Assessments of potential management and environmental factors affecting regional occurrence of potato zebra chip disease
F. WORKNEH (1), D. C. Henne (2), J. A. Goolsby (3), J. M. Crosslin (4), S. D. Whipple (5), J. D. Bradshaw (5), A. Rashed (1), L. Paetzold (1), R. M. Harveson (5), C. M. Rush (1). (1) Texas A&M AgriLife Research, Bushland, TX, U.S.A.; (2) Texas A&M AgriLife Research, Weslaco, TX, U.S.A.; (3) USDA-ARS, Edinburg, TX, U.S.A.; (4) USDA-ARS, Prosser, WA, U.S.A.; (5) University of Nebraska, Panhandle Research and Extension Center, Scotts
Potato zebra chip (ZC), putatively caused by the bacterial pathogen ‘<i>Candidatus</i> Liberibacter solanacearum’, vectored by the potato psyllid (<i>Bactericera cockerelli</i>), is a newly emerging disease, which has caused widespread damage in much of the U.S. potato producing regions. Potato products from affected tubers show unacceptable dark coloration upon frying rendering them unmarketable. To characterize potential factors which influence regional variation in ZC occurrence, management and environmental variables were collected from six locations from south Texas to Nebraska over a three-year period (2010-2012). ZC occurrence was assessed in 26 fields in systematically selected plots (20 m ´ 30 m) in field edges and centers of the fields. The number of symptomatic plants/plot were classified into 2 categories (ZC £3 or ZC > 3) and subjected to discriminant function analysis to determine the association of the variables with the two ZC intensity categories. Latitudinal location, planting date, and maximum temperature were found to be the most important factors in distinguishing between the two categories. When individually subjected to logistic regression analysis, the three variables accounted for 90, 86, and 70% of the area under the curve, respectively. There was a significant but low negative correlation between ZC intensity and latitudinal location (<i>r</i>=-0.499; <i>P</i>=0.0094), indicating that the occurrence of ZC was greater in the southern- than in the northern regions.
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