Distribution of Cereal Cyst Nematodes (Heterodera avenae and H. filipjevi) in Eastern Washington State

Abstract

Cereal cyst nematodes (CCN; Heterodera avenae and H. filipjevi), cause substantial worldwide yield loss in small grain cereals such as wheat, barley, and oat. H. avenae was first detected in the United States in western Oregon in 1974 and had spread to northeast Oregon by the mid-1980s. Although H. avenae was detected in eastern Washington in 1984, extensive infestations were not recognized until 2010. H. filipjevi, first detected in Oregon in 2008, was found in eastern Washington in 2014. To gain more information about the distribution of these two species, an extensive survey was undertaken in eastern Washington, and methods were developed to distinguish species using DNA sequencing of single cysts. In this study, we surveyed 356 wheat and barley fields in eastern Washington from 2007 to 2017. CCN from the infested locations were identified to species level by sequencing the ribosomal internal transcribed spacers (ITS) and/or 28S ribosomal RNA (rRNA) genes. The sequences were compared in the GenBank database in the National Center for Biotechnology Information (NCBI) to identify species. The results show that H. filipjevi is primarily confined to southern Whitman County, WA; and H. avenae has a wider distribution across the higher precipitation annual cropping area of eastern Whitman County. Knowledge of species identification is critical for deployment of host resistance as an effective means of management, since resistance genes for one species of CCN may not be effective against the other.