Postharvest Control of Litchi Fruit Rot by Bacillus subtilis

The litchi (Litchi chinensis Sonn.) fruit are extremely susceptible to postharvest moulds. The main pathogen of litchi fruit was isolated and identified as Peronophythora litchi. Of antagonists tested, Bacillus subtilis was the most effective against Peronophythora litchi. The relative antifungal activity of Bacillus subtilis reached a maximum after 48 h culture, and then decreased gradually. Purification of the crude extract of Bacillus subtilis followed by a Sepharose Toyopearl HW-50 gel filtration confirmed that the antifungal compound of Bacillus subtilis had a molecular weight of about 1.2 kD. Both the antagonist and its extract were effective in controlling artificially wound-inoculated fruit pathogens, but the use of the extract had better effect than that of the antagonist. Furthermore, application of the extract of Bacillus subtilis exhibited good control of decay for a storage period of 30 days at 5 °C and quality maintenance of litchi fruit in terms of eating scores and contents of total soluble solids, titratable acidity and ascorbic acid. No off-flavor of the treated fruit was tasted.