Fusarium Community Research Articles

Management factors affecting size and structure of soil Fusarium communities under irrigated maize in Australia

Fungi in the genus Fusarium are ubiquitous in agricultural soils and have a wide range of ecological roles. We conducted a series of field trials, glasshouse trials, and soil microcosm experiments to assess the effects of stubble and N management, crop type, incorporation of residue originating from different plants and seed-applied fungicides on soil Fusarium. A community level approach was used based on PCR-DGGE and a semi-quantitative nested qPCR approach. Soil Fusarium communities were found to be primarily affected by plant residue inputs. In a field trial, incorporation of maize residue into soil significantly increased the relative abundance of Fusarium Ef1α gene copies ( P < 0.001) and increased the diversity of Fusarium genotypes present in the field when compared to stubble burned treatments. In particular, the important mycotoxin-producing Fusarium verticillioides was present where stubble had been retained and absent where stubble was burnt. Fusarium oxysporum was common in soil regardless of stubble management. In the field trial, the application of mineral N fertiliser (329 kg N ha −1 year −1) had no effect on abundance or diversity of soil Fusarium ( P > 0.05). Glasshouse trials tested the effects of fungicides and crop rotation on the diversity and abundance of soil Fusarium spp. Using soil repeatedly cropped with maize (5 years), the subsequent growth of neither canola, wheat nor maize significantly altered the relative abundance of Fusarium in soil ( P < 0.05), but growth of adzuki bean resulted in a significant decrease ( P < 0.05). Furthermore, the growth of different plants had no effect on the species of Fusarium present in the soil. However, in a microcosm experiment, the return of residues of these plants to soil (at equivalent dry weights) resulted in increases to the size and change to the composition of the Fusarium community ( P = 0.001). Treatment of maize seed with the fungicides metalaxyl-M, tolclofos-methyl, or fludioxonil increased plant growth and the relative abundance of Fusarium Ef1α genes in DNA extracted from the bulk soil. This may have occurred by suppressing soil microorganisms competing with Fusarium for plant residues. Fungicide addition also effected a short-term change to the Fusarium community structure. This work clearly demonstrates the effects of crop residue quantity and quality (origin) on soil Fusarium communities, indicating its importance for integrated management of Fusarium in production systems.

Relationships between Fusarium population structure, soil nutrient status and disease incidence in field-grown asparagus

Fusarium species cause important diseases in many crops. Lack of knowledge on how Fusarium species and strains interact with their environment hampers growth management strategies to control root diseases. A field experiment involving asparagus as host plant and three phosphorus fertilization levels was designed to examine the seasonal changes and ecological relationships between Fusarium populations and their soil and plant environments. Fusarium taxa were identified and assessed using PCR-denaturing gradient electrophoresis of the EF1-alpha gene. Resulting profiles were analyzed with respect to 17 ecological parameters measured during the three main asparagus phenological phases across a growing season. Multivariate statistical analysis showed that Fusarium population structure was strongly influenced by soil P level while seasonal variation was less important. A significant relationship between Fusarium population composition and Fusarium crown and root rot incidence was also found in September. Canonical analysis further revealed significant relationships between Fusarium population structure, and plant manganese and iron contents, soil dehydrogenase activity and soil calcium concentration. If higher Fusarium crown and root rot incidence is related to the Fusarium community structure, strategies to reduce the incidence in asparagus plantations may be found through manipulation of the soil fertility.

Changes in Communities of Fusarium and Arbuscular Mycorrhizal Fungi as Related to Different Asparagus Cultural Factors

Asparagus (Asparagus officinalis) is a high-value perennial vegetable crop that has shown a marked decline in productivity after many years of continuous harvesting. This decline is caused by an increase in both abiotic (autotoxicity, harvesting pressure) and biotic stresses [fungal infections, mainly Fusarium crown and root rot (FCRR)]. To gain insight into disease development and possible mitigation strategies, we studied the effects of harvesting, time in the growing season, and field age on FCRR development, Fusarium species composition, and arbuscular mycorrhizal fungi (AMF) communities in both a controlled field experiment and an ecological survey of commercial fields. In one experiment, a 3-year-old asparagus field was subdivided into plots that were harvested or not and sampled throughout the growing season to assess short-term dominant Fusarium species shifts. In addition, diseased and healthy asparagus plants sampled from six commercial fields in the same geographical region were used to assess Fusarium and AMF communities in relation to different parameters. Fusarium and AMF communities were described by using a polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) approach, and results were analyzed by mainly correspondence analysis and canonical correspondence analysis. Results showed that dominant Fusarium taxa assemblages changed throughout the growing season. Harvested plots had significantly more FCRR symptomatic plants at the end of the growing season, but this effect was not related with any trend in Fusarium community structure. Sampling site and plant age significantly influenced AMF community structure, whereas only sampling site consistently influenced the Fusarium community. Diseased and healthy plants harbored similar Fusarium and AMF communities. Shifts in Fusarium community might not be responsible for different disease incidence because they are ubiquitous regardless of plant health status or harvesting regime. The different incidence noted might rather be related to plant physiology, antagonist microbial communities, or soil parameters.

Gibberella konza (Fusarium konzum) sp. nov. from prairie grasses, a new species in the Gibberella fujikuroi species complex

The Gibberella fujikuroi species complex (Fusarium section Liseola and allied taxa) is composed of an increasingly large number of morphological, biological and phylogenetic species. Most of the known species in this group have been isolated from agricultural ecosystems or have been described from a small number of isolates. We sampled Fusarium communities from native prairie grasses in Kansas and recovered a large number of isolates that superficially resemble F. anthophilum. We used a combination of morphological, biological and molecular characters to describe a new species, Gibberella konza (Gibberella fujikuroi mating population I [MP-I]), from native prairie grasses in Kansas. Although female fertility for field isolates of this species appears to be low, G. konza is heterothallic, and we developed reliably female fertile mating population tester strains for this species. The F. konzum anamorph is differentiated from F. anthophilum and from other Fusarium species in section Liseola by mating compatibility, morphology, AFLP fingerprint profile and differences in β-tubulin DNA sequence.

Gibberella konza (Fusarium konzum) sp. nov. from Prairie Grasses, a New Species in the Gibberella fujikuroi Species Complex

The Gibberella fujikuroi species complex (Fusarium section Liseola and allied taxa) is composed of an increasingly large number of morphological, biological and phylogenetic species. Most of the known species in this group have been isolated from agricultural ecosystems or have been described from a small number of isolates. We sampled Fusarium communities from native prairie grasses in Kansas and recovered a large number of isolates that superficially resemble F. anthophilum. We used a combination of morphological, biological and molecular characters to describe a new species, Gibberella konza (Gibberella fujikuroi mating population I [MP-I]), from native prairie grasses in Kansas. Although female fertility for field isolates of this species appears to be low, G. konza is heterothallic, and we developed reliably female fertile mating population tester strains for this species. The F. konzum anamorph is differentiated from F. anthophilum and from other Fusarium species in section Liseola by mating compatibility, morphology, AFLP fingerprint profile and differences in β-tubulin DNA sequence.