Broadening the Gene Pool of Cocoa (Theobroma cacao L.) Progenies with Guiana Clones: Establishment and Precocity Traits

摘要

Guiana (GU) cocoa is one of the recently identified genetic groups with high resistance to black pod diseases. The objective of this study was to estimate combining abilities of selected GU clones for traits related to establishment ease and precocity. Three tester clones were crossed with eight GU clones as males in a 3 x 8 factorial mating design to produce F_1 progenies. These progenies were evaluated together with four standard varieties at two locations in Ghana for percentage survival, stem growth, jorquette height, canopy spread, flowering intensity, and pod number. The GU progenies surpassed on average the standards for all traits except for jorquette height at one location. Preponderance of additive effects was manifested as significant general combining ability (GCA) estimates of female and male clones for all traits. The specific combining ability (SCA) was significant only for flowering intensity, stem growth, and pod number. GU 341H and GU 225V contributed positively to GCA ejfects forall traits studied. Based on establishment and precocity traits, the Guiana population represents a suitable genetic resource for broadening the genetic base of cocoa breeding.