Investigation of Rice Genotypes Response to Reduced Irrigation Using Grain Yield and some Associate Characterize

In order to evaluation of rice genotypes response to drought stress and identify those tolerant and susceptible to this stress, the number of fifteen rice genotypes were investigated in completely randomized block design in thrice replicates under nonstressed (flooded, waterlogged) and late-season drought stress in agronomical year 2010 in research farm of university of Gonbad Kavous. Results of variance analysis showed that genotypes vary significantly in all studied traits under both environmental conditions so that landrace cultivars showed better drought stress responses. Mean separation analysis showed that under flooded condition, highest yield mean was related to Domsiah followed by Sorkho and Gardeh genotypes respectively and under drought stress, the genotypes Gardeh, Sang jo and IR83752-B-B123 respectively showed the highest yield. Stepwise regression analysis showed that under flooded and stressed conditions, 100 kernel weight and number of filled grains accounted for 79.6 and78.3% of grain yield variations as a the most important agronomical traits in selecting higher yield cultivars under flooded and drought stresses. In the present research, Given to biplot analysis and indices correlation, it was found that stress tolerance indices, geometrical mean, yield mean and harmonic mean indices were introduced as best criteria to select productive cultivars under both stressed and non-stressed conditions. Based on abovementioned indices and biplot graphs, the cultivars Gardeh, Sorkho, Sangjo, IR83752-B-B123, TaromAmiri and local Tarom were yield productive and drought stress tolerant whereasgenotypes of Shahpasand, Brsbonanc and Graldo were less productive and drought susceptible among others.