Genetic Basis Of Cold Tolerance In Rice

Cold is one of the main abiotic constrains in rice production. Understanding the genetic mechanism of cold tolerance (CT) of rice is very important in developing CT rice cultivars. In this study, a DH population derived from a cross between a cold-tolerant japonica variety Duonianshengdao and a cold-sensitive indica cultivar Zhenshan97B was used to identify quantitative trait loci (QTL) conferring CT at four growth stages. The major results were as follow:1. A genetic linkage map was constructed based on the data of 146 loci assayed on the 192 individuals by Mapmaker analysis. The map covered a total of 1546.3cM with an average interval of 10.6cM between adjacent loci, and 44.5% of all the markers founded to be distorted segregation.2. The germinability was measured as the percentage of germination of treated seeds at 15℃ for 6d, and 10 QTL for low temperature germinability were detected with accumulated contribution of 59.76%. The indica parent Zhenshan97B was more cold tolerant than japonica parent Duonianshengdao at this stage, and most of the alleles which could increase CT came from Zhenshan97B. There were also 7 pairs of epistasis QTL affecting low temperature germinability accounted for 25.05% of the total phenotypic variance. Additive effect of the QTL played more important role in low temperature germination than epistasis effect.3. Used the survival percentage as evaluation index for cold tolerance at budding stage, fourteen additive QTL were detected under three replicated trials. There are a QTL located in marker interval RM499-RM84 on chromosome 1 had been detected at all three replications, and another QTL on chromosome 3 explained 20.21% of the total phenotypic variance. Twelve of the fourteen QTL were contributed by Duonianshengdao. In the three trials, 9, 10 and 5 pairs of epistatic interactions were detected, respectively, with the average accumulated R~2 about 30%. Additive effect contributed to budding cold tolerance greater than epistasis effect.4. By dynamically analyzing every two day's survival percentages and wilting degree of the parents and DH lines in five experiments with four different treatments, thirty six quantitative trait loci (QTL) for cold tolerance at seedling satge were mapped on ten of twelve rice chromosomes. There are...