In vitro mutagenesis and directed screening for salt-tolerant mutants in peanut

To expand the salt-tolerant gene resources of peanut, we conducted in vitro mutagenesis with pingyangmycin (PYM) as the mutagen and directed screening with medium containing NaCl. After embryonic leaflets from mature peanut seeds (variety Huayu 22) were cultured on somatic embryogenesis-induction medium containing 4 mg/L PYM for 4 weeks, the surviving somatic embryos were sequentially transferred to a germination medium containing 15 and then 20 g/L NaCl. The 30 NaCl-tolerant plantlets obtained were grafted and transplanted in the field in 2011, and the mature seeds of 26 regenerated plants were harvested. In 2012, all seeds from each plant were sown in the field. The offspring (M2 generation) of 23 of 26 NaCl-tolerant, regenerated plants differed from their mutagenic parent in vigor, growth habit, flowering habit, pod shape, and seed coat color, and they also exhibited trait segregation from the same NaCl-tolerant, regenerated plant. In a germination test with a 0.7 % NaCl solution and the M3-generation seeds from 18 of the NaCl-tolerant, regenerated plants, the germination rate was substantially higher for the seeds from 6 plants than for seeds from the mutagenic parent (Huayu 22). To determine whether the changes in plant traits might be associated with gene mutations, DNA polymorphisms between the mutagenic parent and 19 M3 generation individuals from different NaCl-tolerant, regenerated plants were analyzed with 39 pairs of SSR primers, and all mutants differed from the mutagenic parent in >2 loci. The results indicate that the use of PYM-based mutagenesis in combination with directed in vitro screening with NaCl is effective for creating and identifying salt-tolerant mutants of peanut.