Sub-lethal glyphosate exposure alters flowering phenology and causes transient male-sterility in Brassica spp

Abstract

BackgroundHerbicide resistance in weedy plant populations can develop through different mechanisms such as gene flow of herbicide resistance transgenes from crop species into compatible weedy species or by natural evolution of herbicide resistance or tolerance following selection pressure. Results from our previous studies suggest that sub-lethal levels of the herbicide glyphosate can alter the pattern of gene flow between glyphosate resistant Canola®, Brassica napus, and glyphosate sensitive varieties of B. napus and B. rapa. The objectives of this study were to examine the phenological and developmental changes that occur in Brassica crop and weed species following sub-lethal doses of the herbicides glyphosate and glufosinate. We examined several vegetative and reproductive traits of potted plants under greenhouse conditions, treated with sub-lethal herbicide sprays.ResultsOur results indicate that exposure of Brassica spp. to a sub-lethal dose of glyphosate results in altering flowering phenology and reproductive function. Flowering of all sensitive species was significantly delayed and reproductive function, specifically male fertility, was suppressed. Higher dosage levels typically contributed to an increase in the magnitude of phenotypic changes.ConclusionsThese results demonstrate that Brassica spp. plants that are exposed to sub-lethal doses of glyphosate could be subject to very different pollination patterns and an altered pattern of gene flow that would result from changes in the overlap of flowering phenology between species. Implications include the potential for increased glyphosate resistance evolution and spread in weedy communities exposed to sub-lethal glyphosate.

Decay characteristics and erosion-related transport of glyphosate in Chinese loess soil under field conditions

“…Erosive rainfall occurs frequently in regions with loess soil in China (Shi and Shao, 2000), and many nutrients and pesticides are transported, leading to serious water pollution (Li et al, 2011;Ongley et al, 2010). Glyphosate in soil either can be dispersed in runoff and drainage or carried with soil particles (Avigliano et al, 2014;Bergstrom et al, 2011;Kjaer et al, 2005;Lanctot et al, 2013;Londo et al, 2014;Styczen et al, 2011;Webster et al, 2014). Many studies have documented the transport of glyphosate by runoff and leached discharge, but most have focused on laboratory and lysimetric methods using pots or soil columns (Bergstrom et al, 2011;Zhao et al, 2009;Zhou et al, 2010).…”

“…The dynamics of soil moisture caused by heavy rains would likely indirectly affect glyphosate decay and transport with preferential flow (Coupe et al, 2012;Degenhardt et al, 2012;Todorovic et al, 2014), which would increase the risk to nearby water bodies, soils, and aquatic life (Avigliano et al, 2014;Lanctot et al, 2013;Londo et al, 2014;Webster et al, 2014). Erosive rainfall occurs frequently in regions with loess soil in China (Shi and Shao, 2000), and many nutrients and pesticides are transported, leading to serious water pollution (Li et al, 2011;Ongley et al, 2010).…”

Plant reproduction is altered by simulated herbicide drift to constructed plant communities

“…The reduction in flowering decreased the likelihood that these plants would be pollinated by transgenic B. rapa genotypes, thereby potentially reducing their susceptibility to gene flow, and also reduced the number of B. rapa L. seeds available in the soil seed bank. Londo et al also indicated that sublethal (0.05–0.1× f.a.r.) exposure to glyphosate resulted in deformed and shortened anthers, which appeared unable to release pollen normally.…”

Shifts in outcrossing rates and changes to floral traits are associated with the evolution of herbicide resistance in the common morning glory

“…; Londo et al . ) and can have long‐term evolutionary consequences on these non‐target species. In the USA, 40% of the pesticides applied across the 400 million acres of cropland are herbicides ( US EPA ), which impose extreme selection on naturally occurring agricultural weeds (Jasieniuk et al .…”