The investigation was undertaken to determine the combining ability effects different genetic parameters between some rice genotypes. Line x tester mating design was conducted and 12 F1 hybrid combinations were developed from the cross between 3 lines and 4 testers. There was significant difference between parents, crosses and line x tester interaction for the tested traits. Sakha106 was the best general combiners for heading date, while the line GZ9399 was the best for yield and its components. Among the testers, GZ10101 line was adjudged as good general combiner for 1000-grain weight trait. The crosses Giza178 x Egyptian Yasmin and Sakha106 x GZ10101 were the best hybrid based on specific combining effects for the most important traits. The dominance genetic variance (σ 2 D) was greater than the additive genetic variance (σ 2 A) in controlling the inheritance of all the studied traits, except flag leaf area was governed by the additive genetic variance. Heritability values are high for plant height and sterility %, indicating slight effects of environment on the traits. On the contrary, the contributions of the lines were higher than the contribution of the testers for no. of panicles/plants, no. of filled grains/panicle, sterility % and grain yield/plant. Cluster analysis divided the seven rice genotypes and their hybrid combinations into two main groups based on morphological traits especially plant height, no. of filled grains/panicle traits and sterility %. Studying of combining abilities is effective in identifying the better parents and helps in the selection of better parent for successful breeding.
The experiment was carried out in strip plot design with three replications to evaluate 14rice genotypes under normal and water deficit in the field and biotechnology lab of Rice research and Training Center at Sakha Agricultural Research Station, Sakha, Kafr EL-Sheikh Egypt, during2021 and 2022summer seasons. Results revealed a wide variation among rice genotypes and their parents for agronomical characteristics and SSR markers. Data showed that days to maturity, plant height, Flag leaf area, number of panicle-1 , Panicle length, number of filled and unfilled grains panicles-1 as well as grain yield t ha-1 were significantly affected by irrigation treatments. Grain yield was affected significantly according to the genotypes and irrigation treatments. The combination between Egyptian Yasmin with normal irrigation produced the highest values of grain yield with the lowest percentage(14.58%) of yield reduction compared to its production under water deficit conditions. While, the lowest values of grain yield were obtained with Nerica7 (V2) under water shortage conditions with the highest percentage(33.63%) of yield reduction compared to its production under normal irrigation. Fifty SSR markers were used for estimating the genetic variation among the 14rice genotypes. Rice genotypes were divided into two main groups based on the polymorphism revealed by the SSR markers. The first group has the aromatic genotype, Egyptian yasmine and the promising newly developed genotype No.2. While, the second main group has the other tested rice genotypes, NERICA7 and the other genotypes. The data indicated that phenotypic variance was generally superior than genotypic variance for all studied traits.
Stability analysis for some Egyptian rice cultivars was studied in this paper to identify high-yielding stable rice varieties and to determine their suitable areas as well as their adaptability to different climatic and topographic conditions. A field experiments for ten rice varieties were evaluated by designing randomized complete block with three replications in five successive rice growing season from 2016 to 2020at three Agricultural Research Stations (Sakha, Gemmeiza and Zarzoura) in Egypt. Result of ANOVA analysis showed high significance in the studied cultivars, environment and genotype-environment interaction indicated that there is genetic diversity among the cultivars yield. Based on the performance of the rice cultivars across the locations, highly promising for grain yield among cultivars studied, the cultivars Giza 178, Sakha 103, Sakha 104, Sakha 101 and Sakha 106 were considered stable and adapted under different environments. Furthermore, the results indicated that studied cultivars slightly differ in their response to the various environmental conditions, which suggested the importance of cultivars assessment under many environments due to identification the best genetic make up for a particular environment.
High temperature is a major environmental stress factor limiting rice productivity. The present investigation was carried out to evaluate and identify heat tolerant rice genotypes on the basis of heat indices and SSR markers. Fifteen rice genotypes were designed in Randomized Complete Block Design (RBCD) with three replications under well-watered and heat stress conditions at two environmentally different sites (Sakha and New Vally) during 2018 and 2019 rice season. Parameters of heat indices were calculated based on grain yield under both conditions. The results indicated that the heat tolerant index (HTI) and mean productivity (MP) index had the highest correlation with yield under two the conditions, Giza178, Giza179, Giza182, Egyptian Yasmin, Egyptian Hybrid1 and N22 were the best genotypes based on indices values, representing high temperature tolerance of these genotypes. Results of variance analysis of yield and other traits in both conditions showed that there was a significant difference among genotypes and their traits. Egyptian hybrid 1 produced the highest mean values of grain yield/plant under normal and heat stress conditions (50.26 and 37.00 g/plant), meanwhile Sakha102 had the highest reduction (70.36%) and N22 had the lowest reduction (23.9%).All genotypes clearly grouped into two major clusters in the dendrogram at 58% similarity based on Jaccard's similarity index. The first cluster represents the Indica and Indica/Japonica tolerant rice genotypes for high heat, while the second cluster represents the Japonica sensitive genotypes for high heat.
The aim of the current study was to evaluate 25 rice genotypes under normal at Sakha, Kafr El-Sheikh, Egypt and under heat stress conditions at New Valley, Egypt during two rice growing seasons of 2017 and 2018. Data were collected on eight traits i.e., flag leaf area, flag leaf angle, plant height, panicle length, panicles plant -1 , 1000-grain weight, fertility percentage and grain yield plant -1 . High amount of genetic variation was found among the studied genotypes under normal and heat stress conditions. All studied genotypes were negatively affected by high temperature. The most affected traits by heat stress were fertility percentage, grain yield plant -1 , flag leaf area and panicles plant -1 with average reductions of 73.59, 64.22, 42.46 and 41.31%, respectively. Correlation and path coefficient analysis showed that number of panicles plant -1 and fertility percentage were good indicators for grain yield under heat stress condition. Based on the HSI values of grain yield plant -1 and fertility percentage, both genotypes N22 and Giza178 could be identified as heat tolerant (HSI value was ≤0.5 for both traits). Based on the results of PCA analysis, the most desirable genotypes under heat stress were Giza178, N22, Bala, Dular, WAB56-104, Sakha104 and Egyptian Yasmin. According to the current investigation, it could be concluded that those eight genotypes could be used in breeding programs as donors for developing high yielding heat tolerant promising lines. In addition, Egyptian rice varieties; Giza178, Sakha104 and Egyptian Yasmin are suitable for cultivating under both normal and heat stress conditions in Egypt.
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