Genetic studies on the interspecific cytoplasm substitution lines of japonica varieties of oryza sativa and oryza glaberrima
Euphytica 26(2): 451-463
ISSN/ISBN: 0014-2336 DOI: 10.1007/bf00027007
Interspecific cytoplasm substitution lines of O. sativa and O. glaberrima, i.e., (sativa)-glaberrima and (glaberrima)-sativa, were bred by means of successive backcrosses, using 3 Japonica varieties of O. sativa and 2 O. glaberrima strains. In all 6 substitution lines with the cytoplasm of O. glaberrima strains, fertility increased with succeeding backcrosses, and eventually completely fertile plants with characteristics of the parental japonica variety appeared. The O. glaberrima cytoplasm exerted no effect on the genome manifestation of these japonica varieties. Of the 5 substitution lines with the cytoplasm of each of the japonica varieties, 4 lines produced male sterile (M.S.) plants only in the backcross generations. In the remaining substitution line with the cytoplasm of the japonica variety Akebono, there was simultaneous segregation for male sterile (M.S.) and pollen fertile plants bearing indehiscent anthers (ID.M.F.) in the backcross generations. In the compulsively selfed progeny of ID.M.F. plants, pollen fertile plants with dehiscent anthers (D.M.F.) occurred with M.S. and ID.M.F. plants. Morphologically, these 3 types were supposed to have the same genetic background as the O. glaberrima parent. D.M.F. and ID.M.F. plants were homozygous and heterozygous for a dominant nuclear gene restoring pollen fertility, respectively, and the M.S. plants and the 2 O. glaberrima strains carried a recessive gene for pollen sterility in homozygous condition. The restorer gene was assumed to derive from the japonica variety Akebono. The expression of the restorer gene was of the sporophytic type. The pollen sterility of the substitution lines that possessed the cytoplasm of the japonica varieties was of cytoplasmon-genic nature.