Molecular markers from QTLs fine mapped regions of the candidate genes calmodulin-binding transcription activator (CMTA) and integral membrane Duf6 domain containing protein are associated with seedling cold tolerance in rice (Oryza sativa L.)

Cold stress at the seedling stage is a major threat to rice production. Cold tolerance is controlled by complex genetic factors. We used an F7 recombinant inbred line (RIL) population of 123 individuals derived from the cross of a cold-tolerant japonica and a cold-sensitive indica cultivars, for QTL mapping. Phenotypic evaluation of the parents and RILs in an 18/8oC (day/night) cold-stress regime showed continuous variations for cold tolerance or sensitivity. Six QTLs for seedling cold tolerance were identified on chromosomes 1, 2, 4, 10, and 11 with percent phenotypic variation (R2) ranging from 6.1% to 16.5%. Three main-effect QTLs (qSCT1, qSCT4, and qSCT11) were detected in all cold-tolerant RILs which explained high sum of phenotypic variation (SPV) ranging from 27.1% to 50.6%. Two QTLs (qSCT1 and qSCT11) on chromosomes 1 and 11 were fine mapped. The marker In1-c3 from ORF LOC_Os01g69910 of the BAC clone B1455F06 encoding calmodulin-binding transcription activator (CAMTA) and another marker, In11-d1 from ORF LOC_Os11g37720 (Duf6 gene) of the BAC clone OSJNBa0029K08, co-segregated with seedling cold tolerance. These two InDel markers amplified 241-bp and 158-bp alleles, respectively, in cold-tolerant RILs, and in the cold-tolerant donor Jinbu, which were absent in cold-sensitive parent BR29 and cold-sensitive RILs.