2008 National Potato Late Blight Trials
K.G. Haynes, USDA-ARS, Beltsville, MD 20705
C.A. Thill and J.M. Bradeen, Univ. of Minnesota, St. Paul, MN 55108
G.A. Secor, North Dakota State Univ. Fargo, ND 58105
M.I. Vales, Oregon State Univ., Corvallis, OR 97331
B.J. Christ and Xinshun Qu, The Pennsylvania State Univ., University Park, PA 16802
D.S. Douches, Michigan State Univ. East Lansing, MI 48824.
Materials and Methods
In 2008, 40 potato clones (4 varieties, 32 selections, 4 LB differentials) were evaluated in the field for foliar late blight at five U.S. locations: East Lansing, MI; Rosemount, MN; Prosper, ND; Corvalis, OR; and, Rock Springs, PA. Plots were planted in a randomized complete block design with 3-4 replications per location.
All five locations inoculated the plots with Phytophthora infestans. MI inoculated with isolates of US-1, US-6, US-8, US-10, US-11, and US-14. All other locations inoculated with isolates of US-8. In addition to US-8, an as yet unidentified isolate was found naturally in ND. Irrigation was applied as needed to provide conditions favorable for disease expression.
Percent infected foliage was recorded several times following onset of the disease. Area under the disease progress curve (AUDPC) was calculated (Shaner and Finney, 1977). At each location, clonal mean AUDPCs were ranked from 1 (lowest mean AUDPC) to 40 (highest mean AUDPC). The rankings of these AUDPCs were analyzed over all locations using nonparametric analysis of mean absolute rank differences and variance of the ranks (Huehn, 1990; Lu, 1995).
Mean AUDPCs for each clone at each location are given in Table 1. Mean AUDPC over locations ranged from a low of 377 in PA to a high of 917 in MN. The three late blight resistant checks (AWN86514-2, B0692-4, B0718-3) were highly resistant (Table 1 and Figure 1). Resistance levels in A97066-42LB, MSQ070-1 and W6360-1Rus were close to the resistant checks. Four clones were consistently among the most late blight susceptible over all locations: A0008-17E, BNC48-1, CO96141-4W, and Rio Colorado. The foliar reactions of all clones except MSL268-D were stable across locations.
Huehn, M. 1990. Euphytica 47:189-194.
Lu, H.Y. 1995. Agronomy J. 87:888-891.
Shaner, G. and R.E. Finney. 1977. Phytopathology 67:1051-1056.
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