Ecology of the Ochratoxin A ProducingPenicillium verrucosum:Occurrence in Field Soil and Grain with Special Attention to Farming System and On-Farm Drying Practices

Abstract

ABTRACTMycotoxin contamination of organically grown cereals has been a growing concern during recent years, one of the most important being ochratoxin A (OTA). In countries with a temperate, humid climate, OTA is produced by Penicillium verrucosum and it is crucial to focus on the fungus to obviate problems. This paper presents results to elucidate different aspects of the ecology of P. verrucosum. In a survey of differently farmed soils, P. verrucosum was found in 11 out of 65 soils, 35% of the organically and 7% of the conventionally cultivated, these being the first reports of its natural occurrence in soil. Except for two soils, it was found with low frequencies (100-300 cfu g dry soil-1 ), and the results point to home grown seed as a potential risk of soil contamination. In a survey of organically grown grain, P. verrucosum was found in 51% of the recently combined and not yet dried grain samples; 60% of the rye and 53% of the wheat samples. This confirms that early contamination does take place and increases the demand for proper grain handling during drying and storage. Three case studies were performed at organic farms with different storage facilities. The results showed very clearly that there is no general risk of OTA contamination in organically cultivated grain. Within the same year, major differences between the farms were found and these differences were reproduced during three growing seasons. It therefore seems likely that an organic farming system, as such, does not present problems in relation to OTA contamination. It is, rather, certain management practices that are inappropriate and these management practices may be more prevalent in organic farming. This assumption is discussed in relation to home grown seed, crop rotation, organic fertilizers, exclusion of pesticides, and drying and storage facilities.

Penicillium verrucosum occurrence and Ochratoxin A contents in organically cultivated grain with special reference to ancient wheat types and drying practice

“…In 1998, Elmholt [8] analysed 35 combined samples from 15 farmers and found 51% of the samples to be contaminated by P. verrucosum (median 0.6%, maximum 5.8%). Thus, the combined samples from the present study had more contaminated samples and higher mean contamination levels ( Table 4).…”

“…Considering the many contaminated kernels, this risk should be taken seriously especially if the grain is harvested at a high MC as discussed below. The origin of early contamination is not fully understood but some soils contain P. verrucosum [8] and P. verrucosum conidia can survive in soil for many months [17]. Miller [9] pointed out that the combine may act as an efficient disseminator of fungal conidia within a batch of harvested grain and that infestation of some kernels by ochratoxigenic P.…”

“…However, most problems seem related to insufficient drying facilities at small farms, which at least some years ago were more prevalent in organic farming [7][8]. A number of studies and surveys have shown differences in OTA susceptibility among the small grain cereals [6][7]10].…”

“…Danish producers and processors of organically grown cereals have been especially concerned about OTA contamination because a number of studies indicate OTA problems to be more prevalent in organic than conventional farming [6][7][8]. Quality criteria are crucial in organic production and one such criterion is the avoidance of toxic residues in cereal commodities.…”

Characterization of the Relationships between Wheat Cultivars, Fusarium Head Blight, and Mycoflora Grains

“…Contamination may therefore occur at any moment between anthesis and storage, refl ecting the composition of the mycofl ora residing in the environment of the plant [4]. Environmental factors such as the presence of determined fungal species, humidity, wind, and other climatic factors also infl uence the colonization of grains with fungi.…”