Inheritance of Cool Tolerance at the Booting Stage of Rice Cultivars in Hokkaido

Abstract

The analysis of segregation for cool tolerance at the booting stage I was conducted using F₂ populations derived from a half diallel cross among seven rice cultivars ; Hayayuki (cool tolerance:highly tolerant), Sorachi (tolerant), Hayakogane (tolerant), Ishikari (moderately tolerant), Yukara (intermediate), Norin 20 (moderately sensitive) and Toyohlkari (sensitive). 10reover, F3 progenies between Hayayuki and Norin 20 were also analyzed. Cool lvater irrigation method lvas applied to evaluate the degree of cool tolerance. The results of F₂ analysis indicated that 1) the difference in cool tolerance between Hayayuki and the other four cultivars, Sorach.i, Hayakogane. Ishikari and Yukara, was due to the difference in one dominant gene, 2) of these four cultivars orLly Hayakogane has a multiple allele to the incomplete, dominant gene harboured by the other three cultivars, 3) Norin 20 and Toyohikari do not harbour any major genes for cool tolerance.