Adaptation of Phytopathogenic Fungi to Quantitative Host Resistance: In Vitro Selection for Greater Aggressiveness in Fusarium Head Blight Species on Wheat

• Published in: Cytology and genetics 2022-06, Vol.56 (3), p.261-272
• Main Author: Sakr, Nachaat
• Format: Article
• Language: English
• Subjects: Aggressiveness; Biomedical and Life Sciences; Biomedicine; Crop production; Cultivars; Dextrose; Fusarium; Fusarium head blight; Growth rate; Human Genetics; Latent period; Pathogens; Phytopathogenic fungi
• ISSN: 0095-4527; 1934-9440
• DOI: 10.3103/S0095452722030112

Fusarium head blight (FHB) is a global significant threat to crop production in small grains such as wheat. Till recently, we still lack empirical data on the selective effects of wheat quantitative resistance on aggressiveness changes in diverse FHB pathogens which may lead to potential resistance erosion because of the difficulty of conducting such studies under field conditions. Four FHB causative agents were used to study the evolution of aggressiveness using in vitro serial passage assays on susceptible “S” and moderately resistant “MR” wheat cultivars. These pathogens were previously tested and were found to be highly aggressive in vitro. Differences due to the selective impact of a cultivar among non-selected and selected isolates were measured for traits contributing to parasitic (latent period (LP) and area under disease progress curve (AUDPC)) and saprophytic (growth rate) fitness. The pathogen populations evolved faster on “MR” cultivars than “S” cultivars. Selected isolates were significantly more aggressive than non-selected isolates for LP and AUDPC, while no increase in aggressiveness was found on potato dextrose agar, indicating that the evolution of aggressiveness in FHB agents is associated with the presence of wheat plants with contrasted resistance levels. Selected isolates from “MR” cultivars were more aggressive than selected isolates from “S” cultivars, as they had a shorter LP (48.8%) and a higher level of AUDPC (18.4%). These results provide the first direct evidence that FHB pathogens adapt to wheat by increasing aggressiveness, suggesting a risk of directional selection and possible erosion of FHB resistance, an essential element for the development of durable management strategies for resistant wheat cultivars to FHB infection.