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Title: Evaluation of microbial Bioherbicides for Eichhornia crassipes to rejuvenate water bodies of Punjab
Authors: Singh, Birinder Jit
Supervisor: Kumar, Maneek
Saxena, Sanjai
Keywords: Microbial;Eichhornia crassipes;Environment;Water bodies;Punjab;Rejuvenation;Bioherbicides;Harike
Issue Date: 20-Jul-2017
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. Using food poison assay the concentration of hexane fraction compatible to the spores of Diplodia mutila (#19BJSSL) was found to be 2.5 µg/ml which was used for preparation of a formulation with the spores for enhancement of the mycoherbicidal potential of Diplodia mutila for the control of E. crassipes. The bioherbicidal formulation (2.5 µg/ml hexane fraction+ 1x 106spores/ml) was found to induce the pathogenesis by 24 hours causing 13 % damage as compared to spores of wherein the initial symptoms of infestation occurred after 48 hours. Further, the bioherbicidal formulation exhibited 100% mortality of the test plants after 192hpt while the spore suspension only induced 84% death. Thus it was concluded that by use of crude phytotoxins with spores of Diplodia mutila there was a significant enhancement in the mortality of water hyacinth. Further the spores of Diplodia mutila were sprayed on non-target, economically important plants and duckweed. No disease development was observed in these plants till one month indicating the safety as well as suggesting the host specificity of Diplodia mutila (#19BJSSL) for Eichhornia crassipes. There was deterioration in the water quality of experimental tubs which is predominantly attributed to the dead and decaying biomass also enhancing the BOD, COD, TDS, Electrical conductivity, total coliforms and fecal coliforms. However there was a significant reduction in the evapotranspiration rate i.e. by 7% thus conserving water. Thus, from the present study it is concluded that #19BJSSL (Diplodia mutila) and its bioherbicidal formulation with crude phytotoxins offer a plausible alternative to control and manage the infestation of Eichhornia crassipes in Harike wetland. However, this method has to be integrated with the mechanical method for immediately removing the dead plant biomass, so as to prevent the deterioration of water quality thereby rejuvenating it.
Description: Ph. D Thesis
Appears in Collections:Doctoral Theses@CED

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