EFFECT OF CO-INOCULATION OF PLANT GROWTH PROMOTING RHIZOBACTERIA AND CHEMICAL FERTILIZERS ON RHIZOBACTERIAL COMMUNITY STRUCTURE AND FUNCTION OF TOMATO (Solanum lycopersicum L.)
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Date
2017-09
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UHF,NAUNI
Abstract
ABSTRACT
Plant growth promoting rhizobacteria are the soil bacteria inhabiting around/on the root surface and are
directly or indirectly involved in promoting plant growth and development via production and secretion of
various regulatory chemicals in the vicinity of rhizosphere. Generally, plant growth promoting rhizobacteria
facilitate the plant growth directly by either assisting in resource acquisition (nitrogen, phosphorus and essential
minerals) or modulating plant hormone levels or indirectly by decreasing the inhibitory effects of various
pathogens on plant growth and development in the forms of biocontrol agents. The plant-beneficial rhizobacteria
may decrease the global dependence on hazardous agricultural chemicals which destabilize the agro-ecosystems.
PGPR are commonly used as inoculants for improving the growth and yield of various agricultural crops.
Beneficial effects by introduction of specific microorganisms as PGPR on plant growth have been reported for
numerous vegetable crops including tomato, capsicum, cauliflower and other crops grown under field conditions
In the present study, PGPR (Bacillus subtilis strain 21), isolated from tomato crop with wide range of PGP
traits viz., phosphate solubilization, siderophore production, HCN and IAA production was used as an inoculant
to study its efficacy on growth and yield of tomato under field conditions (at variable concentration of chemical
fertilizers). The PGPR Bacillus subtilis inoculation with 100% NPK showed significant increase in various
growth parameters viz root length (50.94 %), shoot length (22.9 %), plant biomass (92.37 %), number of fruits
per plant (61.02 %), average fruit weight (12.04 %), yield (88.61 %), ascorbic acid content (41.63 %) and TSS
content (12.8 %) over control was recorded. Inoculation with PGPR enhances resident bacterial community and
hence showed significant increase in bacterial population associated with tomato rhizosphere and
endorhizosphere. A total of sixty five bacterial isolates were screened for P-solubilization, antifungal activity,
HCN, siderophore and IAA production. On the basis of these activities, thirty one bacterial isolates were
analysed for genetic diversity of ARDRA analysis. All the isolates were grouped into three major phylotypes at
75 % similarity level. The representative bacterial isolates from each phylotype were identified by 16S rDNA
sequencing and identified species were Acinetobacter calcoaceticus, Pseudomonas sp., Pseudomonas
aeruginosa, Serratia marcescens, Enterobacter sp. and Bacillus sp. Thus, the results of this study provides
comprehensive information on the ability of Bacillus subtilis strain S21 significantly enhance the plant growth
promotion of tomato when supplemented with chemical fertilizers and diversity analysis of resident
rhizobacterial community.
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