Abstract
Hybrid rice parental lines with better combining abilities provide an efficient tool to increase rice production. In the current study, twenty hybrid combinations were generated from five aromatic cytoplasmic male sterile (CMS) lines and four restorer lines (three of them aromatic) using a line × tester mating design. The hybrids and their parental lines were evaluated under two water regimes: normal irrigation and water-stress. Ten yield-component traits were studied over a period of 2 years, and the significant differences between the parents and hybrids are reported in this investigation. Overall, all yield component traits were significantly affected by the water deficit and were governed by both additive and non-additive gene actions. More specifically, the grain yield (GY) was mainly controlled by non-additive gene action under both normal and water-stress conditions. The contribution of the additive variance (σ2 A) was more prominent in the genetic components of traits as compared to the dominance variance (σ2 D). The aromatic parental line CMS IR58025A and the restorer line PR2 were recorded as the best combiners for the GY and good combiners for many other characteristics under both growth conditions. The cross combinations Pusa12A/IR25571-31R and Pusa12A/Giza-Basmati-201 revealed significantly positive specific combining ability (SCA) effects for the GY under both normal and water-stress conditions. The inconsistent correlation between the general combining ability (GCA) and SCA manifested complex interactions among the positive and negative alleles of the genes controlling the yield traits. Generally, the findings of this investigation demonstrated the importance of the GCA and SCA for understanding the genetic components and gene actions of the yield characteristics in new aromatic hybrid rice parental lines. Therefore, we recommend considering these findings in the selection of elite parents for developing superior aromatic hybrid rice varieties under water-stress conditions.
Highlights
Rice is a prominent global crop that provides essential food for the majority of human beings
These yield characteristics included the day to maturity, plant height, panicle length, spikelets panicle−1 (SP), panicles plant−1 (PP), panicle weight (g; PW), filled grains panicle−1 (FGP), spikelet fertility (%; SF), 1000-grain weight (g; GW), and grain yield plant−1 (g; GY) according to [23]
Dendrogram Analysis: The cytoplasmic male sterile (CMS) and tester lines were clustered based on 10 agronomic traits using the UPGMA method of hierarchical clustering [24]
Summary
Rice is a prominent global crop that provides essential food for the majority of human beings. The wide adoption of semi-dwarf and early maturing Egyptian varieties expedited the rice yield per unit from 5.7 t/ha in the 1980s to the level of 9.52 t/ha in the 2000s [5] This increase in rice production still could not match the increasing rate of population with the decrease in water resources. The current investigation was conducted to assess the combining ability and gene action for yield-related traits in new aromatic CMS lines under both normal and water-stress conditions. This is useful for developing elite aromatic hybrid rice varieties
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