Growth characters and genetic inheritance in tomato cv. 'First' mutant with short internodes induced by seed irradiation with ion beam

Tomato (Lycopersicon esculentum L.) cv.'First' mutants with short internodes grew vigorously. The number of leaves slightly increased and the shape of the leaves was similar to wild type. In inflorescence morphology, the number of flowers increased and the length of peduncle and pedicel were shorter. In fruit characteristics, weight per fruit, total yield, sugar and acid contents were similar to wild type. But a lot of malformed fruit set was observed in the mutant line, due to the number of locules and short length of the peduncle and pedicel. The segregation ratio of the short internodes character fitted 3:1 of normal: short, hence it was considered to be controlled by a single pair of recessive genes. Allelism with already known dwarf gene was examined by crossing with 'Ailsa Craig', which had a symbolized dwarf gene, br or bu. Thereby, it was revealed that bu and short internodes gene were in the same gene locus. This mutant line has no negative effect on plant growth and fruit yields, but was unsuitable for use as fresh fruit by reason of malformed fruits. These results indicated the possibility of breeding of a new cultivar with bu gene derived from 'First'. Since the mutant with short internodes is derived from 'First', which is already a commercial variety with excellent characteristics, raising a new commercial variety with short internodes trait may not take a long time.