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While mutagenesis breeding has been widely applied in major crops, its implementation in tropical horticultural species remains limited. In this study, we established a pingyangmycin-induced mutagenesis system using in vitro –cultured embryogenic callus of litchi. Treatment with gradient concentrations of pingyangmycin (0–40 mg/L) revealed an inverse relationship between chemical dosage and cell viability, with somatic embryogenesis completely inhibited at 40 mg/L. Whole-genome resequencing of treated callus identified 307,629 high quality somatic mutations (255,721 SNVs and 51,908 indels), with the 20 mg/L treatment group exhibiting the highest number of mutations. Further resequencing of 40 regenerated mutant lines from the cultivars ‘Feizixiao’ and ‘Lingnan15’ revealed 1,703,663 and 1,281,489 somatic variants, respectively, corresponding to mutation frequencies of 1.8×10 -4 per site and 1.4×10 -4 per site, both markedly exceeding typical EMS-induced rates in crops. Transition mutations predominated, accounting for 77% of total single-nucleotide substitutions. Short indels (3 bp) comprised over 70% of all insertion–deletion events, indicating pingyangmycin’s propensity to induce base substitutions and small indels via oxidative and double-strand break repair pathways. The regenerated mutant plants exhibited substantial leaf morphological variation, confirming effective mutagenic diversification. Collectively, this study provides the first evidence of pingyangmycin’s mutagenic efficacy in litchi, establishes a reliable system for mutant library construction, and delivers valuable genetic resources for functional genomics and molecular breeding applications.
Wang et al. (Fri,) studied this question.