Temperature influences the level of glyphosate resistance in barnyardgrass (Echinochloa colona)

Abstract

There is reduced efficacy of glyphosate at high temperatures on resistant E. colona populations, making these populations harder to control in summer.

Multiple target site resistance to glyphosate in junglerice (Echinochloa colona) lines from California orchards

“…Previous studies on glyphosate resistant populations of E. colona have detected target site mutations (TSMs) at Pro106 of the EPSPS gene. A Pro106Ser substitution was present in resistant E. colona populations from a maize field in California and from Australia which showed RIs of 6.6, 2.1 and 4.7 respectively. A Pro106Thr identified in a population from California and Australia resulted in RIs of 3.9 and 2.2 respectively and a Pro106Leu/Thr in a population from Australia had an RI of 1.28 …”

Target‐site mutations conferring resistance to glyphosate in feathertop Rhodes grass (Chloris virgata) populations in Australia

“…Glyphosate efficacy can be reduced by a number of environmental conditions, including high air temperature, low soil moisture content and low relative humidity . Echinochloa colona control with glyphosate was greater at 20–25 °C than at 30–35 °C . This difference in plant response was related to reduced glyphosate absorption in E. colona when air temperature increased .…”

“…The shikimate assay using excised leaf discs eliminates the contributions of absorption through the leaf cuticle and translocation of glyphosate to the leaf cells in assessing whether glyphosate inhibits EPSPS. The leaf disc assay is only affected by the ability of glyphosate to penetrate into the chloroplast and the tolerance of the target enzyme . There was significantly greater shikimate accumulation in plants of CV7 than in V15 and V14.2 at all glyphosate concentrations used, indicating that glyphosate did reach the target site and inhibited the EPSPS enzyme of each population differently .…”

High carbon dioxide concentration and elevated temperature impact the growth of weeds but do not change the efficacy of glyphosate

“…It is probable that the impact of high CO 2 concentration on weeds is greater under weed–crop competition than for weeds growing alone . In previous studies, elevated temperature was found to have the potential to decrease the sensitivity of weeds to glyphosate; however, such effects were associated with susceptibility or resistance of a weed to glyphosate . In contrast to glyphosate‐susceptible weeds, glyphosate‐resistant weeds were found to decrease their herbicide sensitivity as a result of a mutation which occurred only in resistant weed populations .…”