Antifungal activity of volatile compounds produced by Staphylococcus sciuri strain MarR44 and its potential for the biocontrol of Colletotrichum nymphaeae, causal agent strawberry anthracnose

A nonpathogenic endophytic bacterial isolate, recovered from Fragaria × ananassa stolon, and its antifungal activity against Colletotrichum nymphaeae was evaluated under in vitro, in vivo, and greenhouse conditions. Bacterial isolate was identified as Staphylococcus sciuri MarR44 (Strain ID: WDCM 891 = CCSM-B 00640) using phenotypic and biochemical properties and molecular phylogenetic analysis of the 16S rDNA gene sequences. The living cells of strain MarR44 inhibited mycelial growth of C. nymphaeae (52.46%) using dual-culture method. The volatile compounds (VOCs) produced by MarR44 inhibited mycelial growth and conidial germination of C. nymphaeae by 34.52% and 82.81%, respectively. However, inhibition percentage of mycelial growth of pathogen by culture filtrates of the strain MarR44 was lower (23.07%) than that for the two dual culture and volatile compounds assay tests. Moreover, the cell-free-culture filtrates of this strain reduced the biomass and conidial germination of pathogen by 91.89% and 41.10%, respectively. Also, the strain MarR44 was capable of producing protease, chitinase, HCN, siderophore, IAA, gibberellin, and biofilm. The living cells and volatile compounds of the strain MarR44 reduced anthracnose disease at post-harvest on fruit by 52.45% and 72.17%, respectively. Furthermore, disease severity of strawberry anthracnose was reduced using drenching soil and inoculated plants methods by 77.77 and 72.22%, respectively, 60 days after inoculation. The VOCs released by strain MarR44 were analyzed by Gas chromatography-mass spectroscopy (GC-MS). Out of 24 identified VOCs, Mesityl oxide (81.436%), Acetic acid, 2-methylpropyl ester (3.442%), 4-Methyldecane (1.837%), 4-Penten-2-one,4-methyl- (1.739%), Toluene (1.248%), and o-Xylene (1.24%) were the major components. The mode of action of S. sciuri MarR44 on the C. nymphaeae was through the production of antifungal volatile compounds (Antibiosis), which inhibited mycelial growth and conidial germination of pathogen in vitro and fruit decay development in vivo. To the best of our knowledge, this is the first report of S. sciuri having antifungal activity against causal agent strawberry anthracnose. These results indicated that the VOCs of S. sciuri strain MarR44 are promising biofumigant for management of strawberry anthracnose.