Genetic analysis of genetic basis of a physiological disorder “straighthead” in rice (Oryza sativa L.)

Straighthead is a physiological disorder in rice that causes yield losses and is a serious threat to rice production worldwide. Identification of QTL conferring resistance will help develop resistant cultivars for straighthead control. We conducted linkage mapping to identify QTL involved with straighthead. The study was based on a F₂ population developed from a cross between ‘Zhe733(resistant)/R312(susceptible)’. Using phenotypic data of F₂ plants and their F_2:3 families, two major QTL, qSTH-2 and qSTH-8, were identified using bulked segregant analysis, explaining 11.1 and 28.1 % of the phenotypic variation on chromosome 2 and 8, respectively. The qSTH-2 for straighthead resistance was identified by linkage mapping. qSTH-2 was situated near a QTL “AsS” responsible for arsenic accumulation. Straighthead is frequently observed on land where As has accumulated. The result suggests a kind of internal connection between qSTH-2 and AsS. Additionally, the QTL qSTH-8 was located close to HD5 related with heading date. The close location may be associated with the observation of early heading among straighthead resistant varieties. These findings should be useful for further genetic study of straighthead.