Assessing the Tolerance of Cocoa (Theobroma cacao L.) Progenies to the Black Pod Disease Caused by Phytophthora megakarya Bras. and Griff.

Abstract

The cocoa (Theobroma cacao L.) is a cash crop of great economic importance to some cocoa-growing countries. However, diseases and pests, including black pod disease caused by Phytophthora megakarya, can cause yield losses of up to 100% if no phytosanitary treatment is applied. Thus, the aim of the present study is to evaluate the tolerance of five cocoa hybrids developed by IRAD (PA107*SNK614, IMC67*SNK109, SCA12*SNK16, IMC67*SNK64 and T79/501*SNK64) against black pod disease in relation to the parent clones.  Mature pods (approximately 5 months old) were harvested and used to assess black pod tolerance using the Iwaro Detached Pod Test (DPT-SM).  Means were separated using the general linear model (GLM) and ranked using the Student Newman-Keuls multiple comparison test (SNK).  ANOVA showed a significant difference at P=0.01 on tolerance between hybrids and P=0.001 on tolerance between hybrids and clonal groups. 40% of the hybrids tested were more tolerant than all the clonal groups.  The IMC clonal group was the most tolerant of the six clonal groups tested and ranked third overall between hybrids and clonal groups tested. Although the tolerance score varied between hybrids of clones PA107*SNK614 was the most tolerant (0.79) and T75/501*SNK 64 being least tolerant (2.00), all of these hybrids of clones possesses real potential to the tolerant to the black pod disease.