Biocontrol potential of Trichoderma martiale against the black-pod disease ( Phytophthora palmivora) of cacao

Abstract

The Black-Pod Rot of cacao ( Theobroma cacao) caused by Phytophthora species is one of the most important diseases affecting this crop worldwide, with average annual losses above 30%. The aim of this work was to assess the potential for the endophytic Trichoderma martiale strain ALF 247 to control Phytophthora palmivora. When ALF 247 was applied at concentrations ranging from 1 × 10 4 to 5 × 10 7 conidia per milliliter, the disease severity decreased proportionally. Addition of vegetable oil and/or sucrose in the formulations did not affect the biocontrol results. Fungicides such as copper hydroxide and fosetyl-Al had no effect on conidial germination of this T. martiale strain, with the germination percentage maintained above 90%. Once sprayed, the population of T. martiale tended to decrease progressively on the surface of cacao pods (∼30–40 days post-application), with a concomitant increase in the severity of pod disease. Production of 1.02 × 10 8 conidia g −1 was obtained after culturing ALF 247 on solid substrate (rice grains) supplemented with calcium carbonate. The results indicate a clear-cut potential of the T. martiale ALF 247 to be used for control of Black-Pod Rot of cacao, although further studies are required to render this isolate technically and economically efficient as a biocontrol agent on agronomic scale.