Abstract
Abstract
Black pod disease is a major threat to global cacao (
Theobroma cacao
L.) production. It is caused by multiple
Phytophthora
species with geographic ranges from regionally restricted to pantropical, and developing resistant cultivars requires screening against the diversity of these pathogens. This study evaluated the response of 25 cacao clones to 13 isolates of
P. palmivora
(eight),
P. megakarya
(two), and
P. theobromicola
(three) by nonwounding inoculation of detached pods. Lesion size and lesion expansion status were evaluated 4 days after inoculation. The linear mixed model included 178 combinations among 17 clones and 12 isolates, each represented by at least two biological replicate pods. Lesion size differed among clones (F
(16, 449.2)
= 25.16) and among isolates (F
(11, 416.0)
= 32.90), and the clone by isolate interaction was significant (F
(150, 465.4)
= 1.72; all
P
P. megakarya
GH34. The probability of lesion expansion also differed among clones and isolates (both
P
< 0.001). Together, these findings identify candidates for further resistance evaluation and show that multi-isolate screening provides a stronger basis for selecting materials for black pod resistance breeding.