Salicylic Acid [KLH]

After three decades of the amazing progress made on molecular studies of plant-microbe interactions (MPMI), we have begun to ask ourselves "what are the major questions still remaining?'' as if the puzzle has only a few pieces missing. Such an exercise has ultimately led to the realization that we still have many more questions than answers. Therefore, it would be an impossible task for us to project a coherent ``big picture'' of theMPMI field in a single review. Instead, we provide our opinions on where we would like to go in our research as an invitation to the community to join us in this exploration of new MPMI frontiers.

In nature, plants are constantly exposed to a varied abiotic and biotic stresses or their combinations, limiting the productivity of major crops, including wheat. Combinations of drought and soil-borneFusarium-instigated diseases are the most common combinations of stresses, significantly reducing wheat yield around the world. Here, were analyzed the potential of application of endophytic bacteriaBacillus subtilis(strain 10-4) together with the natural signal molecule salicylic acid (SA) to improve growth and tolerance ofTriticum aestivumL. (wheat) plants under combined drought andFusarium culmorum-instigated root rot (FRR) stresses. It was revealed that pre-sowing treatment withB. subtilis10-4, SA, andB. subtilis10-4 + SA, both under normal and combined drought conditions, notably reduced (by 50-80% or more) the incidence of FRR development in wheat plants, with the most notable effect forB. subtilis10-4 + SA (wherein disease symptoms were almost absent). Moreover,B. subtilis10-4, SA, and especiallyB. subtilis10-4 + SA increased plant growth (root and shoot length, fresh and dry biomass) under normal (up to 20-50%), drought (up to 15-40%), FRR (up to 15-30%), and combined drought + FRR stresses (up to 20%), with the maximum effect forB. subtilis10-4 + SA. Additionally,B. subtilis10-4, SA, andB. subtilis10-4 + SA decreased stress (drought, FRR, and combined drought + FRR)-instigated lipid peroxidation and osmotic damages of plant cells. The findings indicate that endophytic bacteriaB. subtilis10-4 alone and in a mixture with SA may be used as an effective eco-friendly agent to improve wheat growth and tolerance under the influence of drought, FRR, and combinations of these stresses.