Epsilon Archive for Student Projects

Abstract

Aphanomyces euteiches is a soil-borne pathogen that causes major yield losses in pea cultivation in Sweden. The lack of preventative measures emphasizes the importance of disease forecasting. So far, this has been done in the form bioassays, in which soil was taken from fields to be studied and peas were grown in the greenhouse on a trial basis. Molecular analysis using ddPCR is a potential alternative. In this study, it was investigated whether the amount of A. euteiches gene copies per gram of naturally infested soil correlates with the disease index of the peas determined in the bioassay. However, this could not be confirmed. The experiment was conducted in two parts and Spearman’s correlation coefficient between the number of gene copies and the disease index was 0.11 and 0.18, indicating no statistically significant correlation. Among the main reasons for the lack of an expected correlation between the disease index and the quantity of A. euteiches DNA in the soil was the fact that the naturally infested soil potentially contains a range of pathogens that can cause similar symptoms and can influence each other's infectivity. In addition, it was investigated whether grinding the soil leads to improved A. euteiches detection. It was anticipated that soil grinding would enhance DNA extraction, improve homogeneity and aid in accessing A. euteiches DNA by cracking the oospores outer shell. Grinding the soil did not increase or stabilise the DNA yield, nor did it improve the detection of A. euteiches DNA. Among the suggested reasons for this is that the soil homogenisation during the DNA extraction process is sufficient and that the large amount of soil extracted (10 g) used for DNA extraction led to a decrease in variability between the samples.