Stenotrophomonas rhizophila Ep2.2 inhibits growth of Botrytis cinerea through the emission of volatile organic compounds, restricts leaf infection and primes defense genes

The bacterium Stenotrophomonas rhizophila is known to be beneficial for plantsand has been frequently isolated from the rhizosphere of crops. In the presentwork, we isolated from the phyllosphere of an ornamental plant an epiphyticstrain of S. rhizophila that we named Ep2.2 and investigated its possibleapplication in crop protection. Compared to S. maltophilia LMG 958, a well-known plant beneficial species which behaves as opportunistic human pathogen,S. rhizophila Ep2.2 showed distinctive features, such as different motility, agenerally reduced capacity to use carbon sources, a greater sensitivity tofusidic acid and potassium tellurite, and the inability to grow at the humanbody temperature. S. rhizophila Ep2.2 was able to inhibit in vitro growth of theplant pathogenic fungi Alternaria alternata and Botrytis cinerea through theemission of volatile compounds. Simultaneous PTR-MS and GC-MS analysesrevealed the emission, by S. rhizophila Ep2.2, of volatile organic compounds(VOCs) with well-documented antifungal activity, such as furans, sulphur-containing compounds and terpenes. When sprayed on tomato leaves andplants, S. rhizophila Ep2.2 was able to restrict B. cinerea infection and to primethe expression of Pti5, GluA and PR1 plant defense genes