Mapping of QTLs for low temperature response in seedlings of rice (Oryza sativa L.)

A bioassay condition was developed to evaluate the low temperature response of rice (Oryza sativa L.) seedlings. Under this condition, an indica cultivar ‘Hokuriku 142’ did not survive, while a japonica cultivar ‘Hyogo-Kitanishiki’ showed 100% survival. A cross was made between the two cultivars to obtain F2 and F3 progenies. A frame map with 61 RFLP markers was constructed using 69 F2s, in which the segregation of all the markers was normal. Mean responses to the low temperature treatment of individual F2s were scored based on a 1–5 scale rating using F3s. A normal distribution was obtained showing that the low temperature response at the seedling stage was controlled by polygenes. Thirteen QTLs associated with the low temperature response were detected on the rice chromosomes 1, 3, 9 and 11 by the single point analysis. All QTLs except for 2 on chromosome 9 were with the effect in the same directions to those expected from the parental responses. The interval analysis revealed four QTLs on chromosomes 1, 3 and 11. The QTL-locating chromosomes 3, 9 and 11 show synteny with chromosome 5 of wheat and 7 (5H) of barley carrying genes for freezing tolerance.