Project Number: 500-42-001-67
Project Type: Grant

Start Date: Apr 01, 2004
End Date: Mar 31, 2005

Objective:
To determine whether symptom expression or yield, alone or in combination, can be used to distinguish between Verticillium wilt resistant and susceptible clones grown in early breeding generations; and to determine the efficiency of selecting resistant clones in families derived from conventional crosses versus unilateral sexual polyploidization.

Approach:
Hybrid families from the University of Minnesota potato breeding program, containing 15 clones each, will be used in this study. Each family will be planted in two replications of single hill units on each of two fields at the UW Agricultural Experiment Station. Clonal identity will be maintained throughout the trial. Field A is the Verticillium wilt resistance screening field. The second field (B) is a standard research plot with insignificant levels of the pathogen. In July and August, Verticillium wilt symptom expression will be scored for each plant in field A. Just prior to harvest, basal stem segments will be collected from each plant the number of V. dahliae colonies will be counted as a measure of stem colonization. At harvest, each plot in field A will be visually scored for yield. In addition, all tubers will be collected from each plot to provide an accurate measurement of yield. Once resistant clones have been identified based on yield loss and stem colonization, we will use the symptom expression data and visual estimations of yield to determine if either of these methods effectively identifies resistant clones. We will determine how effectively we could distinguish between resistant and susceptible clones (based on measured yield loss and stem colonization data) if we had used symptom expression as our selection criterion. In addition, we will determine what proportion of susceptible clones we would have eliminated by selecting against clones with low visual estimates of yield on field A. We will also be able to determine what proportion of resistant clones we would have selected against (erroneously) using this technique. By determining how many errors we would have made using each technique alone as a selection criterion, we will be able draw conclusions about the feasibility of each as a selection technique for breeders. Alternatively, both techniques may be employed simultaneously. We will determine whether we can improve our selection efficiency by eliminating the clones with high symptom expression and then selecting against low yield in the remaining clones. We will compare selection data from the 4x-4x families with those from 4x-2x families to determine whether resistant clones are more effectively selected using unilateral sexual polyploidization. Although parents will vary among the crossing schemes, an evaluation across all families may be able to identify trends with respect to uniformity of resistance and effectiveness of selecting resistant clones within each scheme.

Project Team

Bennett, A. Rick Shelley Jansky - Professor 301-504-6915

Related National Programs

Plant, Microbial & Insect Genetic Res., Genomics, & Genetic Improv. I (301)   Plant Diseases (303)