Male Sterility of an -Mutant Induced by Tribenuron-Methyl Solution Correlated With the Decrease of AHAS Activity in L.

Tribenuron-methyl (TBM), an acetohydroxyacid synthase (AHAS)-inhibiting herbicide, can be used as an efficient chemical hybridization agent to induce male sterility for practical utilization of heterosis in rapeseed ( L.). Utilization of rapeseed mutants harboring herbicide-resistant AHAS alleles as the male parent can simplify the hybrid seed production protocol. Here we characterized a novel TBM-resistant mutant derived from an elite rapeseed variety, Zhongshuang No. 9 (), by ethyl methyl sulfonate mutagenesis. Comparative analysis of three genes (, and ) between the mutant and identified a C-to-T transition at 544 from the translation start site in in (This resistant allele is referred to as ), which resulted in a substitution of proline with serine at 182 in BnAHAS1. Both and plants could be induced complete male sterility under TBM treatment (with 0.10 and 20 mg⋅L of TBM, respectively). The relationship between TBM-induced male sterility () and the relative AHAS activity of inflorescences () could be described as a modified logistic function, = 100-/(1+) for the both genotypes, although the obtained constants , and were different in the functions of and . Transgenic plants expressing exhibited a higher TBM resistance of male reproductive organ than wild type, which confirmed that the Pro-182-Ser substitution in BnAHAS1 was responsible for higher TBM-resistance of male reproductive organs. Taken together, our findings provide a novel valuable rapeseed mutant for hybrid breeding by chemical hybridization agents and support the hypothesis that AHAS should be the target of the AHAS-inhibiting herbicide TBM when it is used as chemical hybridization agent in rapeseed.