Epsilon Archive for Student Projects

Abstract

Aphanomyces euteiches, A. cochlioides, and A. cladogamus are three devastating agricultural plant pathogens that respectively are causing diseases such as pea root rot, sugar beet root rot, and spinach root rot. This study aims to investigate the distribution of the three Aphanomyces species in parts of Sweden, Denmark, and Lithuania. It also aims to analyse macronutrient levels in the soil and explore potential connections between these soil factors and the pathogen presence. Methods of the study involve conducting biotests collected from the different regions and evaluate the presence of Aphanomyces spp. Additionally, a large data set from biotests conducted in commercial pea growing in Sweden was analysed.
The study revealed differences in the occurrence of Aphanomyces spp. between regions. Aphanomyces euteiches was the most widespread pathogen found in 31% of the tested samples and in 8 out of 13 totally tested regions. Aphanomyces cochlioides had a more limited distribution and was found in 14% of the investigated samples and in 4 out of 13 regions. Aphanomyces cladogamus displayed intermediate distribution in Sweden and was present in 12% of the tested samples, and in 5 out of 13 regions. Aphanomyces euteiches only affected pea plants. However, an overlapping host range was observed between A. cochlioides and A. cladogamus, which infected both sugar beet and spinach.
Furthermore, results showed significant differences in values of disease severity index between regions, pathogens, and for the interaction between region and pathogen. Soil analysis from all the soil samples showed that the calcium content (Ca-AL) ranged from 82 to 3600 mg/100g dry soil. When Ca-Al levels were above 250 mg/100 mg soil no species of Aphanomyces was detected, indicating disease suppressiveness. Similar results were observed from the commercial pea growing data set; no DSI values above 20 (with A. euteiches) was found in any soil sample with a Ca-AL value above 210 mg/100 g soil. Combined DSI data from regions was plotted against the combined data for soil properties and tested for correlations. Results from this analysis showed that high Ca-AL levels correlated significantly (P ≤ 0.043) with low DSI levels in both pea, spinach, and sugar beet.
Currently, pesticides against Aphanomyces spp. are very limited, highlighting the need to understand the distribution patterns and the relationship between macro nutrients and the pathogens for better disease management.