Line (five) × tester (two) analysis was conducted to determine good parents and the nature of gene action governing yield and its component traits in rice. The line × testers showed significant differences for all traits except for number of spikelets per panicle and hundred grain weight. Parents with low × high general combining ability (GCA) effects resulted in heterotic hybrid combination like the IR62829A/IR57301-158-1R. A low × low GCA gave the best heterotic combination i.e. IR68888A/'Sepidroud'. The study showed GCA to only identify better parental lots and it will be unwise to discard the low GCA types. Predominance of dominance gene action for all the traits studied except for flag leaf width and number of spikelets per panicle suggests heterosis breeding must be strongly pursued for exploitation of the yield advantage over the inbred varieties.

No abstract

Because of waterlogged conditions in rice cultivation, much of the surface-broadcasted urea dissolves in paddy water and is unreachable to the rice crop for this reason. A field experiment was conducted to estimate the influence of urea fertilisation on yield and yield components of hybrid rice ‘Bahar 1’. Three doses (N0, N10, N20 kg N ha-1) of nitrogen from urea sources were foliar-sprayed once at active tillering and booting stages. Grain yield, the number of panicles per unit area, and the number of grains per panicle in the tillering stage of rice were significantly (p < 0.01) increased in a linear fashion when N rates increased from 0 to 20 kg ha-1. The rate of panicle fertility was negatively/positively influenced with increasing N rates in the tillering and booting stages, respectively, indicating the creation of more number of non/partial productive tillers per hill in the vegetative stage than in the reproductive stage. In line with panicle fertility (%), the grain yield was also significantly affected by N treatments with urea fertilisation in the booting stage. Maximum grain yield was obtained with the application of 20 kg N ha-1 at both the tillering and booting stages. Foliar spraying of urea at tillering (20 kg N ha-1) and booting (10 kg N ha-1) stages had a pronounced effect on achieving higher yields as compared to other combinations. The study suggests that foliar application of urea for hybrid rice cultivation might have a potential role in improving nitrogen use efficiency.