الفهرس 
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Abstract
The present study was carried out at the Agronomy Department, Faculty of Agriculture, Tanta University, Experimental Farm of the Rice Research and Training Center (RRTC), Sakha Research Station, Kafr El-Sheikh Governorate, Agricultural Research Center (ARC), Egypt and the north of Delta (El-Sirw location) during the two successive rice-growing seasons of 2020 and 2021. For nine genotypes of rice (Oryza sativa L.) and 18 crosses were chosen and tested under salinity stress conditions, including Egyptian commercial varieties, promising lines, and introduced varieties representing a diverse range of genetic materials, to examine the magnitude of yield. The present investigation was carried out to study combining ability, heterosis and genetic diversity during the two successive growing seasons of 2020 and 2021. That was designed through line x tester analysis. The main objective of study is addressing the inheritance of some morphological, physiological, yield and its component associated with salinity. Nine genotypes namely; GZ1368, GZ9399, and IR45427 were used as tester, whereas the cultivars Giza178, Sakha 104, Giza 177, GZ10365, Giza 179 and SAL010 were utilized as lines. where these genotypes have a wide range of variation due to their different genetic background in salt tolerance. Therefore, breeding salt-tolerant varieties of rice is necessary and inevitable to overcome this problem. The grains of nine parents were seeded during the 2020 growing season. After thirty days, seedlings from each parent were separately planted in two rows on the permanent field that were five meters long and spaced 20 x 20 cm away from one another. The six lines were crossed with the three testers during this season’s blooming to create 18 F1 hybrid seeds using the bulk emasculation procedure with hot water (42–44 °C for 10 min). Between May 15 and May 30, 2021, hybrid seeds from 18 F1 crossovers were sowed at the nursery. The seedlings from the parental lines and their crosses were transplanted as individual plants or hills after 30 days, with plant spacing of 20 × 20 cm and 5 m for each row. A randomized whole block design with three replications was used for each planting date. Rice’s recommendations were followed in all agricultural practices. For the parents and F1 generations, data were recorded on five individual plants that were randomly sampled from each plot and data were recorded on them. The aim of this study to examine the response of various genotypes to salt stress, to find some molecular, physiological, and crop evidences associated with salinity tolerance. As well as to study some important rice plant genotypes to determine the relative performance of the average performance, the strength of the hybrid, the effects of general and specific ability to damage, the genetic components, the degree of heritability. The following parameters were recorded: Morphological characters: • Number of days to 50% flowering (day) • Plant height(cm) • Flag leaf area (cm2) • Flag leaf angle (O) Physiological characteristics 1- Chlorophyll content. (SPAD). 2- Leaf temperature (OC). 3- The percentage of CO2. 4- Na/K concentration (%). Yield and its component characters: 1. The number of panicle/plants. 2. Panicle length (cm). 3. Panicle weight (g). 4. Weight of 1000 grains (g). 5. The number of filled grains / Panicle. 6. Sterility (%). 7. Grain yield (g) / plant. 8. Harvest Index (%). The results obtained could be summarized as follows: A) Analysis of variances: 1. The analysis of variances cleared highly significant mean squares for genotypes. 2. These differences between mean square values for lines x testers were highly significant for all studied traits, indicating that dominance genetic variance (non-additive) were of great importance in the inheritance of these characters. 3. The interactions of genotypes, parents, crosses, parents vs. crosses, lines, testers and line x testers were found to be significant for all studied morphological and yield and its component traits. Therefore, the analysis of all sources of variation demonstrated the presence of genetic variability within the genotypes for these characters. 4. GCA/SCA ratio were found to be less than unity for morphological and yield and its component traits, indicating that the dominance gene action (non-additive) was of greater importance in the inheritance of these traits. It suggested greater importance of non-additive gene action in their expression and indicated very good prospect for the exploitation of non-additive genetic variation for yield and its component traits through hybrid rice breeding. B) Mean performance: 1- Days to 50% heading: the results showed that parents GZ10365, GZ9399 and hybrid combination Sakha 104 x GZ9399 were the earliness with high differences compared with all other, line, testers and hybrids, respectively. 2- Plant height: Giza 179 cultivar, GZ9399 strain and Sakha104 x GZ1368 hybrid, which gave the lowest values for plant height. 3- Flag leaf area: Both parents Giza 178, SAL010 and the hybrid Giza 178 x IR45427 gave the highest mean values. 4- Flag-leaf angle: parent Giza 178, tester GZ1368 that gave the desirable value, for the hybrid combination Giza 178 x GZ1368 that gave erect flag leaf angle for the hybrids. 5- Chlorophyll content: the parents Sakha 104 and GZ10365 as well as the cross Giza 178 x IR45427 showed the highest content of chlorophyll in the leaf. 6- Leaf temperature: the parents Giza178 and Sakha104 and the hybrid combination Sakha 104 x IR45427 showed the lowest mean values. 7- CO2 Diffusion: The results showed that the parents SAL010 and GZ9399 and the hybrid Sakha104 x IR45427 gave the highest rate of CO2 diffusion. 8- Na/K Ratio: the parents SAL010 and GZ9399, as well as the hybrid Giza 177 x IR45427, showed the lowest percentage of Na+ /K+. 9- Number of panicles/plants: Parents SAL010, Sakha 104 and hybrid Giza 178 x GZ1368 showed the highest rate of panicles/plant. 