IDENTIFICATION OF QTL FOR COLD TOLERANCE IN THE GERMPLASM OF RICE (Oryza sativa L.)

Rice (Oryza sativa L.) is a major source of carbohydrate and staple food of more than 62% people in the world and biotic and abiotic stresses are the key limiting factors affecting rice production significantly. Approximately 45% of the global production of rice is lost annually owing to the damage caused by abiotic stresses, of which a significant share is attributed to the cold stress. Rice is affected by varying degree of low temperature like cool, chilling and freezing. To encounter the problem of yield loss due to low temperature, there have been various tactics in plant breeding. These tactics can be grouped into conventional approaches viz. bulk selection, mass selection, pedigree selection, pure line selection, hybridisation, back cross, transgressive breeding etc., and molecular approaches viz. induced mutation, cloning, tissue and cell culture, genetic engineering, MAS (marker assisted selection) etc. In this study to overcome the cold stress problem in rice crop, QTL approach was used, which is a part of MAS, using SSR molecular markers. A total 52 genotypes were used in this study for the identification of QTL conferring cold stress tolerance in germination and seedling stage of rice. A two directional approach which includes morphological assessment as well as genetic analysis, was used for the confirmation of cold tolerance in studied rice germplasm. For the morphological approach three different parameters viz., germination per cent, seedling height and seedling colour after cold treatment were used. While in genetic analysis confirmation with the resistant genotype was done. For the polymorphic survey a total of 52 SSR markers were used. The study showed that according to the morphological assessment there were total 30 resistant genotypes and 22 susceptible genotypes with varying degree of resistance and susceptibility. After genetic analysis 11 genotypes confirmed the presence of QTL for cold tolerance, among them BR-11 was the best genotype which showed the presence of 5 QTLs on five different chromosome. Among the selected 54 SSR markers, 25 SSR markers showed the strong association with cold tolerance in rice germplasm. Rice genotype BR-11 is recommended for an improvement programme as donor parent for cold tolerance.