Crescimento diferencial de biótipos de Conyza SPP. resistente e suscetível ao herbicida glifosato

Abstract

resistente e suscetível ao herbicida glifosato, a fi m de quantifi car os efeitos da pressão de seleção para resistência nos biótipos. Dois experimentos foram desenvolvidos com tratamentos organizados em esquema fatorial 9 x 2, com nove avaliações periódicas de crescimento e dois biótipos de cada espécie. As variáveis avaliadas por planta foram: área foliar; massa seca da parte aérea, das raízes e total, obtendo-se, a partir desta última, a taxa de crescimento absoluto. O biótipo de C. canadensis resistente ao glifosato possui crescimento mais lento, menor acúmulo de área foliar e de massa seca que o biótipo suscetível. Menores áreas foliar e massa seca também foram registradas para o biótipo de C. bonariensis resistente ao glifosato quando comparado ao suscetível, porém com diferenças mais sutis que aquelas constatadas para C. canadensis. O crescimento absoluto do biótipo suscetível foi superior ao do resistente em ambas as espécies. A pressão de seleção para resistência ao glifosato teve impactos negativos na habilidade de crescimento dos biótipos.Palavras-chave: buva, resistência, desenvolvimento, ecologia, populações. ABSTRACT DIFFERENTIAL GROWTH OF GLYPHOSATE-RESISTANT AND SUSCEPTIBLE BIOTYPES OF CONYZA SPP.This work was carried out with the objective of comparing, under controlled and non-competitive condition, the growth of glyphosate-resistant and susceptible biotypes of Conyza canadensis and C. bonariensis; to quantify the effects of resistance selection pressure on the biotypes. Two trials were developed with treatments organized according to a factorial scheme 9 x 2, where nine were periodical growth evaluations and two were biotypes of each species. The variables evaluated per plant were: leaf area and dry mass (shoot, root and total); to determine absolute growth rate from the total dry mass. The glyphosate-resistant biotype of C. canadensis exhibits slower growth and smaller accumulation of leaf area and dry mass than the susceptible biotype. Lower leaf area and dry mass were also registered for the glyphosate-resistant biotype of C. bonariensis when compared to the susceptible one, however with more subtle differences than those identifi ed for C. canadensis. Absolute growth rate of susceptible biotype was superior to that of resistant ones for both species. The pressure of selection to glyphosate resistance had negative impacts on the biotype growth.

Weed Occurrence in Sugarcane as Function of Variety and Ground Straw Management1

“…In 2012, only 1049 without straw removal from planting rows differed from the other treatments by the exclusive occurrence of wild poinsettia as a weed. The similarity between treatments with straw removal from planting rows (T2) and without straw removal from planting rows (T1) in the first year was of 50%, which is considered high by the Jaccard coefficient (Mueller Dombois & Ellenberg, 1974), with 33% of similarity between this cluster (T1 + T2) and 1049 under straw removal from planting rows (T4) (Figure 3), which is also considered similar by the same coefficient. In 2013, the clustering reliability was not enough to allow inferences (cophenetic correlation below 0.85), being thus not considered.…”

“…Variety 1049 without straw removal from planting rows was infested with four weed species, especially wild poinsettia and horseweed, the latter constituting a cosmopolitan species resistant to herbicide glyphosate, widely distributed throughout the Central-West Region of Brazil, difficult to control, drought-tolerant and with a large production of seeds (Kissmann & Groth, 1999;Wu & Walker, 2006;Moreira et al, 2010).…”

Características fisiológicas de biótipos de Conyza bonariensis Resistentes ao glyphosate cultivados sob competição

“…No mesmo estudo, o biótipo suscetível apresentou menor tendência de redução dessas variáveis com o incremento da intensidade de competição. Moreira et al (2010) observaram que o biótipo de C. canadensis resistente ao herbicida glyphosate demonstrou crescimento mais lento e menor acúmulo de área foliar e de massa seca que o suscetível, e o crescimento absoluto do biótipo suscetível foi superior ao do resistente.…”

Photosynthetic Performance of Glyphosate Resistant and Glyphosate Susceptible Hairy Fleabane under Light Intensity

“…Under non-competitive conditions, glyphosate-susceptible biotypes of C. bonariensis and C. canadensis presented higher absolute growth than the resistant biotypes, which means that glyphosate-resistant plants had a negative performance in terms of development capacity (Moreira et al, 2010). On the other hand, for glyphosate-resistant C. canadensis, there was a quicker initial development than the susceptible biotype, and under conditions of water deficit, it was more competitive (Shrestha et al, 2010).…”

“…Studies have identified that glyphosate-resistant biotypes do not present costs in the adaptation under competitive and non-competitive conditions (Travlos and Chachalis, 2013;Shrestha et al, 2014). Other studies demonstrated that the absolute growth of biotype S was higher than biotype R for C. canadensis and C. bonariensis coming from citrus orchard areas (Moreira et al, 2010). On the other hand, studies with C. bonariensis biotypes coming from RR soybean production areas in Rio Grande do Sul allowed inferring that biotype R has better competitive abilities, compared with biotype S (Kaspary et al, 2014(Kaspary et al, , 2015.…”