QTL Mapping of Cold Tolerance at the Seedling Stage using an Introgression Lines Derived from an Intersubspecific Cross in Rice

Abstract

Low-temperature stress is an important factor controlling the growth and development of rice (Oryza sativa L.) in temperate region. In this study, a molecular linkage map consisting of 136 SSR markers was employed to identify QTL associated with cold tolerance at the seedling stage. Leaf discoloration and SPAD value (chlorophyll content) of 80 recombinant inbred lines (RILs) from an intersubspecific cross between Milyang23 (O. sativa ssp. Indica) and Hapcheonaengmi3, a japonica weedy rice were evaluated. Rice plants were grown in a growth chamber for 15 days under low-temperature (13/20°C day/night) and control condition (25/20°C day/night). The degree of leaf discoloration was highly significantly correlated with the SPAD value in the low-temperature plot (r = -0.708, P < 0.0001). A total of four QTLs for SPAD were identified that explained phenotypic variance ranging from 5.4 to 16.0%. QTLs detected under the control condition were located on chromosome 2 and 5. Further, two QTLs inherited from Hapcheonawngmi3 that were found associated to an increased SPAD values were identified on chromosome 1 and 4. To delimit the position of qSPA-4, substitution mapping was performed which enabled its location in 810 kb region flanked by RM16333 and RM16368. The results indicated that Hapcheonaengmi3 contains QTL alleles that are likely to improve cold tolerance in Indica rice.