ABSTRACT
Fusarium root and crown rot (FRCR) negatively impact several economically important plant species. Cover crops host different soil and residue microbiomes, thereby potentially influencing pathogen load and disease severity. The carryover effect of cover crops on FRCR in barley and soybean was investigated. Field trials were conducted in Prince Edward Island, Canada. Two cover crops from each plant group, including forbs, brassicas, legumes, and grasses, were grown in a randomized complete block design with barley and soybean planted in split plots the following year. Barley and soybean roots were assessed for FRCR through visual disease rating and Fusarium spp. were isolated from diseased tissue. Fungal and bacterial communities in cover crop residues were quantified using amplicon sequencing. The disease-suppressive effects of soil were tested in greenhouse studies. The results indicated that sorghum-sudangrass-associated microbiomes suppress Fusarium spp., leading to reduced FRCR in both barley and soybean. The oilseed radish microbiome had the opposite effect, consequently increasing FRCR incidence in barley and soybean. The results from this study indicate that cover crop residue and the associated soil microbiome influence the incidence and severity of FRCR in subsequent crops. This information can be used to determine cover cropping strategies in barley and soybean production systems.
ABSTRACT
Fusarium graminearum, a filamentous fungus, and causal agent of Fusarium head blight (FHB) in wheat and other cereals, leads to significant economic losses globally. This study aimed to investigate the roles of specific genes in F. graminearum virulence using CRISPR/Cas9-mediated gene deletions. Illumina sequencing was used to characterize the genomic changes due to editing. Unexpectedly, a large-scale deletion of 525,223 base pairs on chromosome 2, comprising over 222 genes, occurred in two isolates. Many of the deleted genes were predicted to be involved in essential molecular functions, such as oxidoreductase activity, transmembrane transporter activity, hydrolase activity, as well as biological processes, such as carbohydrate metabolism and transmembrane transport. Despite the substantial loss of genetic material, the mutant isolate exhibited normal growth rates and virulence on wheat under most conditions. However, growth rates were significantly reduced under high temperatures and on some media. Additionally, wheat inoculation assays using clip dipping, seed inoculation, and head point inoculation methods were performed. No significant differences in virulence were observed, suggesting that these genes were not involved in infection or alternative compensatory pathways, and allow the fungi to maintain pathogenicity despite the extensive genomic deletion.
