ISOLATION OF Pseudomonas fluorescens AND PINK PIGMENTED FACULTATIVE METHYLOTROPHS FOR MANAGEMENT OF URDBEAN FUNGAL FOLIAR DISEASES
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Date
2023-12-26
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Acharya N G Ranga Agricultural University
Abstract
A total of 40 isolates, 20 of Pseudomonas fluorescens and 20 methylotrophic
bacteria were isolated from the blackgram phyllosphere and their biochemical studies
revealed that all the P. fluorescens isolates tested to be positive for Catalase, Amylase,
Urease and Protease activity. 17 out of 20 isolates had Siderophore production and only
two isolates has HCN production. Only one isolate had shown positive for indole
production. All the PPFM isolates were found positive for Catalase and Urease activity
and negative for HCN production. Fourteen out of 20 PPFM isolates had shown
Amylase activity, only one isolate shown positive for Protease activity and two had
shown positive for Siderophore production.
Testing for PGP traits revealed that 15 P. fluorescens isolates had shown Psolubilization,
six isolate had shown IAA production and five isolates had shown Ksolubilization.
Eleven PPFM isolates had shown positive for P- solubilization and only
one isolate had shown positive fir IAA production and all the PPFM isolates had shown
negative for K- solubilization.
In vitro dual culture studies revealed that, among 20 P. fluorescens isolates
tested, two isolates viz., CBP- 05 and PPP-01 were found to be the most promising
isolates with maximum antagonistic potential against Corynespora cassiicola (66.51%
and 64.99%) and Alternaria alternata (60.43% and 60.43%). Two methylotroph
isolates viz., PPM-01 and ABM-04 exhibited maximum antagonistic potential against
C. cassiicola (68.04% and 54.34%) and A. alternata (34.55% and 34.55%).
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Intra and inter compatibility studies of four antagonistic bacterial isolates, viz.,
two Pseudomonas (CBP-05, PPP-01) and two methylotrophs (PPM-01 and ABM-04)
revealed that all the isolates were compatible with each other under in vitro conditions
which was tested through cross streak method.
Based on 16S rRNA gene sequencing the Pseudomonas isolate PPP-01 and
CBP-05 was found closely related with Pseudomonas fluorescens. However, the
methylotroph PPM-01 grouped with Methylobacterium indicum and ABM-04 grouped
with Hyphomicrobium facile. The pathogens Corynespora grouped with Corynespora
cassiicola isolate while Alternaria was related with Alternaria alternata isolate.
Under field conditions, Fungicidal check had shown lowest PDI and AUDPC
against Corynespora leaf spot (28.11% and 501.10 respectively) and Powdery mildew
(0.00% and 0.02 respectively) and there was a significant increase in yield (1130.40 kg
ha-1), number of pods per plant (20.10), no. of seeds per pod (5.63) and test weight of
3.85g.
Among the antagonist treated plots, foliar spray of consortium of CBP-05, PPP-
01, PPP-01 and ABM-04 @ 108 CFU ml-1 has recorded the lowest PDI against
Corynespora leaf spot (36.37%) and Powdery mildew (38.17%) and minimum area
under disease progress curve for both Corynespora leaf spot (639.03) and Powdery
mildew (644.33). It was also observed to significantly increase the number of pods per
plant (19.50), No. of seeds per pod (5.43) and the highest test weight of 3.77g, yield of
1080.25 kg ha-1.
However, the benefit cost ratio (BCR) of the different treatments varied from
0.99 to 1.70 with the highest BC ratio was recorded with Treatment T7 (CBP-05, PPP-
01, PPP-01 and ABM-04 (FS)) (1.70) and the fungicide treatment having BC ratio of
1.55 which represents, the combination treatment is a potential alternative to fungicides