It is crucial to understand how targeted traits in a hybrid breeding program are influenced by gene activity and combining ability. During the three growing seasons of 2015, 2016, and 2017, a field study was conducted with twelve cotton genotypes, comprised of four testers and eight lines. Thirty-two F1 crosses were produced in the 2015 breeding season using the line x tester mating design. The twelve genotypes and their thirty-two F1 crosses were then evaluated in 2016 and 2017. The results demonstrated highly significant differences among cotton genotypes for all the studied traits, showing a wide range of genetic diversity in the parent genotypes. Additionally, the line-x-tester interaction was highly significant for all traits, suggesting the impact of both additive and non-additive variations in gene expression. Furthermore, the thirty-two cotton crosses showed high seed cotton output, lint cotton yield, and fiber quality, such as fiber length values exceeding 31 mm and a fiber strength above 10 g/tex. Accordingly, selecting lines and testers with high GCA effects and crosses with high SCA effects would be an effective approach to improve the desired traits in cotton and develop new varieties with excellent yield and fiber quality.

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Water shortage is a serious climatic factor that drastically limits rice productivity. Thereupon, the development of better adapting rice genotypes under water deficit stress is imperious to maintain rice yield to ensure food security worldwide. The current study focused on genetic variability of morpho-physiological traits of rice to discover relationships between morpho-physiological and yield contributing traits under drought stress conditions in 24 rice genotypes during 2019 and 2020 seasons. Results showed highly significant mean squares of combined analysis for treatments and environment of all studied traits under normal and drought stress conditions. Results reported that the earliest rice cultivars were Giza177 and Giza179; however, the highest yield and its components traits were detected for Giza179, followed by Giza178, Sakha101 and Sakha108 under normal and water deficit conditions; moreover, generally, PCV was higher than GCV for all studied traits. High heritability coupled with high genetic advance was noted for plant height and relative water content under normal and drought conditions, suggesting a preponderance of additive gene action in expressing these traits that could be improved by selection in early segregating generations. While, high heritability coupled with moderate genetic advance was noticed for duration, grain yield/plant and harvest index under both conditions. Giza179 and Giza178 showed the best values for drought tolerance and were produced from same genetic background. Moreover, grain yield/plant showed a highly significantly positive correlated with panicle length, number of panicles/plant, panicle weight and 100-grain weight under normal and water deficit conditions; moreover, these traits were the main components of grain yield, so any selection based on these traits may lead to enhancement in grain yield. As a result, Giza178 and Giza179 varieties can be introduced as donors in breeding programs to tolerate water shortages to improve morphological and yield characteristics.

To generate high-yielding cultivars with favorable fiber quality traits, cotton breeders can use information about combining ability and gene activity within a population to locate elite parents and potential F1 crosses. To this end, in the current study, twelve cotton parents (eight genotypes as female parents and four testers) and their F1 crosses obtained utilizing the linex tester mating design were evaluated for their general and specialized combining abilities (GCA and SCA, respectively) of yield traits. The findings showed that for all the investigated variables, variances owing to genotypes, parents, crosses, and parent vs cross showed extremely significant (P ≤ 0.01) differences. Additionally, throughout the course of two growing seasons, the mean squares for genotypes (parents and crosses) showed strong significance for all the variables under study. The greatest and most desired means for all the examined qualities were in the parent G.94, Pima S6, and tester G.86. The best crossings for the qualities examined were G.86 (G.89 × G.86), G.93 × Suvin, and G.86 × Suvin. The parents' Suvin, G89x G86 and TNB were shown to have the most desired general combining ability effects for seed cotton yield/plant, lint yield/plant, boll weight, number of bolls/plants, and lint index, while Suvin, G.96 and pima S6 were preferred for favored lint percentage. For seed cotton yield, lint percentage, boll weight, and number of bolls per plant per year, the cross-G.86 x (G.89 × G.86) displayed highly significant specific combining ability impacts. The crosses G.86 × Suvin, Kar x TNB, G.93 × Suvin, and G.93 × TNB for all the studied traits for each year and their combined were found to have highly significant positive heterotic effects relative to better parent, and they could be used in future cotton breeding programs for improving the studied traits.