Tene Tayo Paul Martial; Ngotcho Esther Ngassam;
Streptomyces cameroonensis possesses antimicrobial and Plant growth Promoting activities. As freshly prepared cultures are not convenient for agricultural systems, a formulation better suited for storage, transport and ease of application becomes an important requisite for the biocontrol agent to be developed for commercial use. The aim of this study is to evaluate the efficacy of a bioformulation of S. cameroonensis for control of black pod disease and enhancement of seedling growth. The formulation was developed using a mixture of cassava starch/talc powder. The stability, texture, storage temperature and shelf life of the formulation were determined over a period of six months. The efficacy of the formulation was determined in vitro against Phytophthora megakarya. In planta assay performed on two hybrids of cocoa seedlings, the tolerant SNK413×T79/467 and the susceptible UPA134×SCA12 in the greenhouse was conducted to determine the efficacy of the formulation on growth and resistance of cocoa seedlings. The formulation showed high shelf-life after six months of storage at an optimal temperature of 4°C with 1.07 x 106 CFU/g. Inhibition of spore germination in Phytophthora megakarya showed 100% inhibition at 10% w/v of formulation. Detached leaf assay showed a significant reduction in the disease severity index of about 67% for the more tolerant hybrid and 55% for the susceptible hybrid. A significant enhancement in stem length, leaf surface area and root weight was observed. Analysis of the biochemical markers of defense showed a significant increase in total polyphenol content, flavonoid content and total protein content as well as up-regulation of PR-proteins such as Chitinase, peroxidases and β-1, 3-glucanases and polyphenoloxidase activities in plants treated with the formulation. The study demonstrated the stability and efficacy of the S. cameroonensis powder formulation in suppressing black pod disease in cocoa and subsequently enhancing the growth of seedlings.
Keywords: Streptomyces cameroonensis, bioformulation, cocoa, Phytophthora megakarya.