Heterosis is very important phenomenon where the superior performance can appear in F1 hybrid because increasing vigorous growth which leads to healthier and faster growing plants compared to its parents. This investigation was carried out at the experimental farm of Sakha Agricultural Research Station, Kafr El-Sheik, Egypt, during 2019 and 2020 rice growing seasons to study heterosis and simple correlation of the yield and its components traits in some hybrid rice combinations, using Line x tester design among six cytoplasmic mail sterility and four restorer genotypes. The results of heterosis over mid parents and heterosis over better parent represents that the best hybrids were PR1xIR69625A, PR78xIR68902A, PR78xIR58025A, PR78xIR69625A and PR1xIR58025A could use in breeding program to improve the grain yield dependent on its superiority in many traits. The additive variance (σ 2 A) was greater than the dominance variance (σ 2 D) for the duration and panicle weight in both seasons and head rice in 2 nd growing season. Contrarily, the dominance variance (σ 2 D) was the greatest variance for the rest traits, indicating that these traits were largely governed by non-additive genes action. Grain yield exhibited highly significant and positive correlation with total biomass in both seasons and with panicle weight in 1 st season, indicating the selection based on these two traits will be more effective to improve the grain yield.
The investigation was carried out at the experimental farm of Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt, during 2018, 2019 and 2020 rice growing seasons. The aim of this study was to estimate the genetic statistics of the important traits in some hybrid rice combinations, 24 hybrids were produced by crossing six CMS lines with four testers and then evaluated in two seasons. Line x tester analysis showed highly significant difference in mean squares for genotypes of most traits. The best genotype was the hybrid PR78/IR58025A for grain yield indicating that it can be used in breeding program to improve grain yield. Furthermore, concerning the (GCA) the good combiners for studied traits were PR78 and IR58025A for grain yield, PR78 and IR69625A for biomass. These genotypes can transfer the superiority to their offspring in hybrid combinations. In addition, the most promising hybrids which have the highly significant SCA effects for grain yield wasPR2/IR69625A and could be used in breeding program.
Fourteen rice hybrids were grown in the two successive seasons 2020 and 2021 in Kafr El-Sheikh, Egypt, at the Experimental Farm of Rice Research and Training Center to evaluate the presence of variation for investigated traits and to estimate correlations for the studied traits with the grain yield. Every analyzed trait revealed substantial variations between hybrids, indicating a wide range of genetic variability controlling the studied traits. Grain yield (t ha -1 ) and 100-grain weight attributes with IR69625A×GZ6296, IR58025A×GZ6296 and G46A×GZ6296 hybrids achieved the highest estimated values and the hybrids IR70368A×PR78 and Pusa13A×Giza181 in in the grain yield only. Five hybrids showed surpass over standard check variety, EHR1 for grain yield and some other traits. A strong positive correlation and regression was found between grain yield (t ha -1 ) and the following variables: panicle length, number of spikelets panicle -1 , harvest index and biological yield (t ha -1 ) and it can be dependent on these trait to select the best genotypes in breeding program to improve the grain yield.
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