Spring Wheat Tolerance and Resistance to Heterodera avenae in the Pacific Northwest

Abstract

Smiley, R. . 2013. Spring wheat tolerance and resistance to Heterodera avenae in the Pacific Northwest Plant Dis 97-590-600.The cereal cyst nematode Heterodera avenae reduces wheat yields in the Pacific Northwest. Previous evaluations of cultivar resistance had been in controlled environments. Cultivar tolerance had not been evaluated. Seven spring wheat trials were conducted in naturally infested fields in three states over 2 years. A split-plot design was used for all trials. Five trials evaluated both tolerance and resistance in 1.8-by-9-m plots treated or not treated with nematicides. Two trials evaluated resistance in l-m head rows where each wheat entry was paired with an adjacent row of a susceptible cultivar. Cultivars with the Crel resistance gene ('Ouyen' and 'Chara') reduced the postharvest density of H. avenae under field conditions, confirming Crel parents as useful for gennplasm development. Ouyen was resistant but it was also intolerant, producing significantly lower grain yield in controls than in plots treated with nematicides. Susceptible cultivars varied in tolerance. Undefined resistance was identified in one commercial cultivar ("WB-Rockland) and four breeding lines (UC1711. SO900163. SY-B()41418, and SY-97621-05). This research was the first systematic field demonstration of potential benefits to be derived through development and deployment of cultivars with resistance plus tolerance to cereal cyst nematode in North America.

Discovery of Heterodera filipjevi in Washington and Comparative Virulence with H. avenae on Wheat

“…avenae was first detected in the United States in 1974, in western Oregon (20), and is now reported in seven western states that include the Pacific Northwest (PNW) states of Idaho, Oregon, and Washington (43). H. avenae has reduced yields of susceptible wheat cultivars by as much as 64% (43,46,48,50) and is estimated to reduce the profitability of wheat production by at least $3.4 million annually in the PNW (43).…”

“…Wheat is therefore produced mostly in 2-year rotations that do not ade quately suppress the nematode density before the next crop of susceptible wheat is planted. Spring wheat cultivars with resistance to H. avenae were recently identified (47,48), but resistance to H. filipjevi has not been evaluated in the PNW. Research in other countries indicated that individual wheat cultivars may differ in their ability to serve as hosts of these two nematodes; cultivars resistant to H. avenae may not be resistant to H. filipjevi, and vice versa (29).…”

“…In April 2014, the authors of this paper received a fresh sample of H. avenae from a field in Washington that had not been included in our earlier laboratory, greenhouse, and field studies with popula tions of H. avenae (48,52,65,67). The sample consisted of soil containing dislodged brown cysts and wheat stubble in which white females remained embedded in roots.…”

“…Soils were not sampled in northeast Whitman County because previous research had shown four populations of Heterodera spp. from that region to be H. avenae, including fields near Cashup, Colfax, Palouse, and Steptoe (48,52,65,67). Sampling sites were selected to meet one or more of the following criteria: (i) sites near State Route 26, between the towns of Dusty and Colfax, where H. avenae had been previously confirmed (67); (ii) sites near U.S. Route 195, between Colfax and Uniontown, where public-or pri vate-sector wheat or pulse cultivar research trials had been located, as observed using Google Earth version 7.1.2.2.2041 imagery data dated 4 July 2013, 5 July 2013, and 24 July 2013, and including the wheat cultivar screening trial from which the initial sample had been collected (reported previously as Figure 4 in Smiley et al [48]); or (iii) sites south of Uniontown near the location where an infestation of 'H.…”

“…These samplings were in low-lying areas of fields near the northward-flowing Union Flat Creek. Additionally, one sample was collected north of Pullman, where H. avenae was suspected of being the only Heterodera species present (reported previously as Figure 3 in Smiley et al [48]). Samples were col lected and processed as described previously for quantifications by Western Laboratories and for species identification by our labora tory.…”