Phylogeography of the witches'broom pathogen in Bahia. In: Agrotrópica v. 17 p. 65-72, 2005.

Abstract

Witches’ broom disease of cacao (Theobroma cacao L.), caused by Crinipellis perniciosa (Stahel) Singer, is the most important disease of cacao in the growing areas of South America and Caribbean Islands. Knowledge of the amount and distribution of the genetic variation within and among populations is important to understand the biology of this pathogenic fungus. Random amplified polymorphic DNA (RAPD) markers were used to determine the genetic structure of Bahian populations of C. perniciosa. Fungal isolates were collected by hierarchical sampling, from nine naturally infected cacao plantations, in three different agroecological zones, during a single growing season. Samples were collected from diseased pods and vegetative brooms in three trees per site. A total of 52 isolates were sampled. Trees were at least 10 m apart within an agroecological zone, and plantations at least 5 km apart each other. Spatial scales included comparisons within and among trees, within and among fields and within and among agroecological zones. Fungal populations from different zones differed significantly among themselves (p=0.1%). These result is in agreement with the previously reported degree of somatic compatibility groups in the C. perniciosa population from different ecological areas, which suggests that the fungal population infecting cacao plantations has different population structures in the the agroecological zones studied. Therefore, this result should be considered when devising strategies for controlling witches´ broom, including genetics, chemical and biological control.