The effect of wheat resistance on the aggressiveness on Fusarium graminearum

Fusarium graminearum is a causal agent of Fusarium Head Blight (FHB) on wheat. Not only does this disease cause significant yield and quality losses but the pathogen also produces mycotoxins. The most common mycotoxin produced by F. graminearum during the infection of wheat is deoxynivalenol (DON). Globally wheat is the most extensively grown cereal crop and is an important source of nutrition around the world. F. graminearum also has a worldwide distribution and is responsible for billions of US dollars in losses. Genetic host resistance is the most effective way to control FHB and has the potential to be both durable and consistent. Little is known about the effect wheat resistance to FHB has on the aggressiveness of F. graminearum. It is theorized that a susceptible host allows for higher pathogen genetic variance, leading to rapidly increasing aggressiveness through positive selection. On a susceptible host, the more aggressive isolates are better able to outcompete the other isolates, increasing the aggressiveness of the F. graminearum population on susceptible wheat varieties. To determine if host resistance is a durable method of FHB control it is important to understand if resistant wheat varieties are selecting for more aggressive F. graminearum isolates. Plant pathogen aggressiveness is the quantitative variation of disease signs and symptoms on susceptible hosts. In F. graminearum, aggressiveness is a highly variable and heritable trait. To understand the effect of host resistance on F. graminearum aggressiveness, research was completed using 31 F. graminearum isolates collected from susceptible wheat and 25 isolates collected from resistant wheat varieties. The isolates were phenotyped through in vitro assays and greenhouse in planta assays. The in vitro growth rate and spore production were measured. In the greenhouse assays, three disease severity ratings were taken over time and used to calculate AUDPC. After kernels were harvested, Fusarium Damaged Kernels (FDK) were measured. Next, the amount of DON present in the kernels was quantified. Genotypic analysis was also executed on the 56 F. graminearum isolates. DNA was extracted and sequenced from the 56 F. graminearum isolates to create a SNP data set. Phylogenetic analysis and a whole genome scan for selection was performed using the SNPs. The results from the phenotypic analysis found that isolates from a susceptible source were more aggressive than isolates from a resistant source. The majority of isolates from a highly susceptible host were strong while there was an even mixture of aggressiveness among the isolates from a moderately resistant host. This means that resistant wheat varieties are not selecting for more aggressive F. graminearum isolates and in fact the highly susceptible host is selecting for aggressive isolates. The phylogenetic analysis looked at the relationship between the 56 F. graminearum isolates and found no clustering due to host resistance or due to pathogen aggressiveness. The whole genome scan for selection identified fourteen genes under selection in the population from highly susceptible wheat and seven genes under selection in the population from moderately resistant wheat. Several of these genes that were under selection were found to be related to pathogen aggressiveness. These genomic results support the phenotypic results, that a highly susceptible host allows more pathogen reproduction increasing the amount of variation that selection can act on leading to an overall increase of aggressiveness in the population.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Krone, Mara Jeanne

Contributors dc:contributor

• Mideros, Santiago X

• Wheat resistance
• Fusarium head blight
• Wheat scab
• Pathogen aggressiveness
• Fusarium graminearum
• Fusarium population genetics
• Mycotoxins
• Deoxynivalenol
• Phylogenetics
• Quantitative host resistance
• Plant pathogen interaction

Statement dc:rights

• Copyright 2022 Mara Krone

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115934

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115934