ISOLATION AND EVALUATION OF Bacillus AND Pseudomonas SPECIES FOR PLANT GROWTH PROMOTING AND PATHOGEN SUPPRESSING TRAITS IN SUGARCANE
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Date
2023-12-18
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Acharya N G Ranga Agricultural University
Abstract
The present study on “Isolation and evaluation of Bacillus and Pseudomonas species for plant growth promoting and pathogen suppressing traits in sugarcane” was conducted at RARS, Anakapalle during 2021-22, where 40 isolates of Bacillus and Pseudomonas species were isolated on specific media with selective supplements from rhizoplane of different sugarcane genotypes. Twenty each of Gram-positive and Gram-negative isolates were further identified as Bacillus and Pseudomonas species respectively by PCR amplification with Bacillus (BCF1 and BCR2) and Pseudomonas (Psmn289 and Psmn1258) specific primers.
Morphologically most of the colonies formed by Bacillus isolates were round in shape with even margins, flat, opaque and smooth textured with creamy to milky white pigmentation with few exceptions. In case of Pseudomonas many of the isolates have round or irregular, flat, opaque, smooth textured and creamy to milky whitish colonies with undulated margin with few exceptions.
All the 40 isolates were tested for their antagonistic activity against Colletotrichum falcatum and Fusarium sacchari through dual culture assay. Among them six isolates viz., SRB2 (65.74%), SRB4 (54.81%), SRB20 (80.37%), SRP3 (44.26%), SRP19 (80.78%) and SRP20 (69.81%) had significantly inhibited the growth of C. falcatum and five isolates viz., SRB2, SRB20, SRP3, SRP19 and SRP20 have shown inhibition of 52.30, 35.00, 30.93, 46.30 and 39.30% against Fusarium sacchari respectively. The observations at interaction zone revealed variation in growth pattern of the test fungus with hyphal thinning, wrinkling, hyphal tip shearing, protoplasm disintegration, clustering of hyphae and formation of intercellular and terminal chlamydospores. The volatile and non-volatile compounds from the potential isolates substantially reduced the radial growth of C. falcatum and F. sacchari.
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The highly potential antagonistic isolates (SRB2, SRB20, SRP19 and SRP20) were identified as Bacillus inaquosorum, Bacillus vallismortis, Pseudomonas chlororaphis subsp. aurantiaca and Pseudomonas aeruginosa respectively by partial sequencing of 16S-23S intergenic region amplified by 16F945 and 23R458 primers.
All the isolates were qualitatively tested for plant growth promoting and pathogen suppressing traits like, P solubilization (60% of the total isolates), IAA production (30%), protease activity (57.5%), cellulase activity (17.5%), chitinase activity (12.5%), HCN production (10%), siderophore production (27.5%), pyocyanin and fluorescein production (15 and 20% of Pseudomonas isolates respectively) and Antimicrobial peptide (AMP) genes like, fenD (60%), bmyB (50%), spaS (30%) and ituC (30%) for Bacillus isolates and phlD (20%), prnD (20%), phz (15%) and pltC (10%) for Pseudomonas isolates.
Sett bacterization had positive impact on sett germination with negligible to very low increase in shoot length and low to higher increase in seedling vigour ranging from 23.85 (SRB1) to 92.91% (SRB11) and 8.80 (SRP14) to 98.73% (SRP17) of increase over control in Bacillus and Pseudomonas treated trays respectively.
Sett treatment with potential antagonistic isolates revealed that four (SRB2, SRB20, SRP19 and SRP20) out of six isolates were found effective in controlling pre-emergence and post emergence seedling mortality in C. falcatum and F. sacchari inoculated pots under greenhouse conditions. The isolates SRP19 (Pseudomonas chlororaphis subsp. aurantiaca) and SRB20 (Bacillus vallismortis) were considered to be the most promising isolates in improving plant health as evident by their performance in PGP and disease suppressing activity.