Abstract
Returning wheat residues to the soil is a common practice in modern agricultural systems and is considered to be a sustainable practice. However, the negative contribution of these residues in the form of “residue-borne pathogens” is recognized. Here, we aimed to investigate the structure and ecological functions of fungal communities colonizing wheat residues during the early phase of decomposition in a conventional farming system. The experiment was conducted under both ambient conditions and a future climate scenario expected in 50–70 years from now. Using MiSeq Illumina sequencing of the fungal internal transcribed spacer 2 (ITS2), we found that plant pathogenic fungi dominated (~87% of the total sequences) within the wheat residue mycobiome. Destructive wheat fungal pathogens such as Fusarium graminearum, Fusarium tricinctum, and Zymoseptoria tritci were detected under ambient and future climates. Moreover, future climate enhanced the appearance of new plant pathogenic fungi in the plant residues. Our results based on the bromodeoxyuridine (BrdU) immunocapture technique demonstrated that almost all detected pathogens are active at the early stage of decomposition under both climate scenarios. In addition, future climate significantly changed both the richness patterns and the community dynamics of the total, plant pathogenic and saprotrophic fungi in wheat residues as compared with the current ambient climate. We conclude that the return of wheat residues can increase the pathogen load, and therefore have negative consequences for wheat production in the future.
Highlights
Plant residues play important roles in nutrient dynamics and soil fertility in different types of agricultural ecosystems [1]
Our results indicate that the predicted climate changes, with alterations to temperature and precipitation patterns, can increase disease risks in agroecosystems, as under the future climate scenario applied in the Global Change Experimental Facility (GCEF) field experiment, five potential plant pathogenic fungi (Paraphoma rhaphiolepidis, Pyrenochaetopsis leptospora, Neostagonospora elegie, Blumeria graminis, and Waitea circinata) emerged but were not detected in plots under the ambient climate conditions
Our analyses showed a potentially high impact of climate change on fungal richness pattern and community dynamics in wheat residue at the early stage of decomposition
Summary
Plant residues play important roles in nutrient dynamics and soil fertility in different types of agricultural ecosystems [1]. Over time, we can expect strong microbial community dynamics and diverse ecological functions in plant residues Whilst some of these early microbial populations in residues prevent diseases or enhance plant growth, others cause different types of plant disease [9]. Residue return can be considered to be a causative agent for plant diseases, by providing pathogen inoculum and suitable conditions for pathogen growth, propagation, and accumulation, which results in epidemic diseases [2,7]. These complex microbial communities inhabiting plant residues have remained largely uncharacterized [12]. Recent studies, using generation sequencing (NGS), have greatly improved our understanding of the richness and composition of mycobiomes associated with plant residues [9,13,14,15,16,17,18,19], the approach has not yet been applied to investigate the fungal pathogen gains and their dynamics in plant residues
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