Evaluation of Rigid Ryegrass (Lolium rigidum) accessions for clodinafop-propargyl Resistance using bioassay in Petri dish and pot

Abstract

Three rigid ryegrass accessions with possible resistance to clodinafop-propargyl, anacetyl-CoA carboxylase (ACCase) inhibitor (group 1) herbicide were identified in Farsprovince fields. Greenhouse studies and seed bioassay experiments were conducted toconfirm clodinafop-propargyl resistance in Lolium rigidum L. In Petri dish seed bioassay testwere determined the coleoptiles length of accessions (as % of untreated control), ID50(dosage required to inhibit coleoptile length by 50%), the degree of resistance in S and Raccessions. In greenhouse experiments to determine the degree of resistance, accessions wereexposed to clodinafop-propargyl at 4-leaf stage. Four weeks after spraying was calculated thedry weight of accessions (%), plant survival of each accession (% of untreated control) andevaluation was performed according to EWRC. Then, the responses of accessions exposed to0.25 to 32 times the recommended dosage of clodinafop-propargyl was measured and thedegree of resistance in S and R accessions was identified. Results of bioassay andgreenhouse studies revealed that in both experiments and for parameters measured FR1accession showed more resistance than the other accessions, followed by FR7 and Saccessions, respectively. So these two methods tested can be used to help assess the degree ofresistance and reached the same result with two methods.