Delimitation of the chromosomal region for a quantitative trait locus, qUVR- 10, conferring resistance to ultraviolet-B radiation in rice (Oryza sativa L.).

Wide variation in ultraviolet-B (UVB) resistance is observed among rice varieties. In a previous study, three quantitative trait loci (QTLs) controlling UVB resistance were detected by QTL analysis, using backcross inbred lines (BILs) derived from a cross between a japonica cultivar, 'Nipponbare', and an indica cultivar, 'Kasalath'. Among them, qUVR- 10, a QTL for UVB resistance on chromosome 10, showed the largest effect. Plants homozygous for the Nipponbare allele at qUVR- 10 were resistant to UVB, unlike those homozygous for the Kasalath allele. To determine more precisely the chromosomal location of qUVR- 10, we performed a linkage mapping of qUVR- 10 as a single Mendelian factor using advanced backcross progeny. Advanced progeny testing of F(4) families enabled us to determine the genotype classes of the qUVR- 10 locus with high reliability. As a result, qUVR- 10 was mapped between RFLP markers C60755S and C1757S, and co-segregated with C913A. In addition, a sequence showing high similarity to the Arabidopsis cyclobutane pyrimidine dimer (CPD) photolyase gene, which has been found to be involved in sensitivity to UV radiation in Arabidopsis and rice, was mapped in the candidate genomic region of qUVR- 10. This result suggests that the CPD photolyase gene is a positional candidate for qUVR- 10.