Isolation and evaluation of potential biological control agents of theobroma cacao (cacao) against vascular streak dieback disease (VSD)

• Main Author: Muñoz, Frances Luisa A.
• Format: text
• Language: English
• Published: Animo Repository 2017
• Subjects: Agricultural pests Biological control; Cacao > Diseases and pests; Plant diseases
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/5635
• Institution: De La Salle University

Theobroma cacao, or cacao, serves as the main ingredient for chocolates all around the world. Not only that it is the ultimate source of chocolates but its by products were proven to have their potential uses. Our country is recently being regarded as one of the major sources of cacao which can help solve the worldwide problem of inadequacy in cacao production. However, several diseases have caused a major decline in the production of this very important crop in the Philippines. Vascular Streak Dieback disease or VSD has been fast-spreading and affecting the population of cacao trees in Davao City, Philippines. The causal pathogen of the disease was isolated and identified as Lasiodiplodia theobromae (Alvindia and Gallema, 2017). A total of 39 isolates were enumerated and most effective isolates to inhibit the growth of the pathogen were considered as potential biological control agents (BCAs). Potential BCAs were identified as Trichoderma asperellum, Trichoderma longibrachiatum, and two species of the genus Bacillus, which has a 100% bootstrap value suggesting that these two isolates may be belonging to the same taxon, i.e. Bacillus cereus. These BCAs were tested in vitro, through dual incubation method and in vivo, via seedling trial. DGA02 (Trichoderma harzianum) and DGA14 (Bacillus amyloliquefaciens) were also included in the trials. Results revealed that spore suspensions of T. asperellum, Bacillus sp. and DGA02, administered through manual spraying, were the most effective treatments for artificially infected cacao seedlings. Effectivity of these isolates was manifested by the results which yield high leaf green index as well as low chlorotic leaf index among treated seedlings.