Mechanisms that may lead to high genetic divergence and to the invasive success of tall fleabane (Conyza sumatrensis; Asteraceae)

Abstract

Tall fleabane [Conyza sumatrensis (Retz.) E. Walker] is commonly invasive in agricultural fields, reducing yield in various infested crops. The current study investigates the genetic diversity within and between a significant number of invasive C. sumatrensis biotypes in soybean fields in southern, southeastern and midwestern Brazil, using microsatellites as molecular markers. High and low observed and expected heterozygosity estimated in microsatellite loci supported our hypothesis that different levels of genetic diversity may be detected within biotypes from different invaded fields. Analysis of a significant number of biotypes in several fields showed high and low genetic diversity not associated with the geographic distribution, bottleneck effect and susceptibility to glyphosate. A deficit of heterozygous plants, high genetic divergence and moderate allele transference were also observed. Allele fixation was different in the different biotypes. The bottleneck effect was seen in biotypes with reduced genetic diversity and in biotypes with highest genetic diversity. Data on genetic diversity, bottleneck effect, and glyphosate resistance showed contrasts in biotypes from nearby invaded fields. Our study showed different genetic diversity levels in biotypes from invaded areas under the same climatic conditions.

Identification, mapping, and chemical control of fleabane resistant to glyphosate, chlorimuron, paraquat, and 2,4-D

“…In Brazil, the first cases of glyphosate-resistant hairy fleabane and horseweed were recorded in 2005, while the first case of glyphosate-resistant Sumatran fleabane was recorded in 2010 (Heap 2023). There is a higher prevalence of Sumatran fleabane in Brazil, although hairy fleabane also occurs, especially in southern Brazil (Marochio et al 2017; Ruiz et al 2022). Cases have been reported of Sumatran fleabane with resistance to paraquat (Zobiole et al 2019); 2,4-D (Queiroz et al 2020); glyphosate, chlorimuron, and saflufenacil (Heap 2023); and multiple resistance to chlorimuron and glyphosate (Santos et al 2014a); chlorimuron, glyphosate, and paraquat (Albrecht et al 2020a); and 2,4-D, diuron, glyphosate, paraquat, and saflufenacil (Pinho et al 2019).…”