Detection of genetic resistance to cocoa black pod disease caused by three Phytophthora species

Disease has become a major limiting factor for the production of cacao crops. Black pod disease, which is caused by Phytophthora spp., has caused losses of 40 % of the worldwide production of cacao crops. The most efficient way to control black pod disease is to use resistant crop varieties. In this study, a total of 262 genotypes obtained from F1 cacao segregating progeny (TSH 1188 × CCN 51) were evaluated for their genetic resistance to infection by three species of Phytophthora. The descriptive estimates of resistance were significant (p < 0.01), and a high level of heritability was observed for Phytophthora spp. (h2 = 0.759 for P. citrophthora, h2 = 0.839 for P. palmivora, h2 = 0.799 for P. capsici). Statistically distinct homogeneous groups (p < 0.01; Scott–Knott) were observed. Ten genotypes that are resistant to Phytophthora spp. were identified. The frequency of the individuals within each homogeneous group suggests that resistance to black pod disease is oligogenic. Our results, which suggest that resistance to black pod disease in cocoa trees is most likely oligogenic, have extremely important implications for cocoa breeding programs. Resistance to the various species that cause black pod disease in cocoa is associated with genetic variability. This result is very important for cocoa breeding programs that aim to use molecular markers to increase genetic selection gain per unit time. The genotypes of the cocoa progeny segregating in the F1 generation (TSH 1188 × CCN 51) are very useful in studies aimed at increasing cocoa resistance to black pod disease.