Breeding of parental and tolerant hybrids of Theobroma cacao L. to Phytophthora megakarya Bras. and Griff.

The development of resistant varieties can be done according to a genetic approach. Estimation of genetic parameters for the quantitative traits of cocoa genotypes (Theobroma cacao L.) was made from a 5 × 5 diallel mating design. The objective of this study was to identify tolerant genotypes to black pod disease (BPD) through genetic analyzes. The inoculation of the leaves of parental cocoa genotypes and their offsprings with Phytophthora megakarya was performed in the nursery for two seasons (dry and rainy). Percentage success for crosses made using hand pollination was low (31.22%) and fair for grafting (60.68%). Observations made on necrosis length on the 2nd, 4th and 6th days after inoculation showed increasing sensibility of the clones to BPD in the order SNK 413˂T 79/467˂T 79/501˂SNK 16˂SCA 12. 84.37 and 76.04% of hybrid genotypes exhibited positive heterosis (hybrid vigor) in dry and rainy seasons respectively. Narrow sense (h²) and broad-sense (H²) heritabilities was high in two reciprocal crosses [F30 (h²= 0.699 and H²=0.624) and F70 (h²= 0.601 and H²=0.643)]. Key words: Theobroma cacao, Phytophthora megakarya, tolerant, heterosis, heritability.