The Endophytic Bacteria <i>Bacillus velezensis</i> Lle-9, Isolated from <i>Lilium leucanthum</i>, Harbors Antifungal Activity and Plant Growth-Promoting Effects

Abstract

<i>Bacillus velezensis</i> is an important plant growth-promoting rhizobacterium with immense potential in agriculture development. In the present study, <i>Bacillus velezensis</i> Lle-9 was isolated from the bulbs of <i>Lilium leucanthum</i>. The isolated strain showed antifungal activities against plant pathogens like <i>Botryosphaeria dothidea</i>, <i>Fusarium oxysporum</i>, <i>Botrytis cinerea</i> and <i>Fusarium fujikuroi</i>. The highest percentage of growth inhibition <i>i.e.</i>, 68.56±2.35% was observed against <i>Fusarium oxysporum</i> followed by 63.12 ± 2.83%, 61.67 ± 3.39% and 55.82 ± 2.76% against <i>Botrytis cinerea</i>, <i>Botryosphaeria dothidea</i>, and <i>Fusarium fujikuroi</i>, respectively. The ethyl acetate fraction revealed a number of bioactive compounds and several were identified as antimicrobial agents such as diketopiperazines, cyclo-peptides, linear peptides, latrunculin A, 5α-hydroxy-6-ketocholesterol, (R)-S-lactoylglutathione, triamterene, rubiadin, moxifloxacin, 9-hydroxy-5Z,7E,11Z,14Zeicosatetraenoic acid, D-erythro-C18-Sphingosine, citrinin, and 2- arachidonoyllysophosphatidylcholine. The presence of these antimicrobial compounds in the bacterial culture might have contributed to the antifungal activities of the isolated <i>B. velezensis</i> Lle- 9. The strain showed plant growth-promoting traits such as production of organic acids, ACC deaminase, indole-3-acetic acid (IAA), siderophores, and nitrogen fixation and phosphate solubilization. IAA production was accelerated with application of exogenous tryptophan concentrations in the medium. Further, the lily plants upon inoculation with Lle-9 exhibited improved vegetative growth, more flowering shoots and longer roots than control plants under greenhouse condition. The isolated <i>B. velezensis</i> strain Lle-9 possessed broad-spectrum antifungal activities and multiple plant growth-promoting traits and thus may play an important role in promoting sustainable agriculture. This strain could be developed and applied in field experiments in order to promote plant growth and control disease pathogens.