Mudanças morfofisiológicas e metabólicas em biótipos de azevém, resistente ou suscetível a glyphosate em competição com soja.

Abstract

Soybean (Glycine max) is the most grown oilseed worldwide, it is cultivation is depending on the usage of herbicides for the control of weeds , in a response to the handling methods applied, the evolution of resistant weed population has occurred. For the past few years the producers have observed difficulties in the control of ryegrass (Lolium multiflorum) with glyphosate herbicide. The goals of the research were to determine the C50 and GR50 of the subject resistant biotype, in relation to the susceptible biotype; to investigate the relative competitive ability between resistant and susceptible ryegrass biotypes and of these with soy cultures; and, to verify the changes in secondary compounds and cell damage in soy plants and of the ryegrass biotypes resistant and susceptible to glyphosate, when in competition. The results show that for control the resistant biotype demands doses superior to 40 times those demanded by the susceptible biotype. The soybean culture presents equivalent competitiveness to the susceptible ryegrass biotype and inferior to the resistant biotype, whilst the biotypes, both susceptible and resistant to glyphosate, present equivalent competitive ability. In general, for the soybean culture the production of secondary compounds, as well as the oxidative damages, were superior as a result of the interspecific competition. The biotypes, the susceptible as well as the resistant, did not display changes in the production of secondary metabolites and oxidative damage when competing between each other and with the soybean culture.