Fungal contamination in barley and Kashin-Beck disease in Tibet

Abstract

5First results showed that mesophilic fungal contaminations were significantly higher on barley grains stored in families with KBD (median 66% of grains infected) than in healthy families (median 43% of grains infected) (Kruskal-Wallis p<0·01). The risk of KBD associated with the presence of fungal taxa on barley grains was expressed in odds ratios (ORs), adjusted for age and sex and calculated with logistic regression. Three common fungal taxa in grains were significantly associated with KBD. Trichothecium roseum (Pers) Link ex Gray (OR16·37, p<0·001), Dreschlera Ito (OR8·75, p<0·001) and Alternaria Nees ex Fr (OR2·96, p<0·001). ORs adjusted for the presence of other fungi concerned showed an independent effect of each of these three taxa. However the effect of Dreschlera was significantly higher in presence of a fourth taxon. Cladosporium Link ex Fr, indicating an interaction (p<0·05). Compared with the absence of fungi, the cumulative effect of different fungal associations can be estimated (figure). On the basis of these results, we conclude that, in Tibet, there are two critical periods for fungal grain contamination related to KBD. First, during the growing season, from contaminated seeds (Dreschlera) or from contaminated debris of the preceding harvest (Alternaria, Cladosporium). Second, just after harvest, during the drying period in the field, especially when the daily difference of temperature is high (dewy grains) and consequently, at the beginning of the storage, when too moist grains are placed in bags or other containers (Trichothecium roseum and also Alternaria and Cladosporium). As measures to prevent KBD in Tibet, we suggest disinfection of barley seeds, destruction of crop residues, and efficient grain drying before storage.