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.
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.
The field experimentes were conducted during 2016 and 2017 rice growing seasons. The investigation aimed to study the effect of seed classes i.e. breeder, foundation, registered and farmer and the studied cultivars i.e. Sakha 101, Giza 177, and Giza 178 on the productivity of rice (Oriza sativa). Split plot design with three replications was used, the main plots were randomely occupied by four classes of seeds, while the cultivars Sakha 101, Giza 177, and Giza 178 were assigned to the sub plots. Results showed that, breeder seeds gave the highest grain yield (10.97 and 11.34 t ha-1) in 2016 and 2017 seasons, respectively. The highest grain yield (10.51 and 10.83 t/ha) was obtained from variety Sakha 101 in both seasons, respectively. The interaction between cultivars and seed classes was highly significant for germination (%), shoot length (cm), root length (cm), days to heading, number of tillers/hill, panicle weight (g), panicle length (cm), seed set (%), 1000-grain weight and grain yield, while not significant was found for plant height (cm) during 2016 and 2017 seasons. The results indicated that both of rice varieties and seed classes were important for increasing grain yield.
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