Effects of source and sink limitation on yield and yield components of some rice cultivars

In order to determine the effect of source-sink limitation on yield and yield components of four rice cultivars, an experiment was conducted at Rice Research Institute of Iran, Deputy of Mazandaran (Amol) in 2003. The experiment was in factorial based on randomized completely block design with four replications. The studied factors were source-sink limitation in four levels (cutting of all leaves except flag leaf cutting of flag leaf cutting of 1/3 end of panicle control) and cultivars in four levels (Tarom Neda Shafagh Fajr). Some traits such as grain yield, harvest index, grain number per panicle, unfilled grain number per panicle, panicle length, panicle fertility and 1000 grain weight in different source-sink limitation treatments were investigated. Results showed that imposing of different source-sink limitation treatments had a positive effect on all mentioned traits. Interaction effect between cultivar and source-sink limitation was also significant. The control and cutting of 1/3 end of panicle treatments had the highest (5255.3 kgha-1) and the lowest (4055.1 kgha-1) grain yield, respectively. Among cultivars, Neda had the highest grain yield (5419.6 kgha-1). Cutting of 1/3 end of panicle and cutting of flag leaf treatments had the highest (88.55 %) and the lowest (76.4 %) panicle fertility, respectively. There were positive and significant correlations between grain yield and harvest index, panicle length and grain number per panicle, but 1000 grain weight had a negative correlation with grain yield that was not significant. Generally, results showed that cultivar Tarom had sink limitation and other cultivars (Neda, Shafagh and Fajr) had source limitation