Variation in pathogen aggressiveness within a metapopulation of the Cakile maritima-Alternaria brassicicola host-pathogen association

• Published in: Plant pathology 2005-06, Vol.54 (3), p.265-274
• Main Authors: Thrall, P.H, Barrett, L.G, Burdon, J.J, Alexander, H.M
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Alternaria brassicicola; Biological and medical sciences; Brassicaceae; Cakile; Cakile maritima; disease epidemic; disease severity; epidemiology; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; fungal spores; Genetics and breeding of economic plants; host plants; host-pathogen relationships; lesion growth; lesions (plant); pathogen fitness; pathogenicity; Phytopathology. Animal pests. Plant and forest protection; plant pathogenic fungi; resistance; trade‐off; Varietal selection. Specialized plant breeding, plant breeding aims
• ISSN: 0032-0862; 1365-3059
• DOI: 10.1111/j.1365-3059.2005.01190.x

Variation in aggressiveness and its consequences for disease epidemiology were studied in the Cakile maritima–Alternaria brassicicola host–pathogen association. Variability in pathogen growth rates and spore production in vitro, as well as disease severity and lesion growth rate on C. maritima in glasshouse inoculation trials, were investigated. Substantial variation was found in growth rates among individual A. brassicicola isolates, as well as among pathogen populations. A significant trade‐off also existed between growth and spore production, such that faster‐growing isolates produced fewer spores per unit area. While there was little evidence for a link between growth in vitro and either disease severity or lesion development among fast‐ vs slow‐growth isolate classes at the individual isolate level, the results suggest that variation in pathogen fitness components associated with aggressiveness may influence disease dynamics in nature. An analysis using an independent data set of disease prevalence in the associated host populations found a significant positive relationship between the average growth rate of pathogen populations in vitro and disease progress over the growing season in wild host populations. Trade‐offs such as those demonstrated between growth rate and spore production may contribute to the maintenance of variation in quantitatively based host–pathogen interactions.