Molecular Genetic Diversity and Combining Ability for Some Physiological and Agronomic Traits in Rice under Well-Watered and Water-Deficit Conditions

Abstract

Water deficit is a pivotal abiotic stress that detrimentally constrains rice growth and production. Thereupon, the development of high-yielding and drought-tolerant rice genotypes is imperative in order to sustain rice production and ensure global food security. The present study aimed to evaluate diverse exotic and local parental rice genotypes and their corresponding cross combinations under water-deficit versus well-watered conditions, determining general and specific combining ability effects, heterosis, and the gene action controlling important traits through half-diallel analysis. In addition, the research aimed to assess parental genetic distance (GD) employing simple sequence repeat (SSR) markers, and to determine its association with hybrid performance, heterosis, and specific combining ability (SCA) effects. Six diverse rice genotypes (exotic and local) and their 15 F1 hybrids were assessed for two years under water-deficit and well-watered conditions. The results revealed that water-deficit stress substantially declined days to heading, plant height, chlorophyll content, relative water content, grain yield, and yield attributes. Contrarily, leaf rolling and the sterility percentage were considerably increased compared to well-watered conditions. Genotypes differed significantly for all the studied characteristics under water-deficit and well-watered conditions. Both additive and non-additive gene actions were involved in governing the inheritance of all the studied traits; however, additive gene action was predominant for most traits. The parental genotypes P1 and P2 were identified as excellent combiners for earliness and the breeding of short stature genotypes. Moreover, P3, P4, and P6 were identified as excellent combiners to increase grain yield and its attributes under water-deficit conditions. The hybrid combinations; P1 × P4, P2 × P5, P3 × P4, and P4 × P6 were found to be good specific combiners for grain yield and its contributed traits under water-deficit conditions. The parental genetic distance (GD) ranged from 0.38 to 0.89, with an average of 0.70. It showed lower association with hybrid performance, heterosis, and combining ability effects for all the studied traits. Nevertheless, SCA revealed a significant association with hybrid performance and heterosis, which suggests that SCA is a good predictor for hybrid performance and heterosis under water-deficit conditions. Strong positive relationships were identified between grain yield and each of relative water content, chlorophyll content, number of panicles/plant, number of filled grains/panicle, and 1000-grain weight. This suggests that these traits could be exploited as important indirect selection criteria for improving rice grain yield under water-deficit conditions.

Genetic Behavior of Some Rice Root Characteristics, Yield and Yield Components as Affected by Water Deficit

“…The ANOVA for 12 traits in 8 × 8 half diallel set (Table 1) showed highly significant mean square estimates were recorded for genotypes, parents, crosses and the interaction among them for all root characteristics, yield and yield components under water deficit and normal conditions, except root/shoot ratio and 1000-grain weight under both conditions and leaf rolling under normal conditions which were insignificant. These results agree with those obtained by Saleem et al (2010), El-Hity et al, (2016, Daher (2018) and Sakran et al (2022). Results also revealed that variances due to the general combining ability (GCA) and the specific combining ability (SCA) were significant for all the studied traits, indicating the important of both additive and nonadditive gene action in the inheritance of all traits except root /shoot ratio and 1000-grain weight under both conditions and leaf rolling for (SCA) and (GCA) under both conditions and normal conditions, respectively.…”

Variable level of genetic dominance controls important agronomic traits in rice populations under water deficit condition

“…These findings were supported by several studies ( Ahmadikhah, 2018 ; Hossain et al, 2021 ; Kamara et al, 2017 ; Tiwari et al, 2019 ), wherein it has also been suggested that these aforementioned crosses could be used to explore the heterotic effects in hybrid rice breeding programs with water deficit conditions ( Concepcion et al, 2015 ; Guimarães, Stone & Silva, 2016 ; Hassan, 2017 ; Hastini et al, 2021 ; Potkile et al, 2018 ). Furthermore, significant heterosis percentages were recorded for these traits in studied crosses, which was corroborated by previous studies ( Gaballah et al, 2021 ; Ouyang, Li & Zhang, 2022 ; Sakran et al, 2022 ).…”

“…This juncture leads to the conclusion that these traits can be improved through conventional breeding methods and selection can be effective mostly in later generations, similar results were found by Abebe, Alamerew & Tulu (2019) and Farooq et al (2019) . High estimates of GS % expressed as mean percentages were found in all the studied traits in both crosses under both conditions, which were corroborated by the previous study ( Sakran et al, 2022 ). In addition, most of the studied traits had high estimates for h 2 b and therefore high GS, suggested that those traits are either simply inherited or governed by a few major genes, or that additive gene effects played important roles in the inheritance of these traits ( Ouyang, Li & Zhang, 2022 ).…”

Genetic Potential and Inheritance Patterns of Physiological, Agronomic and Quality Traits in Bread Wheat under Normal and Water Deficit Conditions

“…Water deficit reduces nutrients uptake, leaf water content, and photosynthesis, which deleteriously reflect on plant growth and productivity [ 20 , 21 , 22 ]. Furthermore, drought stress induces oxidative stress by raising the production of reactive oxygen species (ROS) [ 23 , 24 , 25 ].…”