The impact of carbon-ion beam irradiation on the phenotypic and molecular variation of wheat

Heavy ion beam irradiation is a potent mutagenic technique for developing new germplasm resources and breeding novel plant varieties. However, the biological effects and molecular variations caused by different dosages of heavy ion beam irradiation in crops are still not well understood. In this study, we investigated the biological effects and molecular variations in the M1 generation of wheat, along with extensive phenotype screening in the M2 generation, to thoroughly assess the mutagenic impact of carbon-ion beam irradiation. Our findings indicate that radiation doses of 60–120 Gy significantly reduced seedling height and root length, with a 50% survival rate occurring at the dose of 87 Gy. We examined a total of 1840 M2 plants for phenotypic mutations and found a mean mutation frequency of 2.68%. Transcriptome sequencing revealed that irradiation induced single nucleotide polymorphisms (SNPs) and small insertions and deletions (indels), with transition/transversion ratios ranging from 1.96 to 2.03. Mutation hotspots were identified in the Chr1A, 3A, 6D, and 7D regions. Additionally, weighted gene co-expression network analysis (WGCNA) identified genes such as CAT, NPF, and BZIP which showed a high correlation with dosage response and are predominantly involved in starch and sucrose metabolism. Metabolome analysis at a radiation dose of 100 Gy revealed that the differential metabolites were predominantly involved in tryptophan metabolism. These pathways may play a crucial role in the response to radiation. This study provides valuable information and resources for mutation breeding in crops, enhancing our understanding of carbon-ion-beam-induced mutations in wheat.