Plant Breeding Institute, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan
A mutant with a reduced culm number was found in the progenies of AC-11
(strain regenerated from A-5 Akamuro by anther culture) irradiated by gamma
rays. In the F\2\ population of its cross with the original strain, A-5
Akamuro, it was demonstrated that a single recessive gene, rcn, was
responsible for both the reduced culm number and dwarfness under field
conditions. Linkage analysis demonstrated that rcn was linked with the genes
belonging to the first linkage group such as wx (glutinous endosperm) and C
(chromogen for anthocyanin). The order of gene loci was obtained as follows:
The mutant gene, rcn, was epistatic to the dwarfing genes, d-2 (ebisu
dwarf), d\3\, d\4\, d\5\ (bunketsu waito or tillering dwarf). d-6 (ebisumochi
dwarf), and d-10 (toyohikari-bunwai tillering dwarf). The mutant plants
showed a perfect seed set and differed from similar mutants showing complete
or high sterilities which had been induced by gamma irradiation (Futsuhara
and Yamaguchi 1963).
The expression of reduced culm number and dwarfism trait was affected by temperature conditions. Although the mutant produced only one or two tillers under field conditions, its growth was nearly normal when grown in a vinyl-house. When irrigated with cool running water during the growing period, the tillering and growth of the mutant were much suppressed and the reduced culm number and dwarfism were expressed more clearly. This mutant would be useful in physiological and nutritional studies as an indicative material.
References
Futsuhara, Y. and H. Yamaguchi, 1963. A radiation-induced mutant of less tillering in rice. Jpn. J. Breed. 13: 183-185.