2012 Annual Report
1a.Objectives (from AD-416):
1. Observe development of zebra chip in potato tubers from plants infected late season (< 2 wks. before harvest).
2. Determine how titers of CLso in infected tubers change over time in storage.
3. Relate changes in phenolic, amino acid, and carbohydrate compound levels to zebra chip symptoms and CLso titers.
1b.Approach (from AD-416):
Collaborators from Texas AgriLife Research (Texas A&M University) will inoculate two different cultivars of potato and place into storage. After 0.5, 1, 2, and 3 months of storage, they will evaluate symptom development and harvest tubers to be used for chemical analyses. High performance liquid chromatography will be used on collected potato tuber samples to assess phenolic and carbohydrate levels, and gas chromatography will be used to assess amino acid levels. Quantitative PCR will be used to assess CLso titers. Univariate ANOVAs will determine which compounds are significantly increased in infected tubers compared to equivalent non-infected controls. Pearson’s or Spearman’s correlations, as appropriate, will find associations between chemistry, symptoms, CLso titers, and time in storage.
Results from this study are in support of Objective 4 of the parent project. Three different cultivars of potatoes (one Atlantic, one Russet, and one red potato variety) were inoculated with ‘Candidatus Liberibacter solanacearum’ (CLso), the putative causal agent of zebra chip disease, by allowing CLso-positive potato psyllids to feed on plants kept in cages at the Texas AgriLife Research Center. CLso inoculations occurred one, three, five, seven, or nine weeks prior to harvest, and additional potatoes were left non-inoculated as controls. Disease symptoms were assessed for all harvested potatoes. Slices of potato tubers were shipped to USDA-ARS in Parlier, California, for initial evaluation of amino acid, carbohydrate, and phenolic concentrations. Additional samples from tubers placed in cold storage are due to be delivered to USDA-ARS every two weeks through October 2012 for analysis of amino acid, carbohydrate, and phenolic content. This will provide understanding of how CLso infected tubers in cold storage undergo phytochemical changes over time.