Creation and identification of peanut germplasm tolerant to triazolopyrimidine herbicides

Abstract

<p id="C3">At present, the germplasm resources of herbicide-tolerant peanut (<italic>Arachis hypogaea</italic>) are scarce, which restrict the diversification of peanut-based cropping system. To create peanut germplasm with tolerance to different herbicides, a mutant population consisting of more than 55,000 peanut lines were generated by ethylmethanesulfonate mutagenesis. We screened this population with a variety of different herbicides to obtain multiple mutants with tolerance to different herbicides. One of these lines displayed strong tolerance to florasulam and flumetsulam in the experiments with foliar herbicide spraying under field conditions as well as in various laboratory evaluation for the herbicide tolerance, while the herbicide-tolerant trait did not have adverse effects on peanut yield and quality. To determine whether this trait was associated with a target-site-based resistance to the herbicides, we compared gene sequences and relative expression levels of these two acetohydroxyacid synthases (AHASs) as the herbicide target enzymes between the mutant and wild type. Molecular cloning and sequence analysis revealed that peanut chromosome A10 and B10 each contained a gene, named as <italic>AhAHAS1a </italic>and <italic>AhAHAS1b</italic>, which were highly similar to <italic>Arabidopsis AHAS</italic>. Peanut chromosome A08 and B08 also each carried an <italic>AHAS</italic> gene, named as <italic>AhAHAS2a </italic>and <italic>AhAHAS2b</italic>, respectively. However, compared with the wild type, the genes in the mutants had no nucleotide substitutions that could alter the amino acid sequences. Furthermore, it was evident that there was no significant difference in the relative expression levels of <italic>AhAHAS</italic> genes between the mutant and wild type. In summary, these results indicate that the herbicide tolerance of the mutant might be caused by non-target-site-based resistance mechanism.