Biological Cycle of Susceptible and Glyphosate-Resistant Sourgrass Biotypes in Two Growth Periods

Abstract

Selecting glyphosate-resistant Digitaria insularis may cause changes in the biological cycle of the species. Therefore, the objective of this study was to evaluate the biological cycle of susceptible and glyphosate-resistant D. insularis biotypes in two growth periods (summer/autumn and autumn/winter). Seeds were collected in the municipality of Alagoa Grande (07o02’59" S 35o37’01,5" W), and were considered susceptible (S1), in Cascavel (24o55’27" S 53o27’54.6 ”W) considered as resistant 1 (R1), Entre Rios do Oeste (24o40’44" S 54o17’05" W) considered as resistant 2 (R2) and Marechal Cândido Rondon (24o42’30" S 54o21’10" W) considered as resistant 3 (R3). Evaluations were carried out in the summer/autumn and autumn/winter periods. The collection periods of plants were: 14; 21; 28; 35; 42; 49; 56; 63; 70; 77; 84; 91; 98; 105; 112 and 119 days after emergence (DAE). The selection of glyphosate-resistant D. insularis biotypes in agricultural areas affected the biology of the species, in relation to the original population of the susceptible biotype. In the summer/autumn period (mean temperature 24.6 oC), the S biotype started the emission of tillers and flowering at 14 and 21 DAE on an average, respectively, before the resistant biotypes. However, in the autumn/winter period (mean temperature 19.0 oC) only the R1 biotype was able to develop and complete the biological cycle. The evaluated biotypes presented differences during the development, mainly between the phenological stages, so that the susceptible biotype was the most precocious and with a high reproductive potential. The physiological evaluations showed no differences among the S, R1, R2 and R3 biotypes, as verified in the TCR.

Weed coexistence periods in cassava varieties

“…It is noteworthy that the weeds with higher RI observed in this experiment are all difficult to be controlled, mainly because they are resistant to herbicides such as glyphosate and other mechanisms of action (Takano et al, 2016;Ferreira et al, 2018).…”

Chemical and cultural management strategies for glyphosate-resistant sourgrass in central Brazil

“…In Brazil, glyphosate-resistant sourgrass was first reported in 2008 in the state of Paraná (Heap, 2022). This led to several studies aiming to understand the dynamics of biotypes of the species, focusing on their biology or management (Martins et al, 2017;Pereira et al, 2017;Ferreira et al, 2018;Marochi et al, 2018;Silveira et al, 2018). In agricultural fields, treatments based on ACCase-inhibiting herbicides, such as clethodim and haloxyfop-p-methyl, became the most applied because they were considered effective for the control of adult glyphosate-resistant sourgrass plants when combined or not with other management strategies (Cassol et al, 2019;Mendes et al, 2020;Nunes et al, 2021;Raimondi et al, 2020;.…”

Sourgrass phenological stage and efficacy of ACCase-inhibiting herbicides

“…They can form rhizomes that are short, but evident, forming pronounced clumps. These plants have a fast growth, production of large number of seeds, and high seed dissemination capacity during the whole summer (Gemelli et al, 2012;Ferreira et al, 2018).…”