Anatomical modifications in two cacao genotypes infected by Crinipellis perniciosa. In: Agrotrópica v. 10 p. 199-202, 1998.

Abstract

Crinipellis perniciosa, causal agent of Theobroma cacao witches' broom, infects regions of vegetative andlor reproductive growth promoting physiologic and anatomical modifications resulting in a 70-90% yield decrease. Its life cycle is constituted of two different morpho-physiological phases, one parasitic and intercellular and other saprophytic and intracellular. Two genotypes were used to study the anatomical modifications caused by the pathogen during the infection process, the hybrid SCA6 x Catongo and the open pollinated variety Catongo, tolerant and susceptible to witches' broom, respectively. The plants were inoculated, 20 days after emergence, with a mixture of isolates of C. perniciosa at a concentration of 2 x 10' basidiospores/cm3'. During the fungus parasitic phase, 30 days after inoculation, the infected plants showed absence of starch in the parenchyma cells associated with the medulla and vascular bundles and hypertrophy of xylem cells . ln contrast, healthy plants of those genotypes presented a great amounl of starch grains, mainly in the stem medulla of SCA-6 x Catongo and no hypertrophy of xylem cells. The results suggest that the variation in starch concentration in the studied genotypes may be associated with its degree of tolerance to witches' broom.