The use of Bacillus subtilis and Debaromyces hansenii in controlling postharvest decay of sweet orange fruits

Abstract

Bacillus subtilis and Debaromyces hansenii isolated from fruit washings of sweet oranges that did not decay after four weeks of bulk storage were tested for antagonism towards three rot fungi of oranges namely: Aspergillus niger, Botryodiplodia theobromae  and  Penicillium italicum.  Spore suspension (approx. 105 spores/ml) of each rot fumgus was introduced into wound sites on oranges before, simultaneously or after inoculation of cell suspension (5.2 x 107 cfu/ml) of B. subtilis  or D. hansenii.  The two microbes significantly (P < 0.05) reduced the number of wound sites developing infections.  The antagonists were more effective when applied before than after inoculation of pathogen.  The antagonists significantly (P < 0.05) reduced the rate of natural infection of sweet orange fruits over a three weeks storage period, and their efficacy was comparable to that of fungicide (Tecto) treatment.  The efficacy of B. subtilis  in controlling postharvest rot of sweet orange fruits was higher than that of D. hansenii.