Abstract
In this study we evaluated the antagonism in vitro of Trichoderma harzianum strain VSL291 against 18 pathogens of cocoa fruits in dual culture. T. harzianum VSL291 inhibited the growth of the phytopathogenic fungi tested between 10.54 and 85.43%. The mycoparasitism of Moniliophthora roreri by T. harzianum VSL291 was studiedby light and scanning electron microscopy. T. harzianum VSL291 hyphae grew in parallel with the hyphae of M. roreri and in some places these were united with the hyphae of the cocoa pathogen through small structures like apresorious that tangled in the pathogenic fungus preventing its growth. T. harzianum VSL291 produced lytic enzymes: β-1,3-glucanases, chitinases, proteases, xylanases and lipases, when grown in minimal medium, with fungal cell walls as the sole carbon source. The highest proteolytic activities detected in T. harzianum VSL291 broth with M. roreri, Penicillium expansum and Byssochlamys spectabilis cell walls appear to be associated with increased activities of b-1,3 glucanases, chitinases, lipases, proteases and xylanases and biocontrol index derived from the experiments of confrontation. These results suggest that proteolytic enzymes according to their degree of induction could participate in the antagonistic effect ofT. harzianum VSL291 against the fungi tested. Key words: Antagonism, Trichoderma harzianum, mycoparasitism, phytopathogenic fungi
Highlights
In the year 2010, the world wide cocoa was estimated in 3.7 millions of ton, of which Africa was the main producer with 2.51 millions of ton, Asia and Oceania 0.66 millions of ton and Latin America and the Caribbean with 0.51 millions of ton (FAO, 2004)
T. harzianum VSL291 hyphae grew in parallel with the hyphae of M. roreri and in some places these were united with the hyphae of the cocoa pathogen through small structures like apresorious that tangled in the pathogenic fungus preventing its growth
The highest proteolytic activities detected in T. harzianum VSL291 broth with M. roreri, Penicillium expansum and Byssochlamys spectabilis cell walls appear to be associated with increased activities of -1,3 glucanases, chitinases, lipases, proteases and xylanases and biocontrol index derived from the experiments of confrontation
Summary
In the year 2010, the world wide cocoa was estimated in 3.7 millions of ton, of which Africa was the main producer with 2.51 millions of ton, Asia and Oceania 0.66 millions of ton and Latin America and the Caribbean with 0.51 millions of ton (FAO, 2004). In cocoa plantations a lot of wastes are made that generally remains scattered into the plantation and causing the Abbreviations: BCI, Biocontrol index; PDA, potato dextrose agar; SD, standard deviation phytopathogen fungi propagation that affect the cacao plant and play an important role in the destruction of the important natural resources of the cocoa industry. The worldwide cocoa production was seriously affected by diseases caused by phytopathogenic fungi. Diseases caused by Phytophthora strains produce cocoa losses worldwide between 45 to 100% of the production (Djocgoue et al, 2010). The cocoa plants cultivated in the Chontalpa sub region located in the state of Tabasco, Mexico, are
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