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Title: Evidence that the Zebra Chip Disease and the Putative Causal Agent Can be Maintained in Potatoes by Grafting and In Vitro

Author
item Crosslin, James
item Munyaneza, Joseph - Joe

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2008
Publication Date: 5/15/2009
Citation: Crosslin, J., Munyaneza, J.E. 2009. Evidence that the Zebra Chip Disease and the Putative Causal Agent Can be Maintained in Potatoes by Grafting and In Vitro. American Journal of Potato Research. 86:183-187.

Interpretive Summary: A recently-decribed potato disease, zebra chip, is causing economic damage in several parts of the United States and also in Mexico. The disease causes discoloration of the potato tubers and these subsequently turn very dark when the chips are fried and are commercially unacceptable. The disease has been associated with an insect, the potato psyllid, but the exact cause of the problem is not fully understood. We have been maintaining the disease by grafting diseased shoots onto healthy potato plants. The disease has been maintained for more than a year by this method and we are continuing studies on the exact cause of zebra chip. Additionally, we have detected a potential bacterial pathogen in the diseased plants and tubers.

Technical Abstract: In the last several years, a disorder of chipping potatoes that causes internal browning of raw tubers and very dark chip color when the tubers are fried has been described from the southwestern United States. The discoloration often shows as rays or stripes and the common name “zebra chip (ZC)” has been used to describe the disorder. The disease has been conclusively associated with the potato psyllid, Bactericera cockerelli, but a suspected pathogen that may be associated with the ZC disorder has only very recently been described. In our efforts to identify the causal agent we have been maintaining the disease by tip grafting into several commercially important cultivars of potatoes, including Atlantic, Russet Burbank, and Russet Norkotah. Herein we report the results of these grafting experiments and describe the symptoms produced in grafted plants and daughter tubers. Many of the grafted plants produced tubers with symptoms typical of the disease. In Atlantic, 104 of 138 grafted plants developed foliar symptoms of ZC and 72 plants produced ZC-symptomatic daughter tubers. We have also maintained the disease in in vitro produced plants. In addition, the putative ZC pathogen has been detected in infected plants and tubers by PCR.