Use of PGPR for Controlling Soilborne Fungal Pathogens: Assessing the Factors Influencing Its Efficacy

Abstract

Management of soilborne fungal plant pathogens in sustainable cropping systems should be based on strategies that integrate all available control measures. The use of PGPR is recognized as one of the most promising methods for controlling soilborne fungal plant pathogens. However, we are currently far away of being able to understand and exploit the full potential of PGPR as an effective disease management strategy at field scale. Both, abiotic and biotic factors modulate metabolic processes of plants and microorganisms within their respective biological limits, and consequently may modify interactions among them in a given pathosystem. It is well documented that incidence and severity of plant diseases are modulated by the soil environment and that the efficacy of some PGPR biocontrol agents decrease as conditions become more favorable for disease development. Soil biotic and abiotic factors may influence biological control mediated by PGPR by either (1) predisposing pathogens to microbial antagonism, (2) regulating the growth or production of metabolites by specific antagonists, or (3) modulating disease development and consequently the level of disease suppression achieved. To complicate more the scenario, there is global observational evidence that many natural biological systems are being affected by regional climate changes. Many environmental factors associated to climate change, particularly temperature increase, may influence the mechanisms of biocontrol mediated by PGPR, but there is little knowledge of how those specific factors may affects the interactions among soilborne fungal pathogens and PGPR. Research on the effects of climate change on plant diseases is limited, especially on biocontrol. Currently, the use of climate risk mapping tools may facilitate the geographic assessment of potential pathogen and PGPR distribution and how those factors may interact under the different scenarios of climatic change and may help in designing new strategies for the efficient use and improved performance of well-performing PGPR as effective biocontrol agents of soilborne fungal plant pathogens.