2012 Annual Report
1a.Objectives (from AD-416):
Develop improved detection and diagnostic methods for the newly described zebra chip disease of potatoes and the putative pathogen, a new species of Candidatus Liberibacter. Evaluate diverse potato germplasm for resistance to development of tuber symptoms of the disease.
1b.Approach (from AD-416):
Analyize currently available DNA sequence information and develop effective molecular tools for detection of the pathogen. Continue obtaining sequence information on the pathogen by cloning additional portions of the genome. Inoculate diverse potato germplasm with zebra chip via grafing or psyllid feeding and rate tubers for disease. Test weeds and alternate hosts for the putative pathogen.
Final Report for 5354-21220-010-51R - Potato zebra chip disease (ZC) is an emerging and economically important disease in Mexico, Central America, parts of the US, and New Zealand. Disease losses have been in the millions of dollars in the US in the last 7 to 8 years. ZC is caused by infections with a bacterium, Candidatus Liberibacter solanacearum (Lso). This bacterium is transmitted to potatoes by the potato psyllid, an insect similar to aphids. For the last four years we have been testing psyllids for Lso that were collected in the central US (TX, KS, NE, CO, etc.) by ARS researchers and university cooperators in Texas. The purpose is to determine if the incidence of Lso in a psyllid population could be used as a predictor of ZC disease development in a potato crop. This year we have tested more than 4,600 psyllids and the Lso infection rate is less than one percent. Fields near the insect collection site are being monitored for the incidence of ZC and this will be compared with the Lso infection rate to determine the possible association. In the first three years’ testing, there was a statistically significant relationship between psyllid infection rates and the incidence of ZC in several fields in TX. The ability to “predict” the risk of developing ZC by testing of psyllids near potato fields provides growers valuable information regarding the application of pest control measures to reduce the psyllid populations. This, in turn, would reduce the economic impact of ZC in their crops.
This project studies the population dynamics of the potato psyllid and infection rates of psyllids with the Lso bacterium which contributes to Objective 2 of the in-house project, "Determine host resistance options, epidemiological parameters and develop diagnostic tests for emerging pests and pathogens of potato".