetitive conditions. For that, there were used barnyardgrass biotype susceptible (ECH1 and ECH38) and resistant (ECH14 and ECH44) to ALS inhibitors, collected at Pelotas/RS and Rio Grande/RS cities, respectively, in experiment installed in a greenhouse in a completely randomized experimental design during the months from October to December 2015. The biotype were evaluated during the period of 15 to 120 days after the emergence related to plant height, foliar area, shoot dry matter mass and root dry matter mass. The results showed insignificant differences between the biotypes during the development of the plants. The susceptible biotype ECH44 showed a higher number of panicles per plant and seeds along with the resistant ECH1. There is variability among Echinochloa crusgalli var. mitis biotypes resistant and susceptible to ALS inhibitors, indicating an absence in fitness penalty caused by resistance when cultivated without the selection of pressure (herbicide)

Ecophysiology of forage and annual ryegrass seed production under defoliation

The aim of the study was to evaluate the impact of defoliation frequency on the structural characteristics of plants for both forage production and seed production. The yield responses of different cultivars of annual ryegrass (Lolium multiflorum Lam.), BRS Ponteio and BRS Estações, were related to environmental variables, especially the thermal sum, to verify the morphophysiological dynamics of the plants. The present study was conducted in the field, in southern Brazil, at Embrapa Clima Temperado (ETB). Structural characteristics (number of tillers and leaves, average length of the live fraction of the leaf, heights of the last blade and ligule and leaf layer) were evaluated using the marked tiller technique; forage yield, structural components (blade, sheath plus stem and dead material), nutritive value of the harvested forage (crude protein and fiber insoluble in neutral detergent), yield and physiological quality of the seed (germination, purity, weight of a thousand seeds, emergence field, accelerated aging, root and shoot weight and length). Defoliation during the vegetative period provided forage harvesting of high nutritional value and did not affect the structure of the plant for seed production. The seeds produced showed greater weight. Defoliation soon after intense internode elongation (mid-September) determined very different structures after defoliation, however, yield and seed quality remained high. The main change in the plant, verified at the time of seed harvest, was the increase in the number of basic tillers. However, these tillers presented smaller structural variables (number of leaves, average length of the live fraction of the leaf, heights of the last blade and ligule and leaf layer). Subsequent defoliation determines drastic reductions in plant structure and, above all, in seed yield. In general, the two cultivars studied showed seeds with high physiological quality, even when subjected to high frequency of defoliation, which occurred even after the flowering of the plants.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESO objetivo do estudo foi avaliar o impacto da frequência da desfolha nas características estruturais das plantas tanto para a produção de forragem quanto para a produção de sementes. As respostas produtivas de diferentes cultivares de azevém anual (Lolium multiflorum Lam.), BRS Ponteio e BRS Estações, foram relacionadas a variáveis ambientais, especialmente a soma térmica, para a verificação da dinâmica morfofisiológica das plantas. O presente estudo foi conduzido à campo, no sul do Brasil, na Embrapa Clima Temperado (ETB). Foram avaliadas características estruturais (número de perfilhos e de folhas, comprimento médio da fração viva da folha, alturas da última lâmina e lígula e camada de folhas) por meio da técnica de perfilhos marcados; rendimento de forragem, componentes estruturais (lâmina, bainha mais colmo e material morto), valor nutritivo da forragem colhida (proteína bruta e fibra insolúvel em detergente neutro), rendimento e qualidade fisiológica da semente (germinação, pureza, peso de mil sementes, emergência em campo, envelhecimento acelerado, peso e comprimento de raiz e de parte aérea). A desfolha durante o período vegetativo propiciou colheita de forragem de alto valor nutritivo e não afetou a estrutura da planta para a produção de sementes. As sementes produzidas apresentaram maior peso. Desfolhas logo após o intenso alongamento dos entrenós (meados de setembro) determinaram estruturas muito distintas após a execução da desfolha, porém, o rendimento e a qualidade de sementes se mantiveram elevados. A principal alteração da planta, verificado no momento da colheita de sementes, foi o aumento do número de perfilhos basilares. Todavia estes perfilhos apresentaram variáveis estruturais de menor dimensão (número de folhas, comprimento médio da fração viva da folha, alturas da última lâmina e lígula e camada de folhas). Desfolhas posteriores determinam reduções drásticas na estrutura das plantas e, sobretudo, no rendimento de sementes. De modo geral, as duas cultivares estudas, apresentaram sementes com alta qualidade fisiológica, mesmo quando submetidas a alta frequência de desfolha, as quais ocorreram inclusive após o florescimento das plantas

Fitness of Echinochloa crusgalli var. mitis biotypes susceptible and resistant to imazapyr + imazapic herbicide

The continuous use of herbicides with the same mechanism of action has caused the selection of resistant weed biotype that may present differences in fitness when compared with susceptible biotype. The objective of the present study was to identify and distinguish the fitness of barnyardgrass biotypes resistant and susceptible to imazapyr + imazapic herbicide under controlled and noncompetitive conditions. For that, there were used barnyardgrass biotype susceptible (ECH1 and ECH38) and resistant (ECH14 and ECH44) to ALS inhibitors, collected at Pelotas/RS and Rio Grande/RS cities, respectively, in experiment installed in a greenhouse in a completely randomized experimental design during the months from October to December 2015. The biotype were evaluated during the period of 15 to 120 days after the emergence related to plant height, foliar area, shoot dry matter mass and root dry matter mass. The results showed insignificant differences between the biotypes during the development of the plants. The susceptible biotype ECH44 showed a higher number of panicles per plant and seeds along with the resistant ECH1. There is variability among Echinochloa crusgalli var. mitis biotypes resistant and susceptible to ALS inhibitors, indicating an absence in fitness penalty caused by resistance when cultivated without the selection of pressure (herbicide)