Microbial Remediation of Pesticide Accumulation and its Response of Bacterial Wilt in Brinjal

Abstract

Growing brinjal (Solanum melongenaL.) in a soil polluted with organophosphorus pesticide (OP) residues coupled with an additional threat of wilt disease caused byRalstonia solanacearum(Rs), pose a formidable management challenge for residue free crop production. Our study aimed at identifying efficient OP-degrading bacteria (OPDB) and their compatibility with microbial bio-control agents (MBCA) for twin objective of microbial degradation of OP -residues and reduction in incidence of bacterial wilt of brinjal in OP-contaminated soil. As many, ten bacterial isolates showing OP-degrading potential were recovered through colony growth in mineral salt (MS) - medium treated with 25 ppm chlorpyriphos. Efficient isolates displaying growth up to 700ppm chlorpyriphos were further screened for OP-degradation, leading to identification of two most efficient OPDB,Acromobacter marplatensis[MW397524] (Am) andPseudomonas azotoformans[MW397525] (Pa). These two isolates havingin vitrocompatibility with each other, showed further compatibility with two most widely used MBCA, viz.,Pseudomonas flourescens[KT258013] (Pf) andTrichoderma harzianum[ON364138] (Th), facilitating the development of consortium having extended functional corridor. The response of combination of OPDB + MBCA(Am+Pa+Pf+Th) showed 80% lower percent wilt incidence (PWI), 2.8 times higher fruit yield of brinjal, and 15-25% lower OP-residues over un-inoculated control treatment. Our studies, hence, put forward a strong unified delivery mechanism of OPDB and MBCA as a part of green technology for chemical residue -free vegetable production in contaminated soils.IMPORTANCEMicrobes isolated from crop rhizospheres are known to exhibit multiple functions (plant growth promotion, antagonism against soil borne pathogens e.g.,Rs,and acaricidal properties) depending upon type of stimuli by regulating the plant defense. Considering the limited past efforts on twin objective of cleaning up the pesticide residues accumulated in the soil (microbial removal of pesticide residues) and providing an additional safeguard against soil borne pathogen causing bacterial wilt in brinjal to collectively develop a microbial consortia mediated crop production system, devoid of any chemical residues. Such an effort adds strength to organic production system on pesticide contaminated soils. In the present study, we succeeded in identifying two most effective chloropyrifos residues degrading OPDB having compatibility two MBCA for developing consortia formulation, which aided in developing pesticide residue free soil, neutralising bacterial wilt pathogen (Rs), and creating a better nutrient supply for a well deserved production system. Such efforts would pave the way for developing more robust microbial formulations (with emphasis on entomopathogenic application) having dynamic microbial functions to replace any futuristic use of agrochemcials.