Resistance benefit endowed by a double EPSPS glyphosate resistance mutation (TIPS) in Eleusine indica

VILA AIUB, MM; JALALUDIN, A; HAN, HEPING; POWLES, SB; GARCÍA, FEDERICO; YU, QIN

Congreso; Resistance'19 Rothamsted; 2019

A known single (P106S)and novel double (TIPS) glyphosate resistance point mutations have beenidentified in Eleusine indica. Experimentswere conducted to assess the plant resistance benefit endowed by these specificTIPS (homozygous RR vs heterozygous Rr) and P106S mutations.  The P106Smutation gives modest 50% survival under glyphosate field dose with survivingplants showing a significant reduction in vegetative and reproductive growth,compared to untreated plants. The RR TIPS variant endows 100% survival underglyphosate treatment and no significant impact on reproductive growth isobserved. An even higher resistance fitness benefit is associated with thecompound heterozygous Rr TIPS plants. Although both RR and Rr TIPS plants showno plant mortality under glyphosate treatment, vegetative and reproductivegrowth is significantly higher in Rr than in RR TIPS plants. Rapid herbicideresistance evolution is expected when resistance mutations endow highresistance benefits under herbicide selection.  Based on theseresults, the homozygous RR TIPS resistance alleles are expected to rapidlyincrease and be fixed in E. indicapopulations under glyphosate selection. Whereas, the homozygous P106S alleles areexpected to increase at a lower rate given the low/moderate fitness benefitwhen glyphosate challenged. This hypothesis is currently under empirical analysis.