Abstract

DANIEL, Chanel K.; LENNOX, Cheryl L.  and  VRIES, Filicity A.. In-vitro effects of garlic extracts on pathogenic fungi Botrytis cinerea, Penicillium expansum and Neofabraea alba. S. Afr. j. sci. [online]. 2015, vol.111, n.7-8, pp.1-8. ISSN 1996-7489.  http://dx.doi.org/10.17159/SAJS.2015/20140240.

The antifungal activity of garlic extracts applied directly and through volatile release was tested against the growth of postharvest pathogens Botrytis cinerea, Penicillium expansum and Neofabraea alba. Mycelial growth of B. cinerea and P expansum was inhibited by aqueous and ethanol dilutions on garlic extract amended media (direct method) in a dose-response manner. The aqueous dilution was more effective than the ethanol dilution. Both dilutions inhibited mycelial growth of N. alba to a similar extent but no trend in data was noted across the concentration range. Calculated EC₅₀ values indicated that 13.36% and 8.09% aqueous dilutions could be used to inhibit growth of B. cinerea and P. expansum, respectively; however, values generated for N. alba either bordered on or exceeded the concentration range. The volatile vapour application of garlic was able to inhibit mycelial growth and spore germination of all pathogens at concentrations as low as 20%. Gas chromatography-mass spectrometry analysis showed that 85.95% of compounds present in the garlic sample belonged to a sulphur or sulphur-derived group. Allicin, the active component of garlic, was not found; however, breakdown products of allicin were present in high amounts. Overall, the antifungal activity of garlic extracts for the control of B. cinerea and P. expansum was confirmed. Further investigations into the antifungal effect of garlic extracts on N. alba is required, although garlic volatiles seem to be effective. This report is the first of antifungal activity of garlic extracts against N. alba - the causal agent of bull's eye rot, one of the major diseases of apples.

Keywords : plant extracts; antifungal activity; postharvest pathogens; sulphur compounds; volatiles.

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