Yoshihiro Sunohara

Variation in heading date conceals quantitative trait loci for other traits of importance in breeding selection of rice

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 japonica rice cultivars Nipponbare and Koshihikari were evaluated for 50 agronomic traits at six experimental fields located 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 Hd16 and Hd17 and the remaining 64 QTLs were found in other chromosome regions. QTL analysis of 51 BILs having homozygous for the Koshihikari chromosome segments around Hd16 and Hd17 allowed us to detect 40 QTLs associated with 27 traits; 23 of these QTLs had not been detected 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 results led us to propose a new selection strategy to improve agronomic performance in temperate japonica rice cultivars.

Yield and Lodging Resistance of 'Tachiayaka', a Novel Rice Cultivar with Short Panicles for Whole-Crop Silage

Abstract Abstract: ‘Tachiayaka’ is a novel cultivar of rice (Oryza sativa L.) with short panicles that is suitable for use in whole-crop silage. It was selected from bulked progeny obtained from two backcrosses of ‘Hoshiaoba’ to F1 plants of ‘Chugoku 146’ (‘Hoshiaoba’) × ‘Gokutansui (00kosen11)’. The unhulled rice yield of ‘Tachiayaka’ was comparable to that of ‘Tachisuzuka’, a short-panicle cultivar with high digestibility in cattle, in multi-location trials over a wide area spanning the Hokuriku to Chugoku regions in Japan. The whole-crop yield and the maturity of ‘Tachiayaka’ were comparable to those of ‘Hoshiaoba’. These findings indicated the suitability of ‘Tachiayaka’ for cultivation across a wide area of Japan. The characters associated with lodging resistance in ‘Tachiayaka’, including lodging index, were superior to those of ‘Hoshiaoba’. The high lodging resistance of ‘Tachiayaka’ will enable its cultivation in regions where lodging occurs frequently.