1a. Objectives (from AD-416):
Design a ZC specific realtime PCR diagnosis for reliable detections of ZC-infected potato and potato psyllid. 2. Design and develop multi-locus DNA Simple Sequence Repeat (SSR) DNA markers to genotype and assess genetic diversity of ZC-associated Liberibacter bacteria.
1b. Approach (from AD-416):
1. Clone and sequence ZC Liberibacter pathogen to identify suitable sequencing regions for designing realtime PCR. Validate sensitivity and specificity of detection. 2. Conduct whole genome analyze of ZC Liberibacter draft genome and identify SSR loci for designing SSR primers. 3. Conduct population genetic analysis of ZC-associated Candidatus Liberibacter and assess genetic diversity of the pathogen.
3. Progress Report:
This research is in support of objective 2 (the goal of which is to elucidate molecular interactions of plant hosts and bacterial pathogens) of the in-house project. ‘Candidatus Liberibacter solanacearum (Lso)’ is associated with Zebra Chip (ZC) disorder in potatoes. With the availability of Lso genome sequences, genome-wide sequence analyses were conducted to design and develop “simple sequence repeat” (SSR) and “multilocus sequence typing” (MLST) molecular markers for Lso. Both marker systems proved useful for detection and typing of Lso isolates. While the putative causal agent of ZC has been identified, information regarding ‘Ca. L. solanacearum’ genetic diversity, structure and adaptation, as well as epidemiological relationships across different geographical regions and hosts is limited. The MLST markers developed in this study effectively typed and estimated genetic diversity of Lso isolates. Using these marker systems, two major lineages were identified among Lso strains in North America (USA and Mexico) and New Zealand. While epidemiological significance of the two lineages is not clear, genetic information obtained from both marker typing systems yielded insight into genetic diversity, evolution, and adaptation of this pathogen. The combination of epidemiological data and genetic information will advance knowledge in understanding sources and dynamics of ZC disease and facilitates development of effective disease management of potato zebra chip.