Suscetibilidade de genótipos de Lolium multiflorum ao herbicida glyphosate

Abstract

RESUMO -Objetivou-se com este trabalho avaliar o grau de tolerância dos genótipos diploides e tetraploides de L. multiflorum (azevém) ao herbicida glyphosate. Para isso, foram instalados quatro experimentos, sendo um para cada estádio fenológico do azevém (duas folhas, quatro perfilhos, pré-florescimento e formação de grãos). Utilizou-se delineamento em blocos casualizados com arranjo fatorial 2 x 6 (dois genótipos e seis doses do herbicida glyphosate: 240, 480, 960, 1.920, 3.840 e 7.680 g e.a. ha ) e uma testemunha sem aplicação de glyphosate, com quatro repetições. Os parâmetros analisados foram porcentagem de controle e fitomassa seca da parte aérea das plantas. Os resultados foram submetidos à análise de variância e, em seguida, ajustados para modelo de curva de dose-resposta do tipo logística, sendo desses modelos calculados valores de controle correspondentes a 50, 80, 90 e 99%. Os genótipos de azevém diploide apresentaram suscetibilidade diferencial ao herbicida glyphosate, sendo o genótipo tetraploide mais tolerante ao herbicida que o diploide. O grau diferencial de tolerância, medido pelo fator de tolerância diferencial entre os genótipos, foi de 1,6 vez a dose de glyphosate no genótipo tetraploide em relação ao diploide. Os estádios fenológicos de desenvolvimento das plantas de ambos os genótipos afetaram o grau de tolerância ao glyphosate. A variável fitomassa seca das plantas apresentou a mesma tendência diferencial entre os genótipos diploides e tetraploides que o parâmetro porcentagem visual de controle. Palavras-chave: azevém, inibidor da ESPS, herbicida.ABSTRACT -This work aimed to evaluate the degree of tolerance of Italian ryegrass genotypes to the herbicide glyphosate. Thus, four experiments were installed, one for each phenological stage (two leaves, four tillers, pre-flowering, and grain formation). The treatments consisted of the combination of the two genotypes and six rates of glyphosate (240; 480; 960; 1,920; 3,840 and 7,680 g a.e. ha ) and a check without glyphosate application, in a complete randomized block design and four replications. The parameters analyzed were control percentage and shoot dry biomass. Results were submitted to analysis of variance and subsequently adjusted to non-linear log of dose-response curves, and from these models control values were calculated at 50, 80, 90 and 99%. The Italian ryegrass genotypes presented differential susceptibility to the herbicide glyphosate, with the tetraploid genotype being more tolerant to the herbicide than the diploid. The degree of differential tolerance, measured by the differential tolerance factor between the genotypes, is 1.6 times the glyphosate dose in the tetraploid genotype compared to the diploid genotype. The phenological stages of plant development of both the genotypes studied affected the degree of tolerance to glyphosate. The variable shoot dry biomass presented the same differential tendency between the diploid and tetraploid genotypes presented by the parameter visual control percentage.

Ryegrass control derived from isolated application with herbicides association

“…ha -1 , rising to 87% at a 1440 g e.a. ha -1 dose and reaching 90% at a 2160 g e. a. ha -1 dose, characterizing control efficiency with the increase of this herbicide dose, which corroborates with DORS et al (2010) data, who working with different glyphosate rates, and tworyegrass genotypes (diploid and tetraploid), observed an increase in the control level by increasing glyphosate herbicide dose. These results show that although requiring high doses, the evaluated ryegrass biotype is sensitive to glyphosate.…”

“…In addition, weed species respond differently to herbicides when isolated or in combination (BARROSO et al, 2010) and in different weed plant stages. The more advanced the stage is, higher will be the herbicide dose required for an efficient control (DORS et al, 2010). Glyphosate is registered to control ryegrass at doses between 720 and 2160 g of acid equivalent (a.e.)…”

Influence of Density and Development Stage of Ryegrass on Glyphosate Effectiveness

“…Other studies also demonstrate a similar effect. Ryegrass plants sprayed with glyphosate showed that the control at the two-leaf stage was 67% higher when compared to plants treated at the tillering stage with the same herbicide dose (Dors et al, 2010). Plants of Eleusine indica at the two-leaf stage sprayed with glyphosate obtained a control 66% higher than that observed on plants treated at the tillering stage (Ulguim et al, 2013).…”

Caracterização Morfoanatômica, Contagem Cromossômica E Viabilidade Polínica De Biótipos De Azevém Suscetível E Resistentes Ao Herbicida Glyphosate

“…Há relatos de que o azevém diploide apresenta suscetibilidade diferencial ao herbicida glyphosate, porém o tetraploide se mostra mais tolerante, fato que pode explicar o controle insatisfatório da planta daninha nas áreas de cultivo. Entretanto, o estádio fenológico de desenvolvimento das plantas pode afetar o grau de tolerância ao glyphosate em ambos os genótipos (Dors et al, 2010).…”