GENETIC MAPPING OF QTLs, CONTROLLING SHOOT FRESH AND DRY WEIGHT UNDER SALT STRESS IN RICE (ORYZA SATIVA L.) CROSS BETWEEN Co39 x MOROBEREKAN

A mapping population of 120 recombinant inbred lines (RILs) derived from the cross between Co39 (lowland, Indica) and Moroberekan (upland, Japonica) rice (Oryza sativa L.) cultivars was used to map QTLs associated with shoot growth traits under salinity on all chromosomes of rice. The dilution of salt concentration in shoot tissues by higher vegetative growth is an established mechanism of salt tolerance in plants. The fresh weight of shoots was recorded after 42 days of growth at 100 mol m(-3) NaCl + 5.0 mol m(-3) CaCl(2) in nutrient solution in a flood bench system. We also determined shoot dry weight and shoot fresh/dry weight ratio traits from the above data. A total of 7 QTLs for 3 shoot growth traits were detected on chromosomes -1, 2 and 6 in this study. Out of 4 QTLs for shoot fresh/dry weight ratio, 2 were located on chromosome -1 and one on each of chromosome -2 and 6, respectively. These QTLs explained 5.52-26.13% of the total phenotypic variation for shoot fresh/dry weight ratio trait. From 2 QTLs for shoot fresh weight one was found on each of chromosome -1 and 2 and the phenotypic variation explained by these QTLs was 9.89-13.17%. Whereas a single QTL for shoot dry weight was positioned on chromosome -2, in this study and explained 10.07% of the total phenotypic variation. Detection of QTLs for shoot growth traits at different chromosomes indicated that this character is controlled by multiple loci.