|SRIWATI, RINA - Syiah Kuala University|
|MELNICK, R - Former ARS Employee|
|MUARIF, RIZKY - Syiah Kuala University|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2015
Publication Date: 10/1/2015
Citation: Sriwati, R., Melnick, R.L., Muarif, R., Strem, M.D., Samuels, G.J., Bailey, B.A. 2015. Biological control of Black Pod Disease and Seedling Blight of cacao caused by Phytophthora Species using Trichoderma from Aceh Sumatra. Biological Control. 89:33-41.
Interpretive Summary: Chocolate is produced from the seeds of the cacao tree. Black pod rot is a plant disease causing serious reductions in yield in Indonesia, a major cacao producing area. Black pod rot is caused by the plant pathogen Phytophthora. Beneficial fungi are being tested for their potential to reduced losses to black pod rot of cacao in Indonesia, a management tool know as biological disease control. Beneficial native fungi, species of Trichoderma, were isolated from cacao tissues in Indonesia and evaluated for their abilities to kill or slow the growth of the Phytophthora. One Trichoderma isolate was identified which attacked and delayed or destroyed Phytophthora using several mechanisms. When the Trichoderma was applied to cacao seedlings and fruits, it reduced the amount of disease caused by Phytophthora. The beneficial Trichoderma isolate identified has potential for use in managing black pod rot of cacao in the field in Indonesia. If successful, this new management tool would limit cacao disease losses, improving the lives of cacao farmers, and contribute to stabilization of cacao supplies available to the chocolate industry.
Technical Abstract: The cocoa tree, Theobroma cacao L., suffers large yield losses in Aceh Indonesia to the disease black pod rot, caused by Phytophthora spp. Despite having the largest area under cacao production in Sumatra, farmers in the Aceh region have low overall production because of losses to insect pests and black pod rot. Trichoderma spp. were isolated from the roots, leaves, and branches of cacao trees screened as potential biological control agents against black pod rot. Isolates used in the study were T. asperellum isolates T2 and T4, T. longibrachiatum isolates T15 and T16, and T. virens isolatesT1 and Tv. T1, T2, T4, and Tv completely colonized and destroyed Phytophthora mycelium in a pre-colonized plate assay. All six isolates reduced the growth of Phytophthora in a dual plate assay, with T1 causing the highest growth suppression. Growth of Phytophthora was suppressed when grown on MIN media amended with sterile heat inactivated Trichoderma culture filtrates, with Tv best suppressing growth at 59%. Tv was the only isolate observed coiling around Phytophthora mycelium. Additionally, Tv was the only isolate capable of reducing Phytophthora lesion expansion in a detached pod assay, reducing severity by 71%. T. virens isolate Tv also reduced Phytophthora seedling blight when applied to seedlings at 1x106 and 1x108 conidia/ml. T. virens isolate Tv is capable of using mycoparasitism, antagonism, and antibiosis against Phytophthora spp. likely contributing to its ability to limit black pod rot and seedling blight of cacao.