The present investigation was conducted to determine the magnitudes of combining ability and heterosis obtained from hybrids three produced by utilization of CMS, maintainer and restorer lines in rice. The experiment was carried out during the two growing seasons of 2010 and 2011 at Rice Research and Training Center (RRTC) Farm, Sakha, Kafr El-Sheikh, Egypt. Twelve F1 hybrids were obtained from crossing three CMS lines as female parent with four restorer lines. These hybrids were evaluated along with their parents for genotypic variances. The analysis of variance revealed highly significant differences among genotypes, parents, parents vs. crosses for days to heading (day); plant height (cm); panicles plant-1 ; panicle length (cm); filled grains panicle-1 ; spikelets fertility% and grain yield plant-1 except parents vs. crosses for panicle length (cm). The variance among males (testers) were either significant of highly significant for all studied traits. The variances among crosses due to males and females (lines x testers) interactions, showed highly significant SCA effects for all the studied traits except for plant height (cm). The estimated values for variance of general combining ability (σ²GCA) were less than specific combining ability variance (σ²SCA) for all studied traits except plant height (cm). This result indicated the preponderance of non-additive gene action. It was supported by the ratio of (σ²GCA/ σ²SCA) which was less than one for all studied traits except for plant height (cm), indicating that the non-additive type of gene action played a major role in the inheritance of these traits. Heritability estimates in broad sense (h 2 b%) were high for all studied traits. However, heritability estimates in the narrow sense (h 2 n%) were moderate for days to heading (day) (44.58%), plant height (cm) (45.81%) and filled grains panicle-1 (53.80%) and low for the other traits. Three parental lines viz.; IR69625A; G46A and GZ9057-6-1-3-2 were identified as good general combiners for grain yield plant-1 (g). Hybrid combinations as G46A x Giza178; IR69625A x GZ6296-12-1-2-1-1 and Large stigma A x GZ9057-6-1-3-2 showed high mean performances due to the presence of SCA effects.

The main objective of this investigation was to determine the genetic parameters, heritability in both broad and narrow senses, combining abilities and correlation for yield and yield component traits in squash (Cucurbita pepo, L.). For this purpose, five squash varieties were used .These varieties were: Eskandrani (P1); Zucchino tondo di piacenza (P2); Black beouty (P3); Zucchino romanesco (P4) and Coppi (P5). During the summer season of 2011, acomplete diallel crosses mating design was made to evaluate the performances of the 20 F1 hybrids including the reciprocal will their five parental varieties in afield trial at the Experimental Station, Faculty of Agriculture, Mansoura University. Data were recorded on the following traits, number of fruitsper plant (No.F./P.), fruits yield per plant (F.Y./P.Kg), fruit length (F.L.cm), fruit diameter (F.D.cm) and fruit shape index (F.Sh.I). The results indicated that the mean squares for all genotypes were highly significant for all yield and yield component traits. The results of means showed that Eskandrani (P1) was the highest parent for Number of fruits per plant No.F./P. the parental variety Zucchino romanesco (P4) was the highest variety for F.L.cm and F.Sh.I. However, the highest F1 hybrid for fruit yield per plant was Eskandrani (P1) × Zucchino tondo di piacenza (P2) with the mean value of 11.24 kg. Whereas, the highest F1r hybrid was Zucchino romanesco (P4) × Eskandrani (P1) with the mean value of 10.51 kg. The results revealed that the GCA effects (gi) were highly significant for the two parents: Eskandrani (P1) and Zucchino romanesco (P4) for F.L.cm, F.D.cm and F.Sh.I traits. At the same time, the results also revealed that the GCA effects were highly significant for the parents: Zucchino tondo di Piacenza (P2) for F.L.cm and F.D.cm; Black beouty (P3) for F.D.cm and F.Sh.I and Coppi (P5) for F.Sh.I. The results indicated the importance of both (GCA) and (SCA) combining abilities. General combining abilities (GCA) were larger than specific combining abilities (SCA) for all yield and yield component traits except fruits yield per plant (F.Y./P.Kg). The estimates of heritability in broad sense (h 2 b) were larger in magnitudes than those of narrow sense (h 2 n) for all studied traits. The values of heritabilities in broad sense ranged from0.513 to 0.894 for yield and yield component traits.

Gene action for some economical traits in squash was examined by 6 x 6 diallel crossing excluding reciprocals using four foreign varieties, as well as, two local varieties. These varieties were belonging to the species of Cucurbita pepo, L. All 21 genotypes , included six parents and their 15 F1 hybrids were evaluated in the following two locations; Sakha Research Station in Kafr El-sheakh and private farm at Mansoura-Dakahila governorate. Data of vegetative and flowering traits were recorded on plants within plots on the two types. The obtained results revealed that the mean squares of genotypes and its components, GCA and SCA were highly significant for all studied traits, indicating that additive and non-additive genetic variance contributed in the inheritance of the studied traits.Both GCA and SCA genetic variances were found to be highly significant for all studied traits indicating the importance of both additive and non-additive gene action .The parental, Zucchino Nova Verde di Milano were seemed to be the best combiner for number of leaves plant -1 and No. of male flowers plant -1 . While, Arab Marrow was the best combiner for stem length, leaf area (cm 2 ) and No. of female flowers plant -1 . The crosses involving the above parents were promising because they showed highly significant estimates of SCA effects.

This study aimed to estimate significance of heterosis, combining ability, genetic parameters and heritability for vegetative, flowering, yield and fruit quality traits using15 F1 hybrids obtained from 6×6 half diallel mating system without reciprocals. The results indicated that analysis of variance exhibited highly significant for the mean squares of the genotypes for all traits, except for, parents which was significant for fruit diameter and parents vs. hybrids was insignificant for average fruit weight and fruit diameter, but it gave significant for fruit length. None of the F1 hybrids had the highest values for all traits. The maximum significant desirable heterosis values over mid-parent were-17.

During 2010 and 2011seasons, two field experiments of rice experimental farm of Sakha, Kafr El-Sheïkh, Egypt, were performed through a 6 x 6 diallel system analysis to investigation the combining ability and heterosis and their component features of rice under normal irrigation and drought stress conditions.A broad range of genetic variation among research genotypes was indicated by the routine analysis of variance. As for all the features of normal irrigation and drought stress conditionsThe significance of non-additive genetic variation in the heritage of grain yield / plant has been established by GCA / SCA ratios. While the selection based on the accumulation of the additive effect will boost yield and assign it successfully. According to drought susceptibility index (DSI), four parents and six crosses were the lowest genotypes affected by drought.GCA shows all parental lines are intrinsically performing with a strong index of their overall ability to blend. The combinations of IR7887-176-B-2-B X IR80508-B-194-1-B to boost the output of grain per plant was the best possible cross, as reported by SCA.Under drought, the highest values significant for heterosis from better parent, five crosses for panicle length and seven crosses for number of branches / panicles and grain yield characters. In the general sense, higher heritability levels emerged in normal irrigation; genotypic variances played a major part in phonotypical yield variances and their components.Lower and moderate heritage tests for all yields and their components showed that selection for these characteristics would be successful in late generations.