Induction of Extremely-early-heading Mutants in Wheat : Studies on the Utility of Artificial Mutations in Plant Breeding XVII.

Abstract

Release of early-maturing varieties which can be harvested before the onset of the rainy season is very important for wheat breeding in Japan. However, the efforts of breeders have not yet been rewarded due to the difficulty in procuring the early-heading genes required for the breeding of the desired early-maturing varieties. The present study was carried out to develop extremely-early-heading mutants and to examine why early-heading mutations are rare in wheat. Seeds of three early-, three intermediate- and three late-heading varieties were irradiated with 20-30kR gamma-rays and subjected to two experiments. In Exp. 1, the M₂ plants were grown in bulk and grouped according to the varieties and doses, then screened for early-heading variants. In Exp. 2, the M₂ plants were raised by the ear-to-row method for four of the nine varieties, then 1% selection in each of the early and late directions was made for each variety and dose. In both experiments, early-heading variants were selected in the M₃, and the M₄ progeny lines were examined to determine whether they were mutants while several agronomic characters including flowering time were analyzed.