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It has long been known that a bacterial leaf blight-resistant line in rice obtained from a crossing using 'Asominori' as a resistant parent also has resistance to blast, but a blast resistance gene in 'Asominori' has not been investigated in detail. In the present study, a blast resistance gene in 'Asominori', tentatively named Pias(t), was revealed to be located within 162-kb region between DNA markers YX4-3 and NX4-1 on chromosome 4 and to be linked with an 'Asominori' allele of the bacterial leaf blight resistance gene Xal, tentatively named Xal-as(t). An 'Asominori' allele of Pias(t) was found to be dominant and difference of disease severity between lines having the 'Asominori' allele of Pias(t) and those without it was 1.2 in disease index from 0 to 10. Pias{t) was also closely linked with the Ph gene controlling phenol reaction, suggesting the possibility of successful selection of blast resistance using the phenol reaction. Since blast-resistant com-mercial cultivars have been developed using 'Asominori' as a parent, Pias(t) is considered to be a useful gene in rice breeding for blast resistance. [ABSTRACT FROM AUTHOR]

To identify quantitative trait loci (QTLs) associated with the primary target traits for selection in practical rice breeding programs, backcross inbred lines (BILs) derived from crosses between temperate japónica rice cultivars Nipponbare and Koshihikari were evaluated for 50 agronomic traits at six experimental fields lo-cated throughout Japan. Thirty-three of the 50 traits were significantly correlated with heading date. Using a linkage map including 647 single-nucleotide polymorphisms (SNPs), a total of 122 QTLs for 38 traits were mapped on all rice chromosomes except chromosomes 5 and 9. Fifty-eight of the 122 QTLs were detected near the heading date QTLs Hdl6 and Hdl7 and the remaining 64 QTLs were found in other chromosome regions. QTL analysis of 51 BILs having homozygous for the Koshihikari chromosome segments around Hdl6 and Hdl7 allowed us to detect 40 QTLs associated with 27 traits; 23 of these QTLs had not been de-tected in the original analysis. Among the 97 QTLs for the 30 traits measured in multiple environments, the genotype-by-environment interaction was significant for 44 QTLs and not significant for 53 QTLs. These re-sults led us to propose a new selection strategy to improve agronomic performance in temperate japónica rice cultivars. [ABSTRACT FROM AUTHOR]

Quantitative trait loci (QTLs) for low cadmium concentration in brown rice were analyzed in 2008 and 2009 using 126 RIL (F6 and F7 plants) grown in a paddy field with high Cd concentration, which were derived from a cross between a high yielding Japanese rice cultivar 'Fukuhibiki' and an African upland rice cultivar 'LAC23' with the lowest cadmium concentration in rice grains. Totally two QTLs controlling low cadmium concentration in grains were identified in both 2008 and 2009, i.e., one on chromosome 3 (qLCdG3) and one on chromosome 11 (qLCdG11), which had opposite additive effects. In qLCdG11, 'LAC23' alleles had the effect of reducing cadmium concentration, but qLCdG3 had the opposite effect. The explained phenotypic variances of qLCdG11 were 9.4% in 2008 and 12.9% in 2009, and those of qLCdG3 were 13.9% in 2008 and 8.3% in 2009. Cadmium concentrations in brown rice showed positive correlations with grain length and grain weight. QTLs for grain length and grain weight were detected on chromosomes 3 and 11, but their positions differed from those for cadmium concentrations. These results suggest a possibility of successful marker-assisted selection of low cadmium trait derived from 'LAC23'. [ABSTRACT FROM AUTHOR]

Using 77 single-nucleotide polymorphic (SNP) markers and dot-blot analysis, we examined 218 rice cultivars, respectively occupying 99% and 92% of the planted areas of non-glutinous and glutinous rice for three consecutive years from 2003 to 2005 in Japan. Among them, 205 cultivars were identified at one time by the genotypes of 18 markers, but 13 cultivars belonged to six groups in which cultivars were indistinguishable from each other. The 205 cultivars were individually distinguished from the others using combinations of up to six markers. This result was considered to be useful for the identification of Japanese commercial rice cultivars, monitoring the contamination of rice with other cultivars, and rice breeding using these cultivars. [ABSTRACT FROM AUTHOR]