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. 2022 Mar 5;11(5):702.
doi: 10.3390/plants11050702.

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

Raghda M Sakran  1 , Mohamed I Ghazy  1 , Medhat Rehan  2   3 , Abdullah S Alsohim  2 , Elsayed Mansour  4
Affiliations

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

Raghda M Sakran et al. Plants (Basel). .

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.

Keywords: cluster analysis; drought stress; gene action; genetic diversity; heterosis; principal component analysis; rice.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Boxplots for days to heading (A), plant height (B), leaf rolling (C), relative water content (D), chlorophyll content (E), number of panicles/plant (F), number of filled grains per panicle (G), sterility % (H), 1000-grain weight (I), and grain yield per plant (J) under well-watered and water-deficit conditions.
Figure 2
Figure 2
Mean performance of the six rice parents and their 15 F1 crosses for days to heading (A), plant height (B), leaf rolling (C), relative water content (D), and chlorophyll content (E) under well-watered and water-deficit conditions. The bars on the columns correspond to LSD (p ≤ 0.05).
Figure 3
Figure 3
Mean performance of the six rice parents and their 15 F1 crosses for number of panicles per plant (A), number of filled grains per panicle (B), sterility % (C), 1000-grain weight (D), and grain yield per plant (E) under well-watered and water-deficit conditions. The bars on the columns represent LSD (p ≤ 0.05).
Figure 4
Figure 4
Dendrogram of the phenotypic distances among six rice genotypes and their 15 corresponding crosses based on four drought tolerance indices. The genotypes were categorized into three groups: A is drought-tolerant; B is moderately drought-tolerant; and C is drought-sensitive.
Figure 5
Figure 5
PCR amplified fragments for the SSR markers RM263, RM223, RM234, and RM3805 with the six parental rice genotypes. M is a 100 bp DNA ladder.
Figure 6
Figure 6
Dendrogram generated from UPGMA cluster analysis of the six parental rice genotypes based on SSR markers.
Figure 7
Figure 7
Biplot of principal component analysis exploring the association among the studied traits under water-deficit conditions.
See this image and copyright information in PMC

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