Decoding the Plant Growth Promotion and Antagonistic Potential of Bacterial Endophytes From Ocimum sanctum Linn. Against Root Rot Pathogen Fusarium oxysporum in Pisum sativum

Abstract

The present study demonstrates plant growth promotion and induction of systemic resistance in pea (Pisum sativum) plant against Fusarium oxysporum f.sp. pisi by two bacterial endophytes, Pseudomonas aeruginosa OS_12 and Aneurinibacillus aneurinilyticus OS_25 isolated from leaves of Ocimum sanctum Linn. The endophytes were evaluated for their antagonistic potential against three phytopathogens Rhizoctonia solani, F. oxysporum f. sp. pisi, and Pythium aphanidermatum by dual culture assay. Maximum inhibition of F. oxysporum f. sp. pisi was observed by strains OS_12 and OS_25 among all root rot pathogens. Scanning electron microscopy of dual culture indicated hyphal distortion and destruction in the case of F. oxysporum f. sp. pisi. Further, volatile organic compounds (VOCs) were identified by gas chromatography–mass spectrometry (GC-MS). The GC-MS detected eight bioactive compounds from hexane extracts for instance, Dodecanoic acid, Tetra decanoic acid, L-ascorbic acid, Trans-13-Octadecanoic acid, Octadecanoic acid. Both the endophytes exhibited multifarious plant growth promoting traits such as indole acetic production (30–33 μg IAA ml–1), phosphate solubilization, and siderophore and ammonia production. Pot trials were conducted to assess the efficacy of endophytes in field conditions. A significant reduction in disease mortality rate and enhancement of growth parameters was observed in pea plants treated with consortium of endophytes OS_12 and OS_25 challenged with F. oxysporum f.sp. pisi infection. The endophytic strains elicited induced systemic resistance (ISR) in pathogen challenged pea plants by enhancing activities of Phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO), ascorbate oxidase (AO), catalase (CAT) and total phenolic content. The endophytes reduced the oxidative stress as revealed by decrease in malondialdehyde (MDA) content and subsequently, lipid peroxidation in host plant leaves. Robust root colonization of pea seedlings by endophytes was observed by scanning electron microscopy (SEM) and fluorescence microscopy. Thus, plant growth promoting endophytic P. aeruginosa and A. aneurinilyticus can be further exploited through bio-formulations for sustainable protection of crops against root rot diseases as bio-control agents.

Harnessing the Antifungal Potential of Seed Bacteriome against Major Seed and Soil-borne Pathogens in Blackgram

“…Endophytic bacteria showing beneficial influence on the growth, development, and protection of plants against diseases facilitates sustainable approaches in agriculture [18][19][20]. Twenty five bacterial strains were screened in various dual culture assays, from which P. aeruginosa PPB3 and A. aneurinilyticus PPB9 were selected for superior antagonistic activity against F. oxysporum [21]. The formation of inhibition zone between the endophyte and the pathogen on agar medium is usually considered as a result of production of antibiotics, pH change and competition for nutrients [22].…”

Secondary Metabolites Produced by Plant Growth-Promoting Bacterial Endophytes

“…tritici (wheat take-all fungus). (iii) Gupta et al [ 42 ] found a large decrease in the disease mortality of pea plants infected with the fungal phytopathogen Fusarium oxysporum when they were treated with a consortium of endophytic PGPB that produced VOCs and elicited ISR. (iv) Hamaoka et al [ 43 ] noted that the endophytic PGPB Bacillus velezensis KOF112, originally isolated from Japanese wine grapes, inhibited the mycelial growth of the fungal phytopathogens Botrytis cinerea , Colletotrichum gloeosporioides , and Phytophthora infestans (where strain KOF112 synthesized antibiotics and elicited ISR in treated plants).…”

Aneurinibacillus uraniidurans sp. nov., a uranium-resistant bacterium isolated from uranium-contaminated soil

“…The genus Aneurinibacillus is a new genus based on the reclassification of the Bacillus brevis and Bacillus aneurinolyticus groups and belongs to the family Paenibacillaceae [1,2]. Members of the genus Aneurinibacillus have a broad range of promising and useful biological functions, such as plant diseases biocontrol [3,4], the biosynthesis of polyhydroxyalkanoates (PHA) [5], lignocellulose biomass degradation [6] and plant-growth promotion [7][8][9]. Aneurinibacillus species have also shown promising potential in terms of resisting multiple heavy metals [10,11].…”