Abstract:
Fluorescent pseudomonads are an ecologically important group of rhizobacteria that are well accepted as biocontrol agent and plant growth promoter. Exploitation of such rhizobacteria for management of plant diseases reduces the hazardous effects of chemical to the environment as well as to human health. The present investigation was carried out with an aim to characterize the fluorescent pseudomonads predominant in mid and up hills of Meghalaya and to evaluate the antagonistic potentiality of native fluorescent pseudomonads against wilt pathogens of major vegetables in Meghalaya. A total of 72 rhizospheric soil samples were collected from different crop rhizospheres viz., maize, rice, banana, pea and pigeon pea from Ri-Bhoi (mid-hills) and East Khasi Hills (mid and up-hills) districts of Meghalaya. Fifty fluorescent pseudomonad isolates obtained from 72 collected soil samples were tentatively grouped into 4 categories i.e. Pseudomonas fluorescens bv. I and II; P. putida bv. A and B based on their cultural, morphological and biochemical properties. Isolates were further screened for production of HCN and presence of 2 biosynthetic genes for antibiotics viz., DAPG and pyrrolnitrin by using gene specific primer pairs Phl2a-Phl2b and Prncf-Prncr respectively. HCN production test was found positive for 12 isolates, whereas two and six numbers of isolates were recorded for presence of DAPG and pyrrolnitrin biosynthetic genes respectively. Antagonistic potential of 17 isolates positive for HCN and antibiotic production was tested against major wilt pathogens i.e. Fusarium oxysporum f.sp. pisi (pea) and Ralstonia solanacearum ( brinjal and capsicum) under in vitro conditions. The radial growth of F. oxysporum f.sp. pisi was found to inhibit most (3.23 cm) by isolate MRN 18, whereas isolate PC (17.33 mm and 15.67 mm) followed by USR 9.2 (16.00 mm and 15.00 mm) was found to have the highest inhibition zone against both R. solanacearum isolates from brinjal and capsicum. These two isolates must be further evaluated under in vivo condition for development of ecologically sustainable biocontrol strategy for management of wilt pathogens of vegetables.

Includes bibliographical references.