Study of antagonistic yeasts isolated from some natural sources of West Bengal

An intensive survey was conducted and 196 samples were collected from different zones of 12 districts of West Bengal. The collected samples were various fruits ( apple , green grapes . brown grapes , date fruits , jamun and fig ) ,juices ( date juice , toddy , cane juice ) and milk. From these samples 588 yeast colonies were isolated .These yeasts were identified by conventional morphological, microscopical and biochemical testing methods. These colonies comprise of 23 genera and 38 species of yeasts. Out of 38 isolated & identified species, 26 are ascomycetous while 12 are basidiomycetous yeasts .Maximum number of species were found in Candida (5) and followed by Pichia(4), Rhodotorula(3) and Saccharomyces (2).The percent of occurrence , Berger – Parker dominance index of each species were calculated. All yeast species isolated were screened by dual culture plate method for their antagonistic property against Penicillium digitatum, causal pathogen of Penicillium rot of Citrus . Out of 38 species of yeasts,15 species were antagonistic to Penicillium digitatum. Candida famata gave maximum percent of radial inhibition ( 70.24 PIRG)followed by Pichia membranifaciens (68.21PIRG) and Rhodotorula mucilaginosa (60.56 PIRG).Therefore , these natural sources of West Bengal are good habitats of various yeast species including antagonistic yeasts and the antagonistic yeasts can be applied as biological control agents against post harvest Penicillium rot disease of Citrus