Reaction to moniliophthora roreri in theobroma spp. At caquetá, colombia

Abstract

The aim of this study was to evaluate in situ the reaction of 50 genetic materials of three species of Theobroma (T. cacao, T. grandiflorum and T. bicolor) to controlled inoculation of three autochthonous isolates of Moniliophtora roreri (the causal agent of moniliasis or frosty pod disease), at the Department of Caquetá (Colombian Amazonia). The variables disease incidence (IMr), external severity (SE), and internal severity (SI) were evaluated at nine weeks after inoculation of 2-to-3-month-old fruits with a spore suspension of 1.2 × 105 spores/mL. The disease was evidenced in the three species of Theobroma; however, 13 of the 50 genetic materials did not present symptoms, well represented by: six T. grandiflorum, five T. bicolor and two T. cacao. The genotypes of T. bicolor and T. grandiflorum were the least affected, compared to those of T. cacao. There were significant differences for IMr, SE and SI among the three species of Theobroma and among the 50 genetic materials. Significant differences among the isolates were found only for SE. The disease incidence and severity among materials were influenced by the used inoculum. Genotypes with less reaction to M. roreri can be used in breeding programs for the resistance to moniliasis.