Objective: Determination of the concentration and species composition of filamentous fungi in root vegetables (carrots and red beetroots), and the adjacent rhizosphere soil, collected on organic and conventional farms in Eastern Poland.
Material and methods: During the period 2015-2016, a total number of 80 samples of vegetables and 40 samples of soil were examined. From each type of farm, 20 samples of vegetables and 20 samples of the adjacent soil were examined. In addition, the study included 20 samples of vegetables from organic farms and 20 samples of vegetables from conventional farms purchased on the markets in the city of Lublin in Eastern Poland. In order to determine the concentration and species composition of filamentous fungi, both in vegetables and soil, the method of plate dilutions on Malt Agar medium (Difco) with chloramphenicol was used. The study was conducted in two parallel repetitions. Inoculated media were incubated at the temperature of 30° C for 72 hours, then at room temperature for 72 hours. The species composition of fungal flora was determined using macroscopic and microscopic methods, with the help of keys and atlases.
Results: It was found that the mean concentration of fungi was higher in vegetables and soil from conventional farms than in those from organic farms. In the case of carrots and soil from conventional farms, this concentration was 4.93 and 5.10 log10 CFU g-1, respectively, whereas from organic farms - respectively, 3.81 and 4.20 log10 CFU g-1. In the case of beetroots and soil from conventional farms, the mean concentrations were also higher compared to organic farms - 5.09 vs. 3.93 and 4.95 vs. 4.23 log10 CFU g-1. In the examined vegetables and rhizosphere soil, 61 species of filamentous fungi were found, of which 12 belonged to the genus Penicillium, 4 to the genus Fusarium, and 2 species each to the genera: Aspergillus, Cladosporium and Trichoderma. As many as 28 (45.9%) fungal species that occurred in vegetables and soil are regarded as pathogenic for humans.
Keywords: filamentous fungi; organic and conventional farms; rhizosphere soil; vegetables.