Atul KumarLingwan, Maneesh2018-04-172018-04-172016-06http://krishikosh.egranth.ac.in/handle/1/5810043732Rice (Oryza sativa L.) is a globally important cereal crop, and primary source of food. As the growth of word’s population is increasing, so more demand of rice will be required. There is a challenge to achieve more production of rice. Heat stress is major factor which greatly affects the growth, development and productivity of rice. To evaluate the morphological and biochemical response of rice genotypes under heat stress, a field experiment was conducted in Norman E. Bourlog Crop Research Centre, G.B. Pant University of Agriculture and Technology, Pantnagar during kharif season 2015 with 24 rice genotypes, namely- IET 23339, IET 23354, IET 23356,IET 23392, IET 23947, IET 23949, IET 23951, IET 23957, IET 23976 IET 23979, IET 23996, IET 24075, IET 24082, DRRH-106 ,DRRH-107 ,DRRH-108,Govind, NDR-97,PA6129, PHY-1,PHY-2 ,Sabagidhan, Tulasi, N22. These genotypes were transplanted into two blocks, one for control and another for imposing heat stress by a poly sheet tunnel supported by bamboo sticks. The heat stress treatment was given at the time of anthesis. A maximum and minimum temperature thermometer was fixed to record the daily maximum and minimum temperature inside the poly sheet tunnel. A number of parameters such as leaf length, width, leaf area, leaf dry weight, stem dry weight, panicle weight, total dry matter production, 1000-grain weight, grain yield, chlorophyll content, grain protein and amylose content were recorded in different rice genotypes. Heat stress reduced leaf area, stem dry weight at harvest, panicle dry weight, 1000-grain weight, and number of filled grain, grain yield, total dry matter production, chlorophyll content and amylose content of different rice genotypes. While heat stress increased stem dry weight per plant at flowering, total dry matter (leaf and stem) at flowering, and number of unfilled grains and protein content of different rice genotypes. Out of twenty four genotypes of rice, the rice genotypes namely DRRH107, DRRH-108, PA-6129, PHY-2 and N 22 performed better under heat stress treatment under the poly sheet tunnel in tiller numbers per plant, filled grains per panicle, fertility (%) and grain yield as compared to rest of different rice genotypes. These tolerance rice genotypes can further explored for the molecular mechanism, responsible for heat tolerance and better yield.ennullThesis