Abstract
Phytopathogenic fungi, Phytophthora palmivora and Phytophthora megakarya continue to be a major threat to cocoa production worldwide. To counter these drawbacks, producers rely heavily on agrochemicals leading to pathogen resistance and environmental hazards. There is also increasing demand by cocoa consumers for pesticide-free seeds. Therefore, biological control through the use of natural microbial antagonists is more rational and safer crop management option. The plant-associated Bacillus amyloliquefaciens, ESI was selected in vitro, among seven other Bacillus species as the most promising, using the zone of inhibition techniques. The B. amyloliquefaciens together with two other laboratory contaminants, Aspergillus and Penicillium spp. were used to control black pod disease of cocoa caused by P. palmivora and P. megakarya on detached cocoa pods and under field conditions. Even though all the eight bacterial isolates inhibited the black pod fungi in vitro, B. amyloliquefaciens, ESI inhibited P. palmivora with the highest inhibition zone of 21.21 mm and P. megakarya with 16.00 mm. The Aspergillus and Penicillium spp. also inhibited P. palmivora with an inhibition zone of 22.41 and 16.81 mm, respectively. Detached cocoa pod areas protected with broth suspensions of the three microbial antagonists and challenged with a zoospore suspension of P. palmivora, completely prevented black pod lesion development. Field pods sprayed with individual microbial broth suspensions and their mixtures and also challenged with a zoospore suspension inoculum, controlled black pod disease with percentage disease control ranging from 53.33-66.67% in the minor season and 40.00-66.67% in the major season. Results clearly show that these antagonists have the potential to be developed as biocontrol agents for the management of black pod disease of cocoa. Key words: Biocontrol agents, pathogenic fungi, microbial antagonists, inoculum, Bacillus amyloliquefaciens, Aspergillus sp. and Penicillium sp.
Highlights
Phytopathogenic fungi are a threat to cocoa (Theobroma cacao L.) production worldwide as they are the major causes of crops losses
All eight rhizobacterial isolates screened showed some level of activity towards both P. palmivora and P. megakarya after 12 years of refrigerated storage (Table 1)
When the rhizobacteria were re-tested against P. palmivora in comparison with the two fungi viz., the Aspergillus and Penicillium spp., all eight rhizobacteria
Summary
Phytopathogenic fungi are a threat to cocoa (Theobroma cacao L.) production worldwide as they are the major causes of crops losses. This has had a serious economic impact on cocoa production, over the last few. To counter these drawbacks, farmers have relied heavily on agrochemicals, basically copper-based fungicides. Biological control through the use of natural antagonists such as rhizosphere-associated bacteria as biocontrol agents and stimulating plant growth has emerged as promising alternatives to chemical pesticides for more rational use and safe crop management (Lucy et al, 2004; Somers et al, 2004; Lugtenberg and Kamilova, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
