Frontiers in Microbiology (Dec 2022)

Rice leaf endophytic Microbacterium testaceum: Antifungal actinobacterium confers immunocompetence against rice blast disease

  • Asharani Patel,
  • Kuleshwar Prasad Sahu,
  • Sahil Mehta,
  • Alexander Balamurugan,
  • Mukesh Kumar,
  • Neelam Sheoran,
  • Shanu Kumar,
  • Charishma Krishnappa,
  • Mushineni Ashajyothi,
  • Aditi Kundu,
  • Tushar Goyal,
  • Prabhakaran Narayanasamy,
  • Aundy Kumar

DOI
https://doi.org/10.3389/fmicb.2022.1035602
Journal volume & issue
Vol. 13

Abstract

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Genetic and functional characteristics of rice leaf endophytic actinobacterial member, Microbacterium are described. Morphotyping, multilocus sequence analysis and transmission electron microscopy indicated the species identity of the endophytic bacterium, OsEnb-ALM-D18, as Microbacterium testaceum. The endophytic Microbacterium showed probiotic solubilization of plant nutrients/minerals, produced hydrolytic enzyme/phytohormones, and showed endophytism in rice seedlings. Further, the endophytic colonization by M. testaceum OsEnb-ALM-D18 was confirmed using reporter gene coding for green fluorescence protein. Microbacterium OsEnb-ALM-D18 showed volatilome-mediated antibiosis (95.5% mycelial inhibition) on Magnaporthe oryzae. Chemical profiling of M. testaceum OsEnb-ALM-D18 volatilome revealed the abundance of 9-Octadecenoic acid, Hexadecanoic acid, 4-Methyl-2-pentanol, and 2,5-Dihydro-thiophene. Upon endobacterization of rice seedlings, M. testaceum altered shoot and root phenotype suggestive of activated defense. Over 80.0% blast disease severity reduction was observed on the susceptible rice cultivar Pusa Basmati-1 upon foliar spray with M. testaceum. qPCR-based gene expression analysis showed induction of OsCERK1, OsPAD4, OsNPR1.3, and OsFMO1 suggestive of endophytic immunocompetence against blast disease. Moreover, M. testaceum OsEnb-ALM-D18 conferred immunocompetence, and antifungal antibiosis can be the future integrated blast management strategy.

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