Jamila Dirbas (1)* and Ahmad Al Jouma (1)
(1) Cotton Research Administration
(Corresponding author: Dr. Jamila Dirbas. Email: jamila.dirbas@gmail.com Abstract The experiment was conducted at Hama Center for Scientific Agricultural Research during the 2018 and 2019 seasons according to randomized complete block design with three replications. The research aimed to estimate heterosis and combining ability for earliness and yield of F1 hybrids resulted from half diallel program of twelve parents of upland cotton. Analysis of variance indicated to significant differences among the genotypes for all characters. Estimation of relative heterosis and heterobeltiosis showed significant favorite values in some hybrids that reached -6.37%, -5.75* %( Millinium x Aleppo 90, Fantum x Lider) for days to first opened boll, 58.6%, 35.58% (Millinium x Lider) for earliness and 136.22%, 132.61% for single plant yield, respectively. That refers to the variance of parents in genetic factors that control these traits. The percentages of δ2GCA/δ2SCA > 1 for all traits indicated to addictive gene effect. Parent Aleppo 124 was the best general combiner to days to first opened boll (-7.98) while, parent Fantum to earliness % (7.73) and parent Niab 414 (17.31) to single plant yield, therefore they can be used in breeding programs for improving these traits. Hybrid (Fantum x Lider) had the best SCA for days to first opened boll (-8.64), hybrid (Millinium x Lider) for earliness % (32.78), and hybrid (Raqqa 5 x Niab Kiran) for single plant yield (62.19), whereas hybrids; Fantum x Raqqa 5 and Coker 139 x Aleppo 90 had positive and non-significant SCA for earliness % and single plant yield, respectively. Subsequentl,y hybrids had significant favorite values for heterosis and SCA can be used in breeding programs for exploiting hybrid vigor. While Hybrids had positive and non-significant SCA that resulted from general combiner parents can be used to get distinct genetic combinations and breeding work can be followed to develop high yielding anshort-durationon varieties.
Keywords: cotton, earliness, yield, heterosis, combining ability, half diallel.

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