Colocalization of QTLs for hull-cracked rice and grain size in elite rice varieties in Japan.

The control of insects that consume cereal grains is important for the production and storage of grains. Hull-cracked rice, which has splits in the hull, becomes more susceptible to insects both in the paddy field and during storage. The development of varieties with a low frequency of hull-cracked rice is the most economical and effective strategy to avoid insect damage and the environmental risks from agricultural chemical entering rice grains. In this study, we identified that QTLs for the frequency of hull-cracked rice and for grain width are located on the same chromosome using recombinant inbred lines derived from a cross between the elite rice varieties in Hokkaido, Japan, which are from the same pedigree and are genetically closely related. These QTLs were detected close to different molecular markers, which were separated by 1,101,675 bp, on chromosome 5 in the reference Nipponbare genome. In addition, low coefficient values of the phenotype were found between hull-cracked rice and grain size. These results suggested that the ratio of hull-cracked rice is independent of grain size. Using these QTLs, new varieties with low hull-cracked rice could be developed regardless of grain size.