Reactions of cocoa (Theobroma cacao) seedlings and clonal plants to isolates of Crinipellis perniciosa in Trinidad

Abstract

Variability among isolates of Crinipellis perniciosa (Stabel) Singer in Trinidad was assessed to determine whether pathotypes of the fungus exist on the Island. Comparisons were made of morphological reactions caused by the isolates on cocoa seedlings from open and controlled pollinations and on clonal plants. The histopathological effects of the isolates were assessed on seedlings. Significant differences between some of the isolates on the open-pollinated progeny were not confirmed on the clonal plants. The morphological changes in SCA 6 progeny and the highly resistant reaction of clone SCA 6 indicated absence of pathotype A in Trinidad. It is concluded that only pathotype B exists on the Island. The implications of this finding for breeding programmes for resistance to witches' broom disease and quarantine regulations for cocoa are discussed.