Microbial diversity in soils suppressive to Fusarium diseases

Abstract

Fusarium species are cosmopolitan soil phytopathogens from the division Ascomycota, which produce mycotoxins and cause significant economic losses of crop plants. However, soils suppressive to Fusarium diseases are known to occur, and recent knowledge on microbial diversity in these soils has shed new lights on phytoprotection effects. In this review, we synthesize current knowledge on soils suppressive to Fusarium diseases and the role of their rhizosphere microbiota in phytoprotection. This is an important issue, as disease does not develop significantly in suppressive soils even though pathogenic Fusarium and susceptible host plant are present, and weather conditions are suitable for disease. Soils suppressive to Fusarium diseases are documented in different regions of the world. They contain biocontrol microorganisms, which act by inducing plants’ resistance to the pathogen, competing with or inhibiting the pathogen, or parasitizing the pathogen. In particular, some of the Bacillus, Pseudomonas, Paenibacillus and Streptomyces species are involved in plant protection from Fusarium diseases. Besides specific bacterial populations involved in disease suppression, next-generation sequencing and ecological networks have largely contributed to the understanding of microbial communities in soils suppressive or not to Fusarium diseases, revealing different microbial community patterns and differences for a notable number of taxa, according to the Fusarium pathosystem, the host plant and the origin of the soil. Agricultural practices can significantly influence soil suppressiveness to Fusarium diseases by influencing soil microbiota ecology. Research on microbial modes of action and diversity in suppressive soils should help guide the development of effective farming practices for Fusarium disease management in sustainable agriculture.

Select Cover Crop Residue and Soil Microbiomes Contribute to Suppression of Fusarium Root and Crown Rot in Barley and Soybean

“…The “no crop” soil treatment was consistently associated with low FRCR in both barley and soybean, even with pathogen inoculum. It is possible that leaving fields undisturbed where no crops were planted enhanced soil stability, promoted weed diversity, and caused subsequent changes in the microbial community that led to disease-suppressive soils [ 5 ].…”

“…The amount of plant material and the particle size of the residue changes the rates of decomposition, thereby creating different microenvironments for the associated microorganisms [ 4 ]. Furthermore, F. graminearum , as well as other Fusarium spp., are known to cause Fusarium head blight (FHB) in crops such as barley and wheat [ 5 , 53 , 54 ]. Increased pathogen load in the residue may increase FHB incidence and severity, as Fusarium resting structures are known to shoot spores high into the air, leading to the infection of aboveground plant parts [ 5 , 54 ].…”

“…Fusarium root and crown rot (FRCR) impact a wide range of economically important crops by causing significant a decrease in crop quality and yield [ 1 , 2 ]. Fusarium resting structures are known to survive harsh winter conditions in soil and crop residues, potentially increasing the susceptibility of subsequently planted crops to FRCR, especially under no-till cropping systems [ 3 , 4 , 5 ]. As such, disease management strategies must involve early preventative measures, such as the use of fungicide seed treatments, to allow crops to establish without being affected by the pathogen early in the growing season [ 6 ].…”

“…As more information is generated on the effects of integrating cover crops into modern rotations, there is a need for more information on the dynamics of pathogen levels in these systems. Understanding the relationship between disease-suppressive soil microbiomes associated with cover crops and FRCR in subsequently planted crops is of great interest [ 5 ]. In this study, representative cover crops from four major crop groups, including brassicas, legumes, forbs, and grasses, were used to better understand the relationship between Fusarium abundance in crop residue and FRCR incidence in subsequently planted barley ( Hordeum vulgare L.) and soybean ( Glycine max (L.) Merr).…”

“…[ 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. FRCR can be difficult to detect as the pathogens may infect the crop, reducing water and nutrient uptake without causing obvious visible symptoms [ 5 ]. As such, it is important that we understand how cover crops used in rotation with barley and soybean affect Fusarium load in the soil and residue and, more importantly, how they affect FRCR incidence and severity.…”