Mapping of Quantitative Trait Loci for Cold Tolerance in Weedy Rice

Abstract

A quantitative trait locus (QTL) analysis was carried out with a recombinant inbred line (RIL) population to identify the chromosomal regions responsible for cold tolerance of rice (Oryza sativa L.). The RIL population, consisting of 80 lines, was developed from a cross between the indica cultivar, Milyang 23 and the japonica weedy rice, Hapcheonaengmi 3. The population was genotyped with 2 morphological and 132 DNA markers, providing an average interval size of 11.3 cM, and was also evaluated for traits related to agricultural performance in cold water and in control plots. The RILs showed delayed heading and reduced culm length in the cold water plot and the differences in heading date and culm length between two plots were statistically significant. Cold tolerance was measured as days to heading, culm length, spikelet fertility, leaf discoloration, and panicle exsertion in the cold water plot, and difference in days to heading and the reduction ratio of culm length between two plots. A total of 14 QTLs for 7 traits were identified using single point and composite interval analysis. The number of QTLs per trait ranged from one to three. Phenotypic variation associated with each QTL ranged from 5.8 to 32.8%. No digenic interaction was detected. Several QTLs associated with cold tolerance were clustered in a few chromosomal blocks. For 11 (78.6%) of the QTLs identified in this study, the Hapcheonaengmi 3-derived alleles contributed desirable effects and favorable alleles were detected for difference in days to heading, spikelet fertility, panicle exsertion and leaf discoloration. From this study, it can be concluded that weedy rice is useful as a source of valuable alleles for breeding cold tolerance in rice.