Identification of actinobacteria from rhizosphere soils for growth promotion in tomato
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Date
2021-01-26
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College of Horticulture and Forestry, Dr YSP UHF, Neri, Hamirpur (H.P.)
Abstract
The present investigation entitled “Identification of actinobacteria from rhizosphere soils for
growth promotion in tomato” was carried out during 2019-2020 with the aim to explore native
actinomycetes from rhizosphere of tomato crop grown at different locations in district Kullu and
Hamirpur of Himachal Pradesh. A total of 109 actinobacterial isolates were obtained using different
selective media for isolation viz., actinomycete isolation agar medium, yeast malt agar medium and
starch M protein agar medium and the preliminary screening of the isolates for plant growth promoting
attributes (PGP) attributes was carried out. It was found that only 88.99% of the total isolates showed
phosphate (P) solubilization on Pikovskaya’s agar medium and the phosphate solubilization index
varied widely from 1.11 to 6.0. All actinobacterial isolates displayed growth on nitrogen free Jensen’s
medium and only 5.50% isolates exhibited siderophore production. The inhibition of fungal pathogens
viz. Alternaria sp, Fusarium sp, Phytophthora sp and Sclerotinia sp., was demonstrated by 28.44%,
11.92%, 15.59% and 12.84% actinobacterial isolates, respectively and four isolates (NDF-10, HMS-4,
HMM-1 and HMM-4) showed inhibition against all the phytopathogenic fungi.On the basis of initial
screening, only fifteen actinobacterial isolates were further evaluated and found to exhibit high P
solubilization (718.16 to 1418.16 μg/ml) in National Botanical Research Institute’s Phosphate broth
with tricalcium phosphate and high indole-3-acetic acid/IAA (11.56 to 21.35 μg/ml) production.
Maximum P solubilization and IAA production was observed in isolate KLK-8. The production of
extracellular enzymes amylase, cellulase, gelatinase, lipase and protease varied among the isolates. All
the fifteen actinobacterial isolates with filamentous morphology varied in their biochemical
characteristics. Screening of actinomycete isolates for in vitro tomato seed germination and growth
studies in filter paper assay revealed best performance of seeds treated with isolate KLK-8 which
showed a significant increase in per cent germination, root length, shoot length and vigour index over
untreated control. On the basis of 16S rRNA gene sequence analysis, three promising actinobacterial
isolates KLK-8, HMM-1 and HMS-8 were identified as Streptomyces tendae strain KLK8,
Streptomyces sp. strain HMM1 and Streptomyces sp. strain HMS8, respectively. The present study
clearly indicates that native actinomycetes exhibit promising PGP attributes and could serve as
bioinoculants to achieve more sustainable and environment friendly crop production.