Temperature Effect on Yield and Yield Components of Different Rice Cultivars in Flowering Stage

In order to study the effect of cold stress in flowering stage on yield and yield components of different rice cultivars, an experiment was performed as split plot factorial based on completely randomized design (CRD) in greenhouse of deputy of rice research institute of Iran (Amol) in 2010, in three repetitions. Treatment included 5 varieties as main factors that included cultivars of shirudi, fajr, local tarom, hybrid, and line 843. Two levels of temperatures T-1 (13 degrees C, stress temperature) and T-2 (32 degrees C, normal temperature, control) along with flowering stage were selected as two subfactors. Three seedlings were planted in each plot. The cold stress was done in flowering stage with holding pots at 13 degrees C for 15 days. Results showed that low temperature had significant effect in level of 1 percent on all characters, such as the number of panicles, the length of panicle, and the number of full, empty, and total grains; as a result, yield had caused significant reduction. Interaction between temperature and varieties showed that most tolerant variety in relation to temperature stress along with least percentage yield (19%) is shirudi variety and the most sensitive one with most percentage of yield decrease (29%) was local tarom variety.