EFFECTS OF SECONDARY METABOLITES STATUS OF BACILLUS SPP. ON FUNGAL PATHOGEN ALTERNARIA ALTERNATAT. ANGAYARKANNI AND ANITHA SUBASH
Alternaria diseases are among the most common diseases of many plants throughout the world. They affect primarily the leaves, stems, flowers and fruits of annual plants, especially vegetables and ornamentals. In this study the in vitro screening of antagonistic Bacillus spp. against Alternaria alternata revealed that the maximum inhibitory effect on the mycelial growth was exhibited by the isolates AUB4 and AUB3. Maximum siderophore production was observed in the isolate AUB7. Estimation of salicylic acid production by the Bacillus spp. isolates showed that isolate AUB4 produced maximum amount. Crude extract of Bacillus antibiotics showed that isolates AUB6, AUB4, AUB2 and AUB1 have maximum inhibitory effect on the mycelial growth of Alternaria alternata. The TLC analysis of antibiotics extracted from isolates AUB7 and AUB4 showed Rf values of 0.63 and 0.69 for surfactin and 0.48 and 0.53 for iturin A respectively. Thus, from the present study, it can be concluded that among the several secondary metabolites produced by the Bacillus spp isolates, siderophores, salicylic acid and antibiotics are significantly involved in the suppression of the growth of Alternaria alternata. Among the ten isolates screened, AUB4 and AUB7 effectively controlled the growth of the fungal pathogens. This may be due to the high production of siderophore, salicylic acid and antibiotics like surfactin and iturin.
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