Germination fitness differs between penoxsulam resistant and susceptible Echinochloa phyllopogon biotypes

Echinochloa phyllopogon , a malignant weed that mostly reproduces through self-pollination in the paddy fields of Northeast China, currently presents critical resistance concerns. Multiple herbicide-resistant individuals were identified within the same population, and seed from each biotype were propagated for three generations. Three biotypes resistant to penoxsulam showed varying degrees of cross-resistance to other acetolactate synthase ( ALS ) inhibitors. The sequencing results indicated that the F4 generation seeds were homozygous with stably inherited mutations. A derived cleaved amplified polymorphic sequences (dCAPS) method is consistent with the sequencing results and can be used to quickly and accurately detect specific ALS mutations in E. phyllopogon . Sseed germination experiments revealed that R NTSR (non-target-site resistance) and R 197 biotypes exhibited significant germination fitness costs under certain extreme environmental conditions. At 200 mM NaCl concentration, the t E 50 values of R NTSR and R 197 were 11.37 and >14 days, respectively, with the mean germination times of 10.32 and 8.66 days, both longer than those of the sensitive (S) biotype. Under osmotic potential and soil burial conditions, the R NTSR biotype showed a reduced germination and emergence than the S biotype. Overall, the R NTSR and R 197 biotypes exhibit significant germination fitness costs under certain extreme environmental conditions, including temperature, salt concentrations, osmotic potential, and burial depths, compared with sensitive biotypes. This study elucidates the relationship between specific herbicide target enzyme mutations and weed germination fitness, and provides theoretical guidance for the control of resistant E. phyllopogon in the field. • Echinochloa phyllopogon exhibits varying levels of resistance to ALS inhibitors by distinct mechanisms. • A dCAPS method was first established to detect the Pro-197-Thr and Trp-574-Leu mutations in the ALS gene of E. phyllopogon. • R NTSR and R 197 biotypes, derived from the same resistant E. phyllopogon population, exhibited significant germination fitness costs under some environmental conditions.