Elucidating the differential antiviral action of a plant growth promoting rhizobacterium against three genetically distant virus species

Viruses pose a major threat to global agriculture, leading to substantial economic losses, whereas effective control measures remain limited. Plant Growth-Promoting Microorganisms (PGPMs) are used as an environmentally friendly approach against bacterial and fungal diseases. Although accumulating evidence show their antiviral potential their use remains limited mainly due to their variable efficacy against distinct viruses. In a previous study, we reported the differential antiviral effect of <i>Bacillus amyloliquefaciens</i> strain MBI600 (Serifel^®, BASF) in tomato plants against tomato spotted wilt virus (TSWV, <i>Orthotospovirus tomatomaculae</i>) and potato virus Y (PVY, <i>Potyvirus yituberosi</i>). In this study, we aimed to elucidate the molecular basis of the differential response recorded in the antiviral efficacy of MBI600 against genetically distinct virus species. To this end, the antiviral potential of MBI600 was examined against two more important viruses of tomato cultivation, tomato yellow leaf curl virus (TYLCV, <i>Begomovirus coheni</i>), and cucumber mosaic virus (CMV, <i>Cucumovirus CMV</i>). MBI600 exhibited strong antiviral activity against TYLCV but not against CMV. The transcriptomic analysis of plants treated with MBI600 in the absence and presence of TSWV, TYLCV and CMV, revealed systemic host responses associated with the effectiveness level of the PGPM's antiviral ability. Our results provide a better understanding of the selective nature of PGPM-mediated antiviral resistance and support PGPMs usage as an effective strategy against viral diseases.