Hordeum jubatum: An alternative host for fungal pathogens attacking cultivated barley

Wild grasses can serve as hosts for plant pathogens that attack small grain cereal crops, thereby perpetuating the disease cycle and potentially initiating epidemics. Foxtail barley (Hordeum jubatum) is a perennial grass species that is common across North America and can often be found growing near cultivated barley fields. Despite the close proximity of the two plant species in agro-ecosystems, few studies have been advanced to characterize the compatibility of H. jubatum to barley pathogens and its possible role in disease epidemiology. The objective of this study was to assess whether H. jubatum can act as a host to seven fungal pathogens causing diseases of barley. A collection of H. jubatum accessions (N=100) collected from sites in Minnesota, Wisconsin, and North Dakota in the U.S. and Manitoba in Canada were inoculated at the seedling or adult plant stage in the greenhouse with isolates of Dreschlera teres f. teres (causal pathogen of net form net blotch), Bipolaris sorokiniana (spot blotch), Puccinia graminis f. sp. tritici (stem rust), Blumeria graminis f. sp. hordei (powdery mildew), Puccinia striiformis f. sp. hordei (stripe rust), Puccinia hordei (leaf rust) and P. coronati-hordei (crown rust). None of the accessions showed any visual signs of infection when challenged with B. graminis f. sp. hordei and P. hordei. In contrast, from 97% to 100% of evaluated accessions were infected by D. teres f. teres, B. sorokiniana, P. graminis f. sp. tritici, P. striiformis f. sp. hordei, and P. coronati-hordei. The relative degree of compatibility of H. jubatum to these latter five pathogens ranged from low (similar to resistant barley) to high (similar to susceptible barley). These results demonstrate that H. jubatum can be infected by isolates of important barley pathogens, but typically not with the same degree of compatibility as susceptible barleys. Nevertheless, when infected plants of H. jubatum are growing near barley fields, they could serve as reservoirs of inoculum to initiate some diseases.