Breeding for Root Lesion Nematode Resistance in Montana Winter Wheat.

The root lesion nematode Pratylenchus neglectus represents a significant constraint on Montana winter wheat production, causing an estimated average annual yield loss of 12.9%.  The development of nematode-resistant winter wheat cultivars is therefore highly desirable for growers, and is the goal of this project. In February 2012, a greenhouse disease screening was conducted, consisting of 200 BC₁ F₃ (Yellowstone*2/Persia 20) progeny along with the parent plants, the resistant landrace “Persia 20” and susceptible elite hard red winter wheat cultivar “Yellowstone.” Each entry was planted in a 2-inch conetainer and inoculated with an average of 68 nematodes/cone. After 18 weeks, nematodes were extracted from soil and counted under the microscope.  Final populations averaged 148 nematodes/cone and ranged from 11 to 643 nematodes/cone.  ANOVA failed to detect differences among entries (p = 0.20). Significant differences were detected between resistant parent Persia 20 and susceptible parent Yellowstone (p = 0.03).  A second screening was initiated in November 2012 using a subset of 55 BC₁F₄ lines (28 resistant and 27 susceptible) selected based on initial data. Plants were inoculated with an average of 155 nematodes/cone. ANOVA again failed to detect significant differences among selected lines (p = 0.15). Notably, Yellowstone averaged 325 nematodes/cone and Persia 20 averaged 408 nematodes/cone, with no significant difference between them (p = 0.49).  A third resistance screening, using seed derived from the 55 BC₁F₄ lines, was begun in May 2013 and used inoculum confirmed as P. neglectus with species-specific PCR markers. As genetic markers linked to nematode resistance will greatly increase selection efficiency, DNA from the selected lines was extracted and genotyped using single nucleotide polymorphism (SNP) markers identified as variable between parental lines.  The marker data will be compared with screening data to identify markers that co-segregate with nematode resistance, thereby aiding the introgression of resistance genes in a backcross breeding regime.