10- Panicle Length: we find that the parents Giza 179 and GZ1368 and the cross Giza 178 x GZ9399 showed the highest values in panicle length. 11- Panicle weight: the parents Giza 178 and GZ1368 showed the highest average panicle weight, as well as the hybrid Giza 178 x GZ1368 gave the desirable mean values. 12- Number of filled grains / panicle: the parents Giza 178 and GZ1368 and the hybrid GZ10365 x GZ9399 showed the highest number of filled grains per panicle. 13- Sterility (%): the parents Giza 179 and GZ1368 showed the lowest rate of sterility, as well as the resulting hybrid Giza 177 x GZ9399. 14- 1000 grains weight: Both parents, Sakha 104 and GZ9399, as well as the hybrid GZ10365 x IR45427, showed the highest mean values. 15- Grain yield per plant: the parents Giza 179 and GZ1368, which gave the highest values weight of individual plant yield. As for the hybrids, Giza 178 x GZ1368 gave the highest grain yield per single plant compared to other hybrids. 16- Harvest Index %: the parents Giza 179, GZ9399, and GZ9399x Sakha 104 hybrids recorded the highest mean for harvest index compared to other parents and hybrids. C) Combining abilities: I. General combining ability: 1. Among the genotypes, we find that the genotypes SAL010, Giza 178, 177 Giza, Giza 179, Sakha 104, and GZ10365 showed that they have a general ability to combine morphological, physiological and yield traits under study, and as for the markers. We find that the testers IR454274, GZ9399 and GZ1368 have a general combing ability of the traits under study. 2. Highly significant positive values of GCA effects would be interest in most traits under study, except for plant height, days to 50% heading, Leaf temperature, sterility % and percentage of Na+ /K+ whereas the highly significant negative values would be useful from the breeder’s point of view. II. Specific combing ability: 1. Morphological traits: from estimates of specific combining ability effects (SCA) of the hybrid combinations, could be concluded that, for days to 50% flowering, the cross combinations Giza 178 x GZ1368 was the best specific combination for earliness. For plant height, the cross combination GZ10365 x IR45427 was the best specific combination for plant height. Concerning flag leaf angle, the cross-combination Giza 177 x GZ1368 was the best specific combination for this trait. For flag leaf area, the cross combination GZ10365 x GZ9399 was the best specific combination for flag leaf area. 2. Yield and its component traits: the results revealed that hybrids Giza 177 x GZ9399 , Giza 178 x GZ1368 , Giza 177 x GZ1368 , Sakha 104 x GZ1368 , Sakha 104 x IR45427, GZ10365 x GZ9399, Giza 178 x IR 45427, GZ10365 x IR45427 ,Sakha 104 x GZ9399 had the best SCA for all studied (day to heading , plant height ,flag leaf area, falag leaf angle , Chlorophyl content , Leaf temprture, co2 , Na+ /K+ , Number of panicle / plant , panicle length, panicle weight , 1000 grain weight , number of filled grains , sterility % , Grain yield and Harvest index. 3. These results indicated that, the possibility to exploit these combinations in developing rice varieties for salinity tolerance. It also indicated that both additive and non-additive types of gene action play important for the inheritance of these traits. D) Genetic parameters and heritability: 1. Genetic parameters, as well as, heritability values were estimated for all studied morphological traits. The results indicate that, the estimates of the dominance variance (2D) and the relative importance of SCA % for all morphological traits were higher than those additive variance (2A) and relative importance of GCA%. These findings indicated that, the former characters were largely governed by dominance gene action. Whereas, the dominance genetic variance played the more important role in this case. Also, high values were determined in broad sense for all morphological, physiological, and some yield traits. On the other hand, low narrow sense heritability values were estimated for these traits. 2. The results showed that, the additive genetic variance as a portion of the total genetic variance was larger than the dominance genetic variance of panicle weight, number of filled grains per panicle, sterility %, grain yield per plant and harvest index %, whereas the additive genetic variance played the more important role in this case. 3. These results indicated that, these traits were not influenced by environmental effect. These means that, selection for panicle weight, number of filled grain per panicle, sterility %, grain yield per plant and harvest index % might be practiced successfully in elate generations. Also, high values were determined in broad sense for all morphological and some yield traits. E) Heterosis effects: 1- Morphological traits: the most pronounced useful heterotic effects relative to the better and mid parents where the results showed that, the hybrid combination Giza 179 x GZ1368 has a high hybrid vigor for earliness and the hybrid Sakha 104 x GZ9399 for shortness. As well as the two hybrids Giza 177 x GZ1368 and Sakha 104 x GZ1368 for leaf area flag and hybrid Giza 177 x GZ1368 for the angle of the flag leaf. 2- Physiological traits: The results showed that the hybrid Giza 178 x IR45427 for the chlorophyll trait, the two hybrids Giza 178 x GZ1368 and Sakha 104 x IR45427 for the trait for temperature and Giza177 XZ9399 the Na+/K+ ratio. As well as the hybrid Sakha104 x GZ9399 for Co2 Diffusion had the highest values in the heterosis respectively. 3- Yield traits: The results showed that the Sakha 104 x IR45427 hybrid had high hybrid vigor for the number of panicles, and the two hybrids GZ10365 x IR45427 and Giza 178 x GZ9399 had hybrid vigor for the characteristic of panicle length, and the Giza 177 x IR45427 hybrid had high hybrid vigor for the panicle weight. Whereas the hybrid GZ10365 x IR45427 had high hybrid vigor for 1000 grains weight and the Giza 178 x GZ9399 hybrid has a high hybrid vigor for the number of filled grains / panicle. Under the study, and for the characteristic of harvest index, the Sakha 104 x GZ9399 hybrid gave high and positive hybrid vigor.