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Information on the genetics of fertility restoration facilitates breeding and/or selection of restorer lines used in hybrid breeding program in a cytoplasmic male sterility (CMS) system. Inheritance of fertility restoration of WA type CMS in rice, (Oryza sativa L.) was studied utilizing IR58025A, IR62829A and IR68899A CMS lines and three restorers viz., Amol-2, IR50 and Poya. The F1s showed pollen and spikelet fertility similar to the restorer parents, indicating that restoration ability were dominant and the cytoplasmic-genetic sterility system of CMS lines were sporophytic in nature. Evaluation of fertility in F2 populations and testcross progenies (BC1) revealed that fertility restoration in Amol-2 and IR50 were controlled by two major dominant genes whereas, it was controlled by one dominant gene in Poya. Segregation for spikelet fertility in F2 and backcross generation conformed to the results on pollen fertility. Analysis of line x tester indicated predominance of non-additive genetic variance. It suggested greater importance of non-additive gene action in pollen and spikelet fertility expression and indicated very good prospect for the exploitation of non-additive genetic variation for pollen and spikelet fertility through hybrid breeding.

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Present study aimed to assess the relationship between grain yield and its components in 116 rice genotypes in F₂ generations obtained from crosses between Tarom-Jelodar and 229R cultivars. Correlation analysis showed that the number of panicle per plant (0.758), the number of filled grains per panicle (0.604), the 100 grains weight (0.401) and grain width (0.234) had significant positive relationships with grain yield. Also, between grain yield and number of nonfilled grain per panicle (-0.438) a significant negative correlation was existed. Analysis with stepwise regression five characters including: the number of panicle per plant, the number of filled grains per panicle, grain length, the number of non-filled grain per panicle and grain width justified 85% of the changes in grain yield in the model. Path analysis showed that the number of panicle per plant showed greatest positive effects (0.683) on grain yield. The data obtained in current study showed that the number of panicle, the number of filled grain and 100 grain weight can be considered as selection criteria to improve grain yield for rice breeding purposes.