Average degree of heterosis in sweet potato [electronic resource]

Includes references.

Two field experiments were conducted at two locations; Menofiya and Barrage Experimental Stations, during the period 1990 up to 1997 to develop new sweet potato cultivars through studying the behaviour at different breeds resulting from crosses to obtain good vegetative growth and high yield. The obtained results could be summarized as follows, as for the number of leaves on main stem of the 25 F1 crosses studied seven ones showed significant positive heterosis values based on their respective mid parent (MP) suggesting dominance towards the high number of leaves. The cross "55 x 66/2" gave the highest (ADH) value 66.76 %, followed by the crosses 55 x 66/3 and 55 x 66/4 with 55.68 % and 27.6 %, respectively. No dominance for this trait was observed in four crosses, i.e. 55 x 3411, 55 x 3414, 55 x 34/5 and 55 x 21011, since they had insignificant ADH values (-0.40, 012, -0.58 and 2.67 %, respectively) in relation to their mid parent (MP). Obtained potence ratio values in these crosses which were near to zero (-0.01, 0.00,- 0.02 and 0.25, respectively, supported the no-dominance hypothesis. On the other hand, dominance toward the low number of leaves was detected in 14 F1 hybrids. They gave significant negative heterosis values ranging from (-5.07) in the cross 55 x 210/2 to (-31.11 %) in the cross 55 x 171/4. For the leaf area the heterosis percentages based on (MP) and (HP) ware ranged from (- 29.22 %) to 143.02 % and from 7.46 % to 130.5 %, respectively in the first season. Of the studied 25 F1 hybrid, 22 F1,s gave significant positive heterosis values based on their respective mid parent, suggesting dominance towards the large leaf area.

Summary in Arabic.

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