GENETIC PARAMETERS, PHYSIOLOGICAL AND MOLECULAR ANALYSIS OF ROOT AND SHOOT TRAITS RELATED TO DROUGHT TOLERANCE IN RICE (Oryza sativa L.)
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Date
2011-07-17
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University of Agricultural Sciences GKVK, Bangalore
Abstract
Rice (Oryza sativa (L.)) is the most important stable food crop for over half of the world’s population and it has renowned relationship with the humans since ages. Drought is the major constraint for rice production throughout world. Several physiological and morphological characters contributing resistance to drought in rice have been identified. Among all those, most studied and believed are root related attributes. Series of studies with OryzaSNP rice panel revealed significant genotypic difference for deep root growth. Based on deep root growth and water uptake characters, Dular and N22 were identified as the genotypes having better drought avoidance mechanism. Genetic variability study demonstrated higher PCV, GCV, heritability and genetic advance as per cent of mean for most of the characters. Correlation studies indicated highly significant and positive correlation of deep root growth with water uptake and grain yield. The inter-cluster distance was not consistent with the geographic distribution of varieties. The varieties belonging to diverse ecological regions clustered together whereas, genotypes of the same region have entered widely into separate groups. Top performing breeding lines identified under IRRI-India network trials such as ARB 3, ARB 4, DGI 307, IR 74371-54-1-1, IR 52561-UBN-1-1-2, IR 74908-80-B-3-3 have more water up taking capacity during drought stress period. Among the donors and parents, Azucena, Brown Gora, IRAT 109, Vandana and Budda recorded significantly higher water uptake. The greater drought resistance of breeding lines and donors over others was explained by the differences in real time water uptake rates and root growth. A study using IR 64 x Adeysel NILs demonstrated that the difference in rice root architecture is essential to bring about significant yield advantage in drought stress environments. The results of gene expression using IR 64 x Adeysel NILs revealed increased activity of LEA genes in top roots than deep roots under drought stress condition. Their up-regulation in both tolerant and susceptible genotypes indicated that the upregulation per se is not related to drought tolerance.
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