Inheritance of resistance to covered smut [Ustilago hordei (Pers.) Lagerh.] in barley

Covered smut of barley, caused by Ustilago hordei, has the potential to cause significant losses under organic production systems, particularly for hulless barley. The objectives of this investigation were to identify sources of resistance to covered smut and to study the inheritance of resistance and allelic relations between resistant barley lines. Hulled barley breeding lines and cultivars TR640, Q21861, TR244, and CDC Helgason were identified as sources of resista ice to covered smut based on screening for 3-5 yr in the field and twice in the greenhouse. No hulless sources with strong resista ice were identified indicating that there is a need to transfer resistance to hulless barley. Inheritance of covered smut resistance in the hulled barley line TR244 was studied using a hulless x hulled barley population screened with a mixture of U. hordei isolates. A single major resistance gene was identified in TR244. Many hulless lines in this population showed good resistance to covered smut indicating that resistance can be transferred to hulless lines. Allelic studies indicated that the resistance gene in TR244 is different from that in the resistant lines Q21861 and TR640.