Evaluation of microbial Bioherbicides for Eichhornia crassipes to rejuvenate water bodies of Punjab

Abstract

The present study was oriented to develop microbial bioherbicides for controlling the infestation of water hyacinth (Eichhornia crassipes) in the internationally acclaimed manmade wetland, Harike in Punjab, India. The idea was to develop a mycoherbicide using augmentative/ innundative approach for which mycoflora inhabiting the diseased Eichhornia from the wetland were recovered by using standard mycopathological techniques. Of the 52 isolates, only 9 isolates exhibited significant pathogenicity by assessment of their spore suspension (1x 106 spores/ml) using in vitro detached leaf bioassay. However, only two isolates #8BJSSL and #19BJSSL exhibited complete leaf area damage after 168 hpi and disease development in terms of AUDPC. On further evaluation of these spores on whole plants, #19BJSSL exhibited higher pathogenicity. Using morphological and molecular techniques these were identified as Phaeoacremonium italicum (#8BJSSL) and Diplodia mutila (#19BJSSL). This is the first report of occurrence of these fungi as pathogens of Eichhornia crassipes in the world. Further, culture filtrates of #19BJSSL and #8BJSSL were evaluated for their phytotoxic potential by in vitro leaf puncher assays wherein #19BJSSL exhibited significantly higher phytotoxicity. Hence culture filtrate of #19BJSSL was further extracted using organic solvents by liquid- liquid extraction procedure and again assessed for their phytotoxic potential using in vitro leaf puncher assay. The best phytotoxicity was exhibited by the hexane fraction. However, in the whole plant assays of culture filtrate, hexane and chloroform fraction of #19BJSSL, the culture filtrate exhibited the highest phytotoxicity followed by the hexane fraction and chloroform fraction. The highest phytotoxicity of the culture filtrate is attributed to synergistic effect of Alkaloids and terpenoids which present in different concentration in hexane and chloroform fraction affecting the phytotoxic activity.