Genetic diversity and spread of glyphosate-resistant flaxleaf fleabane

Abstract

BackgroundContinual application of herbicides for flaxleaf fleabane control readily results in the evolution of herbicide resistance. Flaxleaf fleabane has evolved resistance to different modes of action herbicides in many countries. Due to the comprehensive geographical distribution of flaxleaf fleabane in Australia, it was classified as a cosmopolitan weed and it therefore has no specific climatic requirement.ResultsThe high percentage of polymorphisms in the samples of the susceptible population (79.8%, 75%) suggests that susceptible populations of flaxleaf fleabane, even within one site, originated from a number of parents. However, the percentage of polymorphism in the resistant populations (51.5%, 66.8%) suggests that resistant populations of flaxleaf fleabane within one site could have originated from fewer parents. In addition, any site containing resistant and susceptible populations of flaxleaf fleabane may have been populated by a large number of parents, evidenced by the relatively high percentage of polymorphisms detected by amplified fragment length polymorphism (AFLP) analysis (86.5%). Despite the large geographic distances between collection locations, populations from across states clustered in several groups showing a close genetic relationship among these populations over these large distances. These high levels of genetic diversity within and between populations confirmed in the sequencing of enolpyruvylshikimate-3-phosphate above support the results of AFLP studies and gave the author more confidence to report the genetic diversity seen within and between population studies.ConclusionTo prevent further resistance spread, flaxleaf fleabane management in infested areas should focus on decreasing seed movement from resistant sites as well as reducing the selection pressure for resistance to glyphosate by adopting alternative management strategies.