Candidate Genes for Aggressiveness in a Natural Fusarium culmorum Population Greatly Differ between Wheat and Rye Head Blight

Abstract

Fusarium culmorum is one of the species causing Fusarium head blight (FHB) in cereals in Europe. We aimed to investigate the association between the nucleotide diversity of ten F. culmorum candidate genes and field ratings of aggressiveness in winter rye. A total of 100 F. culmorum isolates collected from natural infections were phenotyped for FHB at two locations and two years. Variance components for aggressiveness showed significant isolate and isolate-by-environment variance, as expected for quantitative host-pathogen interactions. Further analysis of the isolate-by-environment interaction revealed the dominant role of the isolate-by-year over isolate-by-location interaction. One single-nucleotide polymorphism (SNP) in the cutinase (CUT) gene was found to be significantly (p < 0.001) associated with aggressiveness and explained 16.05% of the genotypic variance of this trait in rye. The SNP was located 60 base pairs before the start codon, which suggests a role in transcriptional regulation. Compared to a previous study in winter wheat with the same nucleotide sequences, a larger variation of pathogen aggressiveness on rye was found and a different candidate gene was associated with pathogen aggressiveness. This is the first report on the association of field aggressiveness and a host-specific candidate gene codifying for a protein that belongs to the secretome in F. culmorum.

Be flexible and adapt easily—The great role of plasticity relative to genetic variation for aggressiveness of Fusarium culmorum isolates

“…In the cereal– Fusarium pathosystem, a key factor that determines the parasitic fitness of an isolate is aggressiveness, which is a quantitative measurement of the level of disease caused by the pathogen (Pariaud et al, ; van der Plank, ). Aggressiveness is frequently evaluated by directly assessing symptom development at different time points (=epidemic rate) (Castiblanco, Castillo, & Miedaner, ; Miedaner & Schilling, ; Miedaner, Gang, & Geiger, ; Pariaud et al, ). It reflects several basic quantitative traits of the fungal life cycle, such as infection efficiency, spore production rate, sizes of the lesion and for some cases, also toxin accumulation (Cumagun & Miedaner, ; Lannou, ).…”

“…Aggressiveness is of complex inheritance with many genes, each contributing only to a small part of the total variation. Recently, a candidate gene‐based association study reported an association of mitogen‐activated protein kinase (MAPK) HOG1 gene with aggressiveness and deoxynivalenol (DON) accumulation, explaining 10.29 and 6.05% of the genotypic variance in wheat, respectively, and of a cutinase gene explaining 16.05% of genotypic variance in rye (Castiblanco et al, ; Castiblanco, Marulanda, Würschum, & Miedaner, ). The role of DON in the different phases of the Fusarium life cycle (e.g.…”

Aggressiveness profiling of the coffee pathogen Colletotrichum kahawae

“…The IDI_10dai is a quantitative trait that is easier to measure (only one time point) and, due to its high correlation with AUDPC, can be considered a highly efficient aggressiveness trait that could be applied in future studies. The latent period is also one of the most used aggressiveness quantitative traits in the literature, and provides important information regarding isolate adaptation, as isolates with shorter latent period have a selective advantage in the field, by quickly releasing the conidia into the environment (Pariaud et al, 2009a;Fr ezal et al, 2012;Delmas et al, 2016). The latent period is sometimes considered identical to the incubation period (Luo & TeBeest, 1997).…”

“…For several plant pathogen species, aggressiveness is a polygenic quantitative trait, influenced not only by the host genotype but also by the environment (e.g. temperature and humidity; Boedo et al, 2012;Delmas et al, 2016), and therefore it is considered to be shaped by natural selection resulting in different adaptive patterns according to the environment (Pariaud et al, 2009b(Pariaud et al, , 2012Boedo et al, 2012;Delmas et al, 2016). A quantitative adaptation to the host is theoretically expected to be slower than the acquisition of new qualitative virulence factors (Pariaud et al, 2009b).…”

“…A quantitative adaptation to the host is theoretically expected to be slower than the acquisition of new qualitative virulence factors (Pariaud et al, 2009b). Therefore, it is necessary to gather empirical knowledge on the nature of pathogen aggressiveness, as well as its genetic and environmental determinants, and on the ability of pathogens to respond to the selective pressures imposed by host quantitative resistance (Pariaud et al, 2009b;Delmas et al, 2016). In this study, similar to that described in other plant pathogen interaction studies (Boedo et al, 2012;Pariaud et al, 2012;Purahong et al, 2012), 'aggressiveness' will be considered as the quantitative measurement of the level of disease reached over time.…”