Serological Detection of Spongospora Subterranea F.SP. Subterranea in Soil

Abstract

A bioassay with tomato as bait plants was compared with detection by ELISA using a dilution series of spore balls in uncontaminated soil. The relationship between A₄₀₅ values and spore ball concentration/g soil appeared to be linear and raw antiserum detected down to 100 spore balls/g soil. Discrimination of spore ball levels improved with concentrations above 2000/g soil, whereas the bioassay showed better discrimination of spore ball levels below 2000/g soil. When a range of soils from Swiss potato fields with known bioassay scores were tested by ELISA, raw serum discriminated most of the soils with higher scores (≥ 3) from those with lower scores, but not between uncontaminated and infested soils with lower scores (<3). Of the three soils with scores higher than 3, the two where high tuber disease indexes were obtained also gave highest A₄₀₅ values. The ability of the antiserum to discriminate infested field soils from uncontaminated ones was much improved by using the γ-globulin fraction, or serum which had been cross-absorbed with uncontaminated soil. The results are discussed and advantages and disadvantages of both detection methods compared.