Mohan Raju, B.SHASHIDHARA, K. N.2017-06-192017-06-192009-07-15Th-9331http://krishikosh.egranth.ac.in/handle/1/5810021791Among the several traits associated with drought tolerance, roots, water use efficiency and intrinsic tolerance at cellular level found to have some practical relevance under water limited conditions. Hence in the present study, one hundred and twenty lines of sunflower comprising parents and inbreds were evaluated in root structures for some of the relevant physiological traits associated with drought tolerance. Accordingly, a wide and significant genetic variability was found in several traits such as total leaf area, specific leaf area, root length, root volume, root dry weight, total dry matter and water use efficiency measured through carbon isotope discrimination approach. Existence of such a wide genetic variability in sunflower lines enabled to identify highly contrasting lines for roots, WUE and TDM and accordingly, a good number of lines with different drought tolerance traits have been identified. In order to check the consistency of traits and to test the relevance of roots under water limited condition, a subset of sunflower lines from contrasting groups were again evaluated in root structures by imposing moisture stress during active vegetative phase. The results of the study revealed that, even with a small subset of sunflower lines, a significant genetic variability in several of the physiological traits associated with drought tolerance was found both under control and stress condition to indicate that the material is diverse. A strong and significant correlation was also found for various traits such as total leaf area, root dry weight, TDM and ∆13C between 1st and 2nd experiment to indicate that the traits are consistent and heritable. Further, the high root types performed well over low root types under moisture stress condition to indicate that roots are important for imparting drought tolerance in sunflower. Overall, the existence of wide genetic variability and presence trait donor parents in sunflower will certainly help in sunflower improvement programme.ennullThesis