Agricultural factors affecting Fusarium communities in wheat kernels

Abstract

Fusarium head blight (FHB) is a devastating disease of cereals caused by Fusarium fungi. The disease is of great economic importance especially owing to reduced grain quality due to contamination by a range of mycotoxins produced by Fusarium. Disease control and prediction is difficult because of the many Fusarium species associated with FHB. Different species may respond differently to control methods and can have both competitive and synergistic interactions. Therefore, it is important to understand how agricultural practices affect Fusarium at the community level.Lower levels of Fusarium mycotoxin contamination of organically produced cereals compared with conventionally produced have been reported, but the causes of these differences are not well understood. The aim of our study was to investigate the effect of agricultural factors on Fusarium abundance and community composition in different cropping systems. Winter wheat kernels were collected from 18 organically and conventionally cultivated fields in Sweden, paired based on their geographical distance and the wheat cultivar grown. We characterised the Fusarium community in harvested wheat kernels using 454 sequencing of translation elongation factor 1-a amplicons. In addition, we quantified Fusarium spp. using real-time PCR to reveal differences in biomass between fields.We identified 12 Fusarium operational taxonomic units (OTUs) with a median of 4.5 OTUs per field. Fusarium graminearum was the most abundant species, while F. avenaceum had the highest occurrence. The abundance of Fusarium spp. ranged two orders of magnitude between fields. Two pairs of Fusarium species co-occurred between fields: F. poae with F. tricinctum and F. culmorum with F. sporotrichoides. We could not detect any difference in Fusarium communities between the organic and conventional systems. However, agricultural intensity, measured as the number of pesticide applications and the amount of nitrogen fertiliser applied, had an impact on Fusarium communities, specifically increasing the abundance of F. tricinctum. There were geographical differences in the Fusarium community composition where F. graminearum was more abundant in the western part of Sweden. The application of amplicon sequencing provided a comprehensive view of the Fusarium community in cereals. This gives us better opportunities to understand the ecology of Fusarium spp., which is important in order to limit FHB and mycotoxin contamination in cereals.

What influences the composition of fungi in wheat grains?

“…The impact of temperature was not evaluated because the average temperatures in the crucial period of ear infection were similar throughout all investigation years and did not exceed 17-19°C. The present investigation showed that F. avenaceum was the dominant species, which agrees with several other findings [25][26][27]. Similarly, a high occurrence of F. poae was detected in our research, which also supports the data in the literature [22,28].…”

“…In Sweden, ploughing has been recognized as an important tool to control Fusarium head blight [26]. On the other hand, Blandino et al [9] determined that the successful control of Fusarium head blight could be achieved only by combining different factors; a single factor, such as the management of plant residues, was not effective.…”

A fungal mock community control for amplicon sequencing experiments

“…This was made plain in my mock communities through the formation of an "unclassified Fusarium" phylotype, and the reassignment of reads to and from this phylotype during data processing. It is well known that the ITS locus is not well suited to differentiating among Fusarium species and that alternative markers perform better for this genus (Karlsson, Friberg, Kolseth, Steinberg, & Persson, 2017;Walder et al, 2017). Where taxa of particular interest are known from the start, use of taxon-specific marker genes may be desirable.…”

Classification of Fusarium-infected and healthy wheat kernels based on features from hyperspectral images and flatbed scanner images: a comparative analysis

“…Wheat kernels infected with fungi of the genus Fusarium appear shrivelled; they are lightweight, chalky and covered with mycelia with white or pink discoloration [9]. Fungi of the genus Fusarium cause cereal diseases such as Fusarium head blight (FHB) which decreases yields and has serious economic consequences [10]. FHB disease is caused by several Fusarium species, including mainly Fusarium graminearum, Fusarium culmorum, Fusarium avenaceum and Fusarium poae, as well as Fusarium equiseti, Fusarium langsethiae and Fusarium sporotrichioides.…”

“…Mycotoxin-contaminated grain is harmful for humans and animals, and it is not suitable for the production of food and feed [10]. Mycotoxins can cause diseases of the liver, kidneys, nervous system and immune system [12].…”