Abstract
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 413Ë‚T 79/467Ë‚T 79/501Ë‚SNK 16Ë‚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.
Highlights
Cocoa is native to tropical America and is a cash crop in many tropical countries
In Cameroon, approximately 80% of its production losses caused by black pod disease (BPD) in areas where climatic conditions are favorable (Despréaux et al, 1988)
Improvement programs are increasingly focused on developing hybrids that are tolerant to BPD but information on its genetic control has not been fully elucidated
Summary
Cocoa is native to tropical America and is a cash crop in many tropical countries. It is an important source of foreign exchange, but several factors account for its low productivity. Some of these factors include aging plantations (Tijani, 2005), poor farming practices, presence of insects, presence of rodents and disease infestations especially black pod disease (BPD) (Ndoumbe-Nkeng, 2002). Improvement programs are increasingly focused on developing hybrids that are tolerant to BPD but information on its genetic control has not been fully elucidated
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