Abstract：

 Sustainable farming of horticultural plants has been the focus of research during the lastdecade, paying significant attention to alarming weather extremities and climate change, as well asthe pressure of biotic stressors on crops. Microbial biostimulants, including plant growth-promotingbacteria (PGPB) and arbuscular mycorrhizal fungi (AMF), have been proven to increase plant growthvia both direct and indirect processes, as well as to increase the availability and uptake of nutrients,boosting soil quality, increasing plants’ tolerance to abiotic stress and increasing the overall qualityattributes of various horticultural crops (e.g., vegetables, fruit, herbs). The positive effects of microbialbiostimulants have been confirmed so far, mostly through symbiotic interactions in the plant–soil–microbes ecosystem, which are considered a biological tool to increase quality parameters of various horticultural crops as well as to decrease soil degradation. However, more research is neededto address future challenges of crop production through revealing the mechanisms of action andidentifying response patterns of crops to various microbial products. The present review aims topresent the most up-to-date results regarding the practical applications of microbial biostimulants inhorticultural species, including case studies of successful paradigms for the most important microbialgenera of PGPB and AMF. Moreover, the mechanisms of the actions are briefly described whilefuture remarks are also discussed, aiming to suggest further needs to be addressed for the successfulestablishment of microbial biostimulants in sustainable horticultural crop production.

KeyWords:

sustainability; Rhizobium; Mycorrhizas; Azospirillum spp.; Azotobacter spp.; plant

growth-promoting rhizobacteria; arbuscular mycorrhizal fungi