Document Type : Original Article
Author
Vegetable Crops Department, Faculty of Agriculture, Alexandria University, Alex,Egypt.
Abstract
Five commercial tomato (Lycopersicon esculentum, Mill) cultivars and their ten F1 hybrids, in a diallel cross system without reciprocals, were used in this study to detect the general performance, and to estimate heterosis percentages relative to mid parents, potence ratios, general -and specific- combining ability, and heritability percentages in broad and narrow senses for some important characters.
The obtained results reflected generally that the used parental cultivars appeared to have wide ranges of variabilities in the various studied characters and their detected differences were found significant in the most cases . The general performances of the F1 hybrids of some characters reflected the presence of partial-to over-dominance, but with different magnitudes. On the other hand, some other studied characters suggested the presence of partial-to under-recessiveness with different degrees. Positive and desirable heterotic effects were reflected on the performances of most of F1 hybrids for certain characters. On the contrary, negative heterotic effects (undesirable) were also detected on some F1 hybrids for some other characters. The obtained results reflected also that both additive and non-additive gene effects contributed ,with different degrees, to the basic genetic mechanisms involved in the inheritance of all studied characters. However, the non-additive gene effects seemed to be relatively more important than those of the additive effects. These results were also confirmed by the high estimates of ơ2sca relative to those of ơ2gca, the estimated values of potence ratios, and the estimates of both broad-and narrow-sense heritability.
The results indicated also that a particular cultivar or hybrid can not be used to evaluate all studied characters with equal efficiency. However, the best general combiner parent that appeared to have the significant highest positive value of G.C.A. was found to be cultivar ''Super Marmand'' (for the characters plant height ,number of branches per plant and total soluble solids), cultivar ''Peto-86'' (for the characters plant height to the first flower , number of flowers per cluster ,number of fruits per plant and fruit shape index), cultivar ''Edkawy'' (for the characters fruit weight ,fruit diameter ,fruit length and fruit locules number), and cultivar ''Super Strain-B'' (for the character total fruits weight per plant).
The results indicated also that the best hybrid combinations were C x M (for the plant heigh), S x E (for the four characters number of branches per plant, plant height to the first flower , number of fruits per plant ,and total fruits weight per plant), C x P (for the characters number of flowers per cluster and fruit shape index), M x E (for fruit weight), S x M ( for the fruit length character) , P x S( for fruit diameter and number of locules per fruit characters), and the cross P x M (for total soluble solids).
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