Generation of gamma irradiation-induced mutant lines of the miniature tomato (Solanum lycopersicum L.) cultivar 'Micro-Tom'

One direct way to identify a gene and its function is a forward genetic approach based on mutation analyses. To accumulate genetic resources for breeding and functional genomics in the tomato, we generated 6,347 lines of an M-2 population with 300 Gy of gamma-ray irradiation in the inbred miniature dwarf variety 'Micro-Tom.' In total, 6,301 M-2 lines were screened based on morphological alteration and brix-aberration, and 237 lines were selected as mutant candidates at the first screening. Subsequent screening of the self-fertilized M-3 and M-4 progeny yielded 24 lines of morphological mutants and 11 lines of aberrant brix mutants. Segregation data suggested that most of the mutant lines had single recessive mutations, with the exception of two lines. The chlorophyll mutation ratio in germinated M-2 seedlings was 0.37% and the actual mutant frequency was 0.5%. The selected mutant lines exhibited a wide range of mutations, including whole plant properties with a severe phenotype, which allowed for more efficient screening of knockout mutants. Three characterized mutants, pale leaf, pink, and short root are also described.