DEVELOPMENT OF EFFECTIVE BIOFORMULATION AND OPTIMIZED DELIVERY SYSTEM OF EFFICIENT NATIVE PLANT GROWTH PROMOTING RHIZOBACTERIA AGAINST SOILBORNE DISEASES OF TOMATO AND BRINJAL
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Date
2025-01-03
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Department of Plant Pathology, Bidhan Chandra KrishiViswavidyalaya, Mohanpur, Nadia – 741252
Abstract
Chitinolytic enzymes are known for their ability to degrade fungal cell wall and
are important in biocontrol of plant pathogens. Hence, chitonyltic microbes are gaining
meticulous attention for the management of phytopathogenic fungi. Further, there is a
need to develop suitable media to enhance the production of chitinase in cost effective
manner. In this work, cheap and readily available nutrient sources like sugarcane
molasses, vermicompost, neem cake, groundnut cake, Baker’s yeast and shrimp shell
chitin were used for the media optimization of potential chitinase producing biocontrol
agent of Pseudomonas aeruginosa GP8. Concentration of various cheap and readily
available carbon and nitrogen sources supporting significantly high bacterial population
and chitinase activity were selected and ten rudimentary media were made by combining
these nutrient. Various media screening parameters, viz., CFU count of P. aeruginosa
GP8, chitinase activity and zone of inhibition against S. rolfsii were recorded and rank
analysis was performed. Based on the cumulative rank of these four factors, overall rank
was calculated and three media i.e., VMYC, MGYC and NMYC were selected for
optimization. Response surface methodology and central composite design was employed
to optimize the variables for maximum chitinase activity. In VMYC, linear model was
accepted over quadratic model as difference between the adjusted R2 and predicted R2
was less in the linear model (adjusted R2= 0.8604 and predicted R2 = 0.8593) than the
quadratic model (adjusted R2= 0.7913 and predicted R2 = 0.7840). However, quadratic
model was selected in case of MGYC and NMYC.
The best optimization observed for VMYC was vermicompost = 250 g/L; SM= 150 g/L;
Baker’s yeast extract= 2.5 g/L and purified chitin = 0.5 g/L providing chitinase activity of
2.014 EU/ml. The final composition of the optimized MGYC media was sugarcane
molasses =10 g/L, groundnut = 200 g/L, Baker’s yeast = 2.5g/L and chitin powder = 5
g/L providing maximum chitinase activity of 3.000 EU/ml. In the case of NMYC, the
combination of neem cake = 199.52 g/L, sugarcane molasses =149.03 g/L, Baker’s yeast
= 0.15 g/L, and chitin powder = 4.97 g/L showed highest chitinase activity of 2.264
EU/ml. Validation of optimization result indicated Model 2 as the best fit model for
MGYC with highest mean prediction accuracy of 95.79 % and RMSE value of 0.057
followed by model 3 for NMYC (mean prediction accuracy of 95.61%, RMSE of 0.050)
and model 1 for VMYC (mean prediction accuracy of 93.15%, RMSE of 0.077). The
optimized media showed strong antifungal activity against Sclerotium rolfsii, and
Fusarium spp. resulting in 65.19 % and 56.30 % reduction in pathogen’s mycelial growth
over the control. Scanning electron micrographs showed mycelial deformation in the
zone of interaction of GP8 and the pathogenic fungi S. rolfsii and R. solani. Moreover, an
increase in secondary metabolites production was found in this optimized media. The cost
of preparation of 10 L of media for NB was Rs. 375.95, Rs. 115.5 for VMYC, Rs. 155 for
MGYC and Rs. 312 for NMYC. Thus, cost analysis depicts that the media cost is three
times and two times less than the nutrient broth for VMYC and MGYC media,
respectively. Pseudomonas aeruginosa GP8 was grown in MGYC, VMYC, NMYC and
NB media for preparation of talc and two liquid formulations (liquid-1 and liquid-2).
These formulations showed superior rhizospheric colonization ability in tomato seeds and
bacterial population of above 108 log CFU/ml was maintained for all the formulations.
Evaluation of in vitro antagonistic potentiality of encapsulated bacteria against
Sclerotium rolfsii, Rhizoctonia solani and Fusarium sp. showed 10.62%, 4.63% and
17.65% increase in antagonistic activity (%) compared to non-encapsulated bacteria,
respectively. The different bioformulations were applied to tomato and brinjal under field
conditions as Soil treatment + Seedling root dip+ Soil drenching to study their effect on
plant growth and biotic stress management. All the bioformulations improved plant
height and yield significantly compared to NB formulation and reduced southern blight of
tomato and collar rot of brinjal incited by S. rolfsii. However, field experiment on tomato
and brinjal indicates T3 (Talc formulation from MGYC) as the superior formulation
followed by T7 (Liquid-1 from MGYC) and T2 (Talc formulation from VMYC)
considering plant height, yield and disease reduction.