Figure 1                                          Figure 2
    
Figure 3                                          Figure 4Introduction

Wheat streak mosaic virus (WSMV), Wheat mosaic virus (WMoV), and Triticum mosaic virus (TriMV) are important viral pathogens of wheat throughout the Great Plains region. (Fig. 1, 2, and 3) The most wide spread of these pathogens is WSMV, which is found throughout the Great Plains, with the highest occurrence found in Texas (Burrows 2008). Wheat streak mosaic virus, WMoV, and TriMV