GENETIC-ANALYSIS OF STUNTED GROWTH BY NUCLEAR-CYTOPLASMIC INTERACTIONIN INTERSPECIFIC HYBRIDS OF CAPSICUM BY USING RAPD MARKERS

When eight cultivars of Capsicum annuum were used as female parents in interspecific crosses with two accessions of C. chinense, dwarfism oc curred in hybrids originating from 10 out of 16 combinations, while hy brids of the remaining 6 combinations grew normally. In contrast, when C. chinense was used as female parent, all of the hybrids showed seve rely stunted growth as if affected by a virus. These results suggested that the stunted growth expressed in the cross of C. chinense x C. an nuum is caused by an interaction between nuclear gene(s) from C. annuu m and the cytoplasm of C. chinense. To examine the number of nuclear g ene(s) which cause(s) the stunted growth, we backcrossed F1 hybrids of C. annuum x C. chinense to C. chinense. About one-quarter of the prog eny in the backcrossed hybrids of C. chinense x (C. annuum x C. chinen se) showed the same stunted growth shown by the F1 hybrids of C. chine nse x C. annuum, suggesting that two complementary genes of C. annuum cause the stunted growth. However, the higher abortion rates of ovules and lower germination percentage of seeds in C. chinense x C. annuum than in the selfed C. chinense implied that the genetic ratio of the s tunted type would have been higher than that observed in the C. chinen se x (C. annuum x C. chinense) progeny. We then attempted a linkage an alysis between the stunted growth and randomly amplified polymorphic D NA (RAPD) of C. chinense x (C. annuum x C. chinense) progeny. A RAPD m arker that associated with 94% of the stunted plants but not with 94% of the normal one was identified. This confirmed that a single nuclear gene of C. annuum which is linked to the RAPD marker with a recombina tion value of 6% causes the stunted growth in an interaction with the cytoplasm of C. chinense.