Efficacy of potential bio-control agents isolated from Papaya rhizosphere and new generation fungicides against root rot of Papaya incited by Fusarium solani (Mart.) Sacc.
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Date
2023
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RPCAU, Pusa
Abstract
Papaya (Carica Papaya L.) the versatile tropical fruit is a globally important crop which supports livelihood of millions of people. India is ranked first in production of Papaya and Bihar is ranked fourteenth among major Papaya producing states.Root rot incited by a soil borne fungi i.e. Fusarium solani is one of the most devastating disease of Papaya since last decade. This disease of Papaya has emerged as a serious threat for the Papaya crop cultivation in Bihar’s agro-climatic condition. The disease needs immediate attention as 90-95 per cent crop failure has been reported and mostly all existing varieties of Papaya are highly susceptible to this disease. Disease can only be managed effectively by use of resistant varieties which are scanty at present. Due to soil borne nature of pathogen, chemical and cultural methods are also not effective. Hence biological control is only plausible and explorable approach. Hence, this study was aimed to isolate microflora from rhizosphere of Papaya plants to evaluate their antagonistic potential against Fusarium solani causing root rot.
Among total 38 isolates obtained from Papaya rhizosphere 07 isolates were selected on basis of their promising antagonistic potential against Fusarium solani. The selected isolates showed Percent inhibition as follows: RB-13(79.59%), RB-15(80.70%), RB-24 (83.95%), RB-32 (86.48%), RB-25(89.30%), RB-29, (91.00%) and RB-34(93.85%).
Preliminary identification based on Gram reaction and KOH test, revealed that RB-13, RB-15, RB-24, RB-25, RB-29, RB-32 were gram positive and RB-34 was gram negative bacterial isolates. Furthermore, qualitative study of biochemical characters revealed that among 07 isolates, RB-32 was positive for catalase test, NH3 production and Siderophore production whereas none of the isolates were found to be producing HCN.
Out of these 07 isolates, further screening was done and 04 isolates exhibiting more than 85% Percent inhibition were selected. These isolates RB-25, RB-29, RB-32 and RB-34 were molecularly identified as Bacillus cereus (Bacterium te30A), Bacillus subtilis, Alcaligenes sp. and Bacillus velezensis respectively. All these bacterial biocontrol agents were first time isolated from Papaya rhizosphere and tested against Fusarium solani (Root rot disease causing pathogen).
In vitro evaluation of ten new generation fungicides at 50,100,150,250, and 500 ppm against Fusarium solani. Metalaxyl + Mancozeb was found most effective @100 ppm exhibiting inhibition percent of 93.41% followed by Tebuconazole @ 91.18 as compared to check. Moreover, Fosetyl-Al @ 100ppm was found least effective among all fungicides showing the inhibition percent of 25.92%.