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

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

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1035602

DOI=10.3389/fmicb.2022.1035602

ISSN=1664-302X

ABSTRACT=<p>Genetic and functional characteristics of rice leaf endophytic actinobacterial member, <italic>Microbacterium</italic> are described. Morphotyping, multilocus sequence analysis and transmission electron microscopy indicated the species identity of the endophytic bacterium, OsEnb-ALM-D18, as <italic>Microbacterium testaceum</italic>. The endophytic <italic>Microbacterium</italic> showed probiotic solubilization of plant nutrients/minerals, produced hydrolytic enzyme/phytohormones, and showed endophytism in rice seedlings. Further, the endophytic colonization by <italic>M. testaceum</italic> OsEnb-ALM-D18 was confirmed using reporter gene coding for green fluorescence protein. <italic>Microbacterium</italic> OsEnb-ALM-D18 showed volatilome-mediated antibiosis (95.5% mycelial inhibition) on <italic>Magnaporthe oryzae</italic>. Chemical profiling of <italic>M. testaceum</italic> 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, <italic>M. testaceum</italic> 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 <italic>M. testaceum</italic>. qPCR-based gene expression analysis showed induction of <italic>Os</italic>CERK1, <italic>Os</italic>PAD4, <italic>Os</italic>NPR1.3, and <italic>Os</italic>FMO1 suggestive of endophytic immunocompetence against blast disease. Moreover, <italic>M. testaceum</italic> OsEnb-ALM-D18 conferred immunocompetence, and antifungal antibiosis can be the future integrated blast management strategy.</p>