Identification of quantitative trait loci for breaking and bending types lodging resistance in rice, using recombinant inbred lines derived from Koshihikari and a strong culm variety, Leaf Star

To develop rice varieties with increased biomass and grain yield, enhancing culm strength for superior lodging resistance is an essential trait. Leaf Star developed from a cross between Koshihikari and Chugoku 117 has a high bending stress despite its reduced lignin concentration owing to its high densities of hemicellulose, cellulose and low lignin density in the culm compared to Koshihikari, which shows superior resistance to lodging due to its combination of culm thickness and culm stiffness. However, the quantitative trait loci (QTLs) associated with these strong culm traits remain to be identified. Using 94 recombinant inbred lines (RILs) derived from a cross between Leaf Star and Koshihikari, a total of 12 QTLs on chromosome 1, 2, 3, 5, 10 and 11 were detected for breaking-type lodging resistance in F 7 and F 8 RILs. Further, a set of 12 QTLs affecting bending-type lodging resistance was detected in F 7 and F 8 on chr. 2, 3, 5, 10 and 11. QTLs for Section Modulus and Secondary Moment of Inertia on chr. 2 and 3 overlapped with QTLs associated with SCM3 on chr. 3 and SCM4 on chr. 2 from Chugoku 117 and Koshihikari. QTLs for starch and cell wall components such as cellulose and hemicellulose were detected on chr. 5 with Leaf Star allele’s contributions. These findings suggest that the detected QTLs contribute to strengthening the cell wall and play a key role in the mechanical strength of the culm, which contributes to lodging resistance.