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Prospecting rice phyllosphere for microbial community engineering

KrishiKosh

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Title Prospecting rice phyllosphere for microbial community engineering
 
Creator SHOBIT THAPA
 
Contributor Radha Prasanna
 
Subject null
 
Description t-9778
Phyllosphere represents the critical biological interface between the above-ground
plant parts and the atmosphere, which influences growth, development and
productivity of crop plants. An investigation was undertaken to analyse the abundance
and functional attributes of the phyllosphere microbial communities in selected
cultivars of rice (Oryza sativa L.), as influenced by the methods of cultivation and
fertilizer application. In addition, native microflora with the biocontrol potential
against the fungal pathogen (Magnaporthe oryzae) were applied as the change-agents
for engineering desired phyllospheric microbial communities to inhibit the disease
progression.
Leaf samples of rice varieties from various agro-climatic zones of India were
analysed for the microbial abundance using both traditional and molecular methods.
The eubacterial load was highest, followed by those of cyanobacteria and archaea.
The rice cv. Pusa Basmati 1509 under the conventional flooding method without
chemical fertilizers supported higher microbial populations, including the guilds of Nfixers
and siderophore producers. But the application of recommended dose of
fertilizers (RDF) led to higher population densities of oligotrophs and P-solubilisers.
Majority of the isolates exhibited IAA and siderophore production with biocontrol
potential against phytopathogenic fungi. The group specific, polymerase chain
reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) analyses showed that
members of the phylum Proteobacteria were dominant, along with those of
Firmicutes and Planctomycetes in the phyllosphere. But their diversity and abundance
decreased due to RDF. Principal component analyses revealed a strong relationship
among the nutrient contents of leaves of seven rice cultivars tested and soils, and the
culturable phyllospheric microbial population.
The influence of N fertilization (0, 120 and 180N) on two susceptible (Pusa
Basmati 1 (PB-1) and CO-39) and resistant (Pusa 1609 and CO-39I) rice cultivars, to
the pathogen challenge (M. oryzae) and their interactive effects on the growth,
elicitation of defense/antioxidant machinery of plants, and the phyllosphere microbial
communities was evaluated. The analyses of the leaf microbiome using quantitative
real-time PCR (qPCR), revealed that the interaction of cultivars, disease challenge,
and N doses was significant at 1% level of probability for all the microbial
communities. The rice cv. CO-39 had higher copies of nifH genes while cv. Pusa
1609 had more of bacterial amoA. The promising phyllosphere isolates showing
biocontrol potential were applied, either as a foliar spray or soil drench against the
fungal blast pathogen challenged plants of susceptible cultivar Pusa Basmati 1. The
use of foliar spray enhanced plant growth and related biometrical attributes, while the
soil drench was more effective in reducing disease and improving nutrient
availability. Distinct modulation in the activity of defense, hydrolytic and antioxidant
enzymes, as an indicator of elicitation of host plant metabolism supported the
biocontrol potential of the isolates.
The present study provided novel and interesting information on the hitherto
less-studied phyllospheric microbial communities of rice cultivars from various
agroecologies and the influences of N doses and nutrient availability in soil and leaves
on these communities.The promising, indigenous biocontrol agents were found to be
useful in abating the incidence of the fungal pathogen by altering the microbial
communities favourably in the rice phyllosphere.
 
Date 2018-10-09T04:55:00Z
2018-10-09T04:55:00Z
2017
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/5810075020
 
Language en_US
 
Format application/pdf
 
Publisher DIVISION OF MICROBIOLOGY ICAR–INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI