Breeding Value of Cocoa (Theobroma cacao L.) for Pod and Bean Traits: A Consequential Advance in Nigerian Cocoa Breeding Program
Keywords:combining abilities; heterosis; line and tester analysis; parents; progenies
The understanding of the generated hybrids’ breeding value gives a measure of probable advances in a breeding program. Four cocoa genotypes (testers) were crossed with two distinct lines (T65/7 and T86/2). The parents and the hybrids were separately established in randomized complete block design with six replications. The fourteen genotypes were evaluated for pod length (PL), weight (PW), beans/pod (NoB), bean length (BL), width (Bwi) and thickness (BT). The treatment, parent, crosses and Line x Tester sources of variation were significant (P ≤ 0.05). Hybrids from the same maternal parent differed significantly (P < 0.05) for the six traits. Contribution to the total variance of PL, PW and Bwi were in the following order: Tester > Line x Tester > Lines. The highest general combining ability (0.42) occurred in T65/7 for PW; the least (-0.081) occurred in T86/2 for PL. Cross combination T65/7xT57/22 produced the highest specific ability of combination (4.33) for NoB. Variance of GCA and SCA were significant (P < 0.05) for the six traits. The GCA/SCA ratios revealed the inheritance of PL, PW, Bwi and BT to be additive. Non-additive gene effect controlled NoB and BL. Heterosis for the six traits ranged between -17.82% for BT (T65/7xT57/22) to 52.40% for PW (T65/7xT53/8). Increased productivity in cocoa is possible through hybrid breeding programs.
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