Comparative Assessment of the Resistance of Cocoa (Theobroma cacao L.) Progenies from SNK10 x SNK413; ICS84 x ICS95 to Phytophthora megakarya in Cameroon by Measuring Size of Necrotic Lesion along the Midrib

The susceptibility of Theobroma cacao L. to Phytophthora megakarya was assessed in four seedlings progenies (& ICS84 H % ICS95, & ISC95 H % ICS84, & SNK413 H % SNK10, & SNK10 H % SNK413) by measuring daily, the size of the necrotic lesion along the midrib after Inoculation. Using the statistical analysis of necrotic lesion along the midrib it was possible to show that progenies resulting from three clustured in 12 and 14 groups. The sizes of the lesion of parental clones are significantly different. The values of heterosis allow confirm the transmission of the vigor to the hybrid. For each progeny, more than 60% of individuals show this phenomenon. The ANOVA analysis of necrotic lesion shows a significant effect of day after inoculation and genotype to all the progenies at 0.001 probability level. Narrow sense heritability was average for SNK clones (local Trinitario) and high for ICS clones (introduced Trinatario), varying between 0.43 and 0.73. This suggested that ICS clones appeared to be the best promising parents than SNK. For every reciprocal crossing, no significant difference of narrow sense heritability was observed, this suggested the absence of a maternal effect when considering the size of necrosis.