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Aims: To isolate and characterize indigenous bacterial endophytes from cultivars of switchgrass and study their antimicrobial and growth promoting potential. Methods and Results: The diversity, molecular and biochemical characterizations of indigenous and culturable bacterial endophytes residing in leaves of switchgrass have not been studied previously. This study describes the characterization of 31 bacterial endophytes from three switchgrass cutlivars: Cave-in Rock, Blue Jacket and Tecumseh. Molecular and phylogenetic analysis based on the 16S rRNA sequence grouped the endophytes into eight different taxa that shared high homology of 98-99% with other known sequences. Bacterial endophytes were identified as Microbacterium testaceum, Curtobacterium flaccumfaciens, Bacillus subtilis and Bacillus pumilus, Pseudomonas fluorescens, Sphingomonas parapaucimobilis, Serratia sp. and Pantoea ananatis. Some endophytes were detected in switchgrass seeds and in plants that originated from seeds collected a year earlier, confirming vertical transmission to the next generation of the host. Selected endophytes produced cellulases and were capable of solubilizing inorganic phosphorus. Analysis of cell-free culture filtrate of selected strains using direct infusion orbitrap mass spectrometry confirmed the presence of several well-characterized lipopeptide toxins and phytohormones. Re-inoculation of the roots of switchgrass seedlings with endophytes singly or combined confirmed their migration to the upper aerial parts of the plant. Conclusions: Our findings suggest that switchgrass leaves harbour a diversity of bacterial endophytes, some of which could potentially be applied as growth promoting bacteria. Significance and Impact of the Study: This is the first report on the characterization of indigenous bacterial endophytes and their potential use as biofertilizers.

Cool spring and early summer temperatures have limited the adoption of warm season grasses in northern environments like eastern Canada. This study characterized the performance of nine switchgrass (Panicum virgatum L.) populations (‘Blackwell’, ‘Cave‐in‐Rock’, ‘Dakota’, ‘Forestburg’, ‘New Jersey SO’, ‘Pathfinder’, ‘Sunburst’, ‘Shelter’, and ‘ND3743’) in southwestern Quebec. These populations were evaluated for 3 yr on a St. Bernard sandy clay loam (Typic Hapludalf) near Montreal. Leaf area development patterns during the season fitted second degree polynomial models, increasing with time after planting and decreasing in the fall. Maximum leaf area index (LAI) ranged from 6.1 to 8 m2 m−2 with Cave‐in‐Rock and New Jersey 50 having the highest LAIs. The populations had different vertical leaf area distributions. For Blackwell, Cave‐in‐Rock, and Shelter, more than 50% of the leaf area was in the top third of the canopy. New Jersey 50 and Pathfinder had uniform vertical leaf area distributions through the canopy. Light extinction coefficients (k) ranged from 0.57 to 0.72. Average end‐of‐season biomass yields were 8477, 9943 and 10 869 kg ha−1 in 1993, 1994, and 1995, respectively. The relationship between end of season yield and leaf area duration was linear. Cave‐in‐Rock, New Jersey 50, and Blackwell produced the greatest yields. All entries had high neutral detergent fiber (NDF) [810‐870 g kg−1 dry matter (DM)] and acid detergent fiber (ADF) (510‐570 g kg−1 DM). Nitrogen and ash concentrations ranged from 3.2 to 8.2 and 47 to 66 g kg−1 DM, respectively. This study showed that switchgrass can be successfully grown in southwestern Quebec.

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