Comparison of Mutations Induced by Different Doses of Fast-Neutron Irradiation in the M 1 Generation of Sorghum ( Sorghum bicolor ).

Sorghum is an important C 4 crop with various food and nonfood uses. Although improvements through hybridization and selection have been exploited, the introduction of genetic variation and the development of new genotypes in sorghum are still limited. Fast-neutron (FN) mutagenesis is a very effective method for gene functional studies and to create genetic variability. However, the full spectrum of FN-induced mutations in sorghum is poorly understood. To address this, we generated an FN-induced mutant population from the inbred line 'BTx623' and sequenced 40 M 1 seedlings to evaluate the mutagenic effects of FNs on sorghum. The results show that each line had an average of 43.7 single-base substitutions (SBSs), 3.7 InDels and 35.15 structural variations (SVs). SBSs accounted for approximately 90.0% of the total number of small mutations. Among the eight treatment groups, FN irradiation at a dose of 19 Gy generated the highest number of mutations. The ratio of transition/transversion ranged from 1.77 to 2.21, and the G/C to A/T transition was the most common substitution in all mutant lines. The distributions of the identified SBSs and InDels were similar and uneven across the genome. An average of 3.63 genes were mutated in each mutant line, indicating that FN irradiation resulted in a suitable density of mutated genes, which can be advantageous for improving elite material for one specific or a few traits. These results provide a basis for the selection of the suitable dose of mutagen and new genetic resources for sorghum breeding.