Bains, GurdeepRawat, Pratibha2018-06-202018-06-202017-06http://krishikosh.egranth.ac.in/handle/1/5810054601Rice is a global food for more than 60% of the world’s population. It is very sensitive to environmental factors such as temperature, light, drought etc. during critical stages of growth, such as flowering and seed development. Low light stress is an important constraint for rice productivity in Southeast Asia. For physiological and biochemical characterization of rice genotypes for low light stress tolerance, a field experiment was conducted in Norman E. Bourlog crop research center, G. B. Pant University of Agriculture and Technology, Pantnagar during kharif season 2016 with different rice genotypes, namely, IET 24195, IET 24183, IET 24189, IET 24188, Vivekdhan 86, IET 24197, IET 24192, IET 25149, IET 25157, Shalimar Rice 3, IET 25144, IET 25154, IET 27P63, US-314, Tulasi and Swarnaprabha, respectively. These genotypes were transplanted in two blocks, one for control and another block for imposing low light stress by covering the block with 50 % shade net supported by bamboo sticks. Both the entry ends were open for sufficient ventilation. A number of parameters such as plant height, tiller number, leaf area, chlorophyll, protein, carbohydrate, amylose, phenol and Zinc content, grain yield, thousand grain weight and spikelet fertility, total dry matter, root length, root weight, stem weight, panicle number were recorded in different rice genotypes and it was found that except plant height and chlorophyll content, all the parameters reduced significantly under low light stress. The genotypic variations in these characteristics were also found. Some genotypes showed tolerance for low light stress and some were found to be susceptible. Finally the grain yield, harvest index, number of filled spikelet and percent spikelet fertility indicated that low light stress adversely affected these parameters. The low light stress tolerant genotypes performed better in terms of filled grain numbers and percent spikelet fertility per panicle, harvest index as compared to susceptible genotypes. In present study, US-314, IET 27P63, and Swarnaprabha were found to be tolerant. Low light stress effect on soil microbial community was also studied by molecular methods like RT PCR and DGGE and it was found that low light stress significantly reduced the soil microbial community as compared to control conditions.ennullThesis