Forty-three cultivars of durum wheat (Triticum durum Desf.) were grown during the 1998–99 growing
season in a field near Rome with natural inoculum sources of Soilborne wheat mosaic virus (SBWMV) and Wheat
spindle streak mosaic virus (WSSMV), to evaluate their resistance to the mixed infection. Leaf extracts from twelve
cultivars had relatively low ELISA values for WSSMV, and thirteen had low ELISA values for SBWMV. Results
confirmed the high level of resistance to SBWMV of the cultivars Colorado, Ionio and Neodur. The reactions of the
cultivars to SBWMV were consistent with those recorded in previous trials near Bologna, northern Italy, indicating
that the SBWMV strains at the two test sites were pathogenically similar. Disease severity was significantly correlated
with grain yield, thousand-kernel weight, heading date and the SBWMV-ELISA value, but not with the WSSMVELISA
value. Regression analysis showed that, as a result of the mixed infection, the four cultivars with the most
severe disease symptoms headed about 5 days later than normal, and suffered grain yield and kernel weight reductions
of about 56 and 10% respectively. Cultivars with milder symptoms were also severely affected