Resistance of wheat, barley and oat to Heterodera avenae in the Pacific Northwest, USA

Abstract

Abstract The cereal cyst nematode, Heterodera avenae, occurs in at least seven western states of the USA and reduces grain yield in localised regions and in selected crop management systems. Virulence phenotypes for H. avenae populations in North America have not been reported. Nine individual assays in six experiments were conducted to determine the reactions of barley, oat and wheat cultivars to five H. avenae populations in the Pacific Northwest (PNW) states of Idaho, Oregon and Washington. Three populations were evaluated for virulence to 23 entries of the 'International Test Assortment for Defining Cereal Cyst Nematode Pathotypes', plus selected local cultivars and entries representing a greater diversity of resistance genes. The virulence phenotype(s) for populations of H. avenae in the PNW did not correspond to any of the 11 pathotypes defined by the Test Assortment. Five PNW populations exhibited affinities with Group 2 but were not defined by pathotypes Ha12 and Ha22. Reproduction was prevented or greatly inhibited by barley carrying the Rha3 resistance gene and by most carriers of Rha2 resistance, and by selected oat cultivars with multigenic resistance. Wheat cultivars carrying the Cre1 resistance gene were highly effective in suppressing H. avenae reproduction. Current PNW wheat cultivars do not carry the Cre1 resistance gene. Crosses between Ouyen, an Australian bread wheat with Cre1 resistance, and several PNW wheat cultivars were resistant. The CreR gene also prevented H. avenae reproduction in the trial where it was tested. Intermediate levels of reproduction occurred on wheat cultivars carrying the Cre5, Cre7 and Cre8 resistance genes, each of which was considered useful for pyramiding into cultivars with Cre1 resistance. This research identified genetic resources of value in PNW cereal crop breeding programmes.