Induced novel psbA mutation (Ala₂₅₁ to Thr) in higher plants confers resistance to PSII inhibitor metribuzin in Lens culinaris

Abstract

BACKGROUND Weed competition is a major limitation to worldwide lentil (Lens culinaris Medik.) production in part due to limited effective safe herbicide options. Metribuzin is a photosystem II inhibiting herbicide that provides broad spectrum weed control, however it causes excessive injury in lentil. Dose response analysis of photosystem II inhibiting herbicides and DNA sequencing of the psbA chloroplast gene occurred to quantify the spectrum and mechanism of herbicide resistance in two ethyl‐methanesulfonate (EMS) induced mutant lentils. RESULTS Compared to susceptible parent PBA Flash, the level of metribuzin resistance was 33‐fold for mutant M043 and 10‐fold for M009. No improvement in resistance occurred in either mutant to bromoxynil, diuron, bromacil and atrazine herbicides. Nucleotide sequencing of the psbA gene of both mutants identified a substitution at position 751 compared to PBA Flash. The resulting deduced amino acid sequence indicated an Ala251Thr substitution as being most likely responsible for the high level of metribuzin resistance. CONCLUSIONS The Ala251Thr substitution discovered in this study is unique in mutagenized higher plants and the first report of an induced psbA target site mutation in higher plants. This target site metribuzin resistance is likely to have a significant impact on lentil production in Australia and worldwide. © 2019 Society of Chemical Industry

CRISPR/Cas9 gene editing in legume crops: Opportunities and challenges

“…Chickpeas are sensitive to many postemergent herbicides registered for the control of broadleaf weeds in lentils or peas. The recent discovery of the Ala 251 Thr substitution in psbA chloroplast gene being responsible for resistance to a photosystem II inhibitor herbicide metribuzin (McMurray et al, 2019) has opened this a new avenue for creating herbicide resistance in chickpea and other legumes using gene editing. In another study, the identification and expression analysis of candidate genes involved in carotenoid biosynthesis in chickpea (Rezaei et al, 2016) has revealed several candidate genes as early knockout targets for improving carotenoid content in chickpea.…”