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POSTERS: Analytical and theoretical plant pathology

Phytophthora canker affecting CCN51 clones on high productivity cacao farms in Ecuador
Alina Puig - USDA-ARS. Carmen Suarez-Capello- Mars Inc., Osman Gutierrez- USDA, Jean-Philippe Marelli- MARS/USDA Cocoa Laboratory

Phytophthora spp. cause the greatest losses in cacao (est. 800K MT/year), producing disease on both pods and stems. Management practices and site characteristics influence disease development by affecting pathogen growth and survival. In Ecuador, high levels of canker disease were reported on CCN51, a widely planted clone. However, the epidemiology of canker infection in the field is poorly understood. The objective of this study was to identify variables affecting canker development and establish a baseline for incidence on commercial farms. Data on productivity and disease incidence were collected every 2-3 weeks, on 25 randomly selected trees on each of the 12 plots. The pathogen was isolated from stem and fruit lesions and identified as Phytophthora palmivora based on ITS and COX1 sequences.

Canker incidence ranged from 0 to 28% of trees, with more infections observed during the dry season (Jun-Aug). Cankers reach up to 2 m in vertical length but do not cause mortality. No canker was observed on trees of the Nacional background genotype, supporting the hypothesis that CCN51 is relatively more susceptible. Pod infection was greatest from Jan-Mar, with 1.2-6.9% of pods infected per tree. No relationship was found between pod infection and canker. In addition, planting density did not appear to affect disease development, with the most densely planted lot (1800 plants/ha) having the lowest incidences of pod rot and canker. In addition to providing valuable baseline disease data for CCN51 in South America, this study identifies contributing factors for canker development.