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, The Pennsylvania State Univ., University Park, PA 16802
In 2006, 24 potato clones (5 varieties, 11 selections, 8 LB differentials) were evaluated in the field for foliar late blight at five U.S. locations: Presque Isle, ME; Rosemount, MN; Prosper, ND; Corvallis, OR; and, Rock Springs, PA. Plots were planted in a randomized complete block design with 3-4 replications per location. Due to limited seed, 97A-51, B0767-2, and Rio Grande were not evaluated at all locations. For this reason, the box and whisker plot does not include these three clones.
All locations except Presque Isle, ME inoculated the plots with US-8 isolates of Phytophthora infestans. Naturally occurring US-8 isolates were identified in ME. Irrigation was applied as needed in all locations except ME 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 24 (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).
In OR ten tubers per clone were harvested from each of four replicated plots, stored for two weeks, and then rated for percent tuber blight.
Mean AUDPCs for each clone at each location are given in Table 1. Mean AUDPC over locations ranged from a low of 281in ME to a high of 533 in MN. The three late blight resistant checks (AWN86514-2, B0692-4, B0718-3) and two of the late blight differentials (LBR8, LBR9) were highly resistant (Table 1 and Figure 1). Rankings of the foliar reactions of all clones were stable across locations. Tuber blight exceeded 40% in A91790-13 (45%), A93157-6LS (48%), and Castile (73%).Box and whisker plot AUDPC - PDF
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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