Phenotypic characterization of high temperature tolerant mutants of USDA110 generated by ion-beam irradiation

Takeda, Kiyoko; Tejima, Kohei*; Sato, Katsuya; Narumi, Issei; Yokoyama, Tadashi*

We have tried to improve high temperature tolerance of USDA110, which is a superior inoculant to soybean in temperate area, using ion beam breeding technology. Consequently, we have obtained 20 high-temperature tolerant mutants, which can survive at 43C for at least 7 days. In this report, we show phenotypic characteristics of 3 mutants (strains M4, M5 and M6) that exhibit relatively higher tolerance among the mutants obtained. The colony of M4, M5 and M6 was smooth with glossy pale pink color unlike wild type. There might be a link between high temperature tolerance and these phenotypic changes. Therefore, we intend to identify factors causing these changes. The generation time of high-temperature tolerant mutants at 30C was about 1.5 h shorter than that of wild type.