The effect of cultivar used as host for Polymyxa gmminis on the multiplication and transmission of barley yellow mosaic virus (BaYMV)

SUMMARY A viruliferous isolate of the fungal vector Polymyxa graminis was grown on roots of barley cultivars immune or susceptible to barley yellow mosaic virus (BaYMV). Zoospores or resting spores of the vector produced on different cultivars were then inoculated to a virus‐susceptible test cultivar. Although the vector established in all treatments, transmission of BaYMV was rare and usually nil from immune cultivars; amounts of virus detected serologically in their roots were very low, thus showing that resistance was to virus multiplication. If immune cultivars decrease the virus content of vector populations in the field, this would have important implications for disease control.