Barley field, St. Paul campus.

2014-15 Rapid Ag: Bacterial Leaf Streak of Wheat and Barley

December 8, 2014

Principal Leader

Ruth Dill-Macky

Department

Plant Pathology

Funding Awarded

  • 2014 Fiscal Year: $26,090
  • 2015 Fiscal Year: TBD

The Problem

BLS is an emerging disease problem in wheat and barley production in Minnesota. The disease has been significant in five of the past six cropping seasons with severities of up to 80% being reported in some fields and associated yield losses estimated at 13%.

Background

The reasons for the observed increase in BLS are not entirely clear, but the increased use of fungicides to control FHB and other fungal diseases of cereals likely led to an increased awareness of the problem as the observation of BLS symptoms is easier when other foliar pathogens are absent. BLS of wheat is caused by the bacterium Xanthomonas translucens with five pathovars (pv.) known to cause the disease over the host range of this taxon. X. translucens pv. undulosa is considered the primary pathovar adapted to wheat, while X. translucens pv. translucens is considered the primary pathovar adapted to barley. There is however evidence of some overlap in the host ranges of these pathovars.

In response to concerns over the upsurge of BLS, several cooperative projects were established in Minnesota and neighboring states. Several of the PI's in our research team have been active in research funded by the Minnesota-Small Grains Initiative (MN-SGI). The MN-SGI-funded research has been aimed at developing techniques for working with BLS of wheat and to examine the population structure of the pathogen. In addition, a regional project was established in 2010 with funding from the Minnesota Wheat Research and Promotion Council to supplement the research goals of the MN-SGI grant and to promote the regional effort on wheat BLS research.

The initial RARF proposal (FY12/FY13) aimed to broaden the scope of our research effort and allow us to move more rapidly toward our ultimate goal of deploying host resistance for the control of BLS, the most cost effective way to combat this disease. This project (FY14/FY15) aims to validate the data on varietal responses of wheat and barley to BLS that we have generated over the past two years. Confidence in our data is essential if we are to enable growers to make appropriate variety selections, both avoiding highly susceptible varieties and making the best choices for varieties to reduce their risk of BLS.

This project is also facilitating the ability of the wheat and barley breeding programs to more rapidly identify germplasm with resistance to BLS and develop breeding strategies using markers to accelerate breeding progress. With an increase in BLS, we are in need of methods to control the disease in wheat and barley production in Minnesota. There are no options for chemical control of BLS as fungicides are ineffective on bacterial pathogens. To date, no effective bactericide has been found for control of BLS nor has seed sanitation proven effective in eradicating the disease. In the past two years, we have learned much about the pathogen population, which appears to be quite genetically diverse. It is not yet known whether this diversity has implications for the deployment of resistance. We have gained valuable experience in establishing inoculated nurseries to screen for BLS, but have observed considerable variation in the spatial distribution of disease among plots within a trial, and within plots. To mitigate this variation we have adjusted our inoculation procedures but we need to validate the data from our initial studies to establish confidence in our observations. The knowledge we have gained over the past two years has however been invaluable in allowing us to begin the process of identifying and characterizing genetic resistance.

In the first RARF funded project, we gained information on the response of commercial varieties of wheat and barley to BLS and were able to provide that information to growers in the Variety Trials Results Bulletin allowing them to make informed decisions on variety selection to avoid the risk of BLS. Our data are, however, more variable than we would like and so validation of our results is needed.

The long-term benefits of our research will be to mitigate the economic losses to this disease, largely through improved genetic resistance in wheat and barley to BLS.

Objectives

  1. To validate information gathered in the FY12/FY13 biennium on the response of commercially available wheat and barley varieties to BLS.

  2. To validate the screens conducted on segregating populations for their response to BLS as the data obtained thus far are not of sufficient quality to complete association mapping.

  3. Identify potential sources of resistance to BLS by validating screening of core collections of barley germplasm. We have information that has enabled us to prioritize materials and thus we are able to focus these efforts, but need additional information on these materials to identify sources of resistance, particularly in barley.

  4. Amass sufficient data to reconcile discrepancies among screens to develop confidence in field and greenhouse screens. This objective moves us toward achieving reliable screens in the field and/or greenhouse so that the screening of materials can be conducted as a routine part of the wheat and barley breeding and pathology programs.

  5. Provide information to growers about the impact of BLS on wheat and barley production and control options. We will make the extension bulletin available to growers and provide additional information through extension activities including field days, grower meeting, print and electronic publications and through the media.