Isolation and Identification of Shoot-Tip Associated Endophytic Bacteria from Banana cv. Grand Naine and Testing for Antagonistic Activity against <i>Fusarium oxysporum</i> f. sp. <i>cubense</i>

Abstract

Endophytic bacteria colonizing the shoot-tips of banana cv. Grand Naine were isolated and tested for the antagonistic activity against the Panama wilt pathogen Fusarium oxysporum f. sp. cubense (Foc). Pre-isolation, the suckers were given extensive disinfection treatments and the homogenate from the excised shoot-tip portion was plated on nutrient agar (NA) and trypticase soy agar (TSA). This yielded altogether 47 isolates: 26 on NA and 21 on TSA, respectively, from the 10 suckers collected during August to February. The number of bacterial isolates obtained per sucker varied from one to 15 based on colony characteristics registering up to 10 distinct species per shoot-tip based on 16S rRNA sequence analysis. The 47 isolates belonged to 19 genera and 25 species under the phylogenetic classes of Actinobacteria, α-and γ-Proteobacteria and Firmicutes. Actinobacteria constituted the predominant phylum (55% isolates) with the constituent genera of Arthrobacter, Brevibacterium, Corynebacterium, Curtobacterium, Kocuria, Kytococcus, Micrococcus, Naumanella, Rothia and Tessaracoccus spp. and an unidentified isolate belonging to the family Frankiaceae. Proteobacteria constituted the second major phylum (Brevundimonas, Enterobacter, Klebsiella, Pseudomonas, Serratia and Sphingomonas spp.) followed by Firmicutes (Bacillus and Staphylococcus spp.). Antagonistic activity of the endophytes against Foc was tested through agar plate assays (pit and spot applications on fungal lawn) employing potato dextrose agar and NA. Endophytic Pseudomonas aeruginosa (isolate GNS.13.2a) which was associated with a single sucker showed significant growth inhibition effect on Foc while Klebsiella variicola (GNS.13.3a) and Enterobacter * Corresponding author.A. C. Sekhar, P. Thomas 944 cloacae (GNS13.4a) exhibited moderate inhibition. The study brings out considerable sucker to sucker variation in the associated cultivable endophytic bacteria in "Grand Naine" banana and identifies a few bacterial endophytes with biocontrol potential against the devastating Foc pathogen.

Establishment of an in vitro culture of Pelargonium × domesticum cultivars characterized by different growth requirements

“…pelargonii could be indexed in explants taken E. from cultivars of Pelargonium × domesticum. Sekhar and Thomas (2015) isolated Fusarium oxysporum f. sp. cubense from shoot-tips of a banana cultivar.…”

Isolation and identification of bacterial endophytes from Crinum macowanii Baker

“…Bacillus and Acitenobacter spp. are part of the 16 genera that have been identified as endophytes (Sekhar and Thomas, 2015;Gouda et al, 2016). These species have been isolated from roots, stem and leaves of L. japonica (Zhao et al, 2015) and sterilized roots of Beta vulgaris (Shi et al, 2011).…”

Effects Due to Rhizospheric Soil Application of an Antagonistic Bacterial Endophyte on Native Bacterial Community and Its Survival in Soil: A Case Study with Pseudomonas aeruginosa from Banana

“…cv. Grand Naine ( Sekhar and Thomas, 2015 ). The prime target was to explore by testing these isolates for potential biocontrol of banana wilt disease caused by the soil-borne vascular pathogen Fusarium oxysporum f. sp.…”

“…cubense ( Foc ), a serious limiting factor in major banana growing areas world over ( Stover, 1962 ; Ploetz et al, 2003 ). Evaluating the 47 endophytic banana strains against Foc , one isolate (GNS.13.2a) exhibited significant antagonistic activity against the pathogen in direct in vitro challenge assays and this isolate was identified as Pseudomonas aeruginosa ( Sekhar and Thomas, 2015 ). This isolate also displayed antagonistic effects against the soil-borne pathogens, Ralstonia solanacearum from tomato and Erwinia carotovora from banana and thus a potential biocontrol agent against multiple diseases.…”

“…Further, some strains of P. aeruginosa have been reported as plant growth promoters ( Pandey et al, 2012 ; Gupta et al, 2013 ; Gupta G. et al, 2015 ) or useful in weed management ( Lakshmi et al, 2015 ). Thus the endophytic strain of P. aeruginosa from banana ( Sekhar and Thomas, 2015 ) appeared to form a good model system for studying the twin aspects of (i), the ability of an endophytic strain to survive in soil and (ii), effects due to the introduced microorganism with pathogen-antagonistic potential on native soil microbial community. Further, Pseudomonas sp.…”