Aerobiological aspects of quarantine risks in grain warehouses: a study on bunt (Tilletia spp.) dispersal

Abstract

Several countries refuse the import of wheat if it is contaminated with Tilletia spp. Local quarantine regulations are in effect regarding Tilletia indica and Tilletia controversa as part of a strategy to first hinder the disease from establishing in the country or eradicate the disease and, more recently, to prohibit the spread of it. Because of the economic importance of these fungal pathogens in the warehouses, the aerobiology of Tilletia spp. should be known better. Air (with a portable Hirst-type volumetric impaction sampler) and wheat seeds were collected in two central grain warehouses in Budapest (Bp) and Jaszapati (Ja) and in 14 farm warehouses. Quarantine organisms (T. controversa and T. indica) were not detected in any of the samples. Tilletia caries dominated in the air and seed samples, while Tilletia laevis were present only in a low concentration in the samples collected in Bp, but this fungus was absent in both Ja and the farm warehouses. Teliospore levels of the two different sites of wheat storage rooms in Bp were compared, but no significant difference was found between them (p = 0.16). Similarly, the volume of stored wheat did not significantly affect the Tilletia spp. concentrations (p = 0.46) in the air. Teliospore levels in seed samples correlated with those in the air samples which were collected from above the wheat heaps (r = 0.596, p < 0.05). In Bp, teliospore dispersal takes place rapidly between storage rooms and floors via open-top walls and spouts, respectively. Consequently, there is a higher risk of contamination because of the high teliospore concentration in the air and the high probability of teliospore dispersal. It is proposed that warehouses could be tested for quarantine or economically important Tilletia spp. not only by seed sampling but by aerobiological methods as well. Our results claim attention on the quarantine risk of airborne contamination with Tilletia spp. teliospores of grain warehouses, and some modification in control strategy against warehouse contamination is suggested.