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United States Department of Agriculture

Agricultural Research Service


Location: Vegetable Crops Research

2010 Annual Report

1a. Objectives (from AD-416)
Workshops will be held at regional and national Allium meetings. We will develop a mechanical transmission protocol or Iris Yellow Spot Virus and validate sources of resistance or tolerance identified in field evaluations.

1b. Approach (from AD-416)
Sources of IYSV resistance or tolerance will be validated in controlled environments by mechanical inoculations. Deliver validated germplasms to private and public sector breeder. Develop workshops for public and private-sector researchers, students, and regional grower and consumer groups for onion to illustrate the usefulness of genomics to solve high-priority research goals.

3. Progress Report
A set of indicator hosts that respond by producing a specific host reaction following mechanical inoculation with Iris Yellow Spot Virus (IYSV) were identified. These host species produce either localized infection (the virus is able to infect/replicate and produce symptoms in the inoculated leaves but fails to move to younger, uninoculated leaves. Using this set of IYSV-susceptible, differential indicator hosts, several field-collected IYSV isolates were screened to identify biologically distinct strains that differ in their disease severity. Preliminary data suggests that there are strains that differ in their ability to colonize and cause systemic infection in infected plants. Efforts to develop an efficient mechanical inoculation method to infect onion with IYSV are ongoing. We were able to reproduce IYSV symptoms in mechanically inoculated onion plants. Use of IYSV-infected N. benthamiana plants appear to be a better source of inoculum to establish IYSV in onion. We cloned and sequenced the complete ribonucleic acids (L RNA) that codes for the RNA-dependent RNA polymerase. Availability of the sequence information of all three RNAs of IYSV would facilitate design and use of individual RNA-specific primers to track the movement of the virus in onions following mechanical inoculation.

4. Accomplishments

Last Modified: 10/18/2017
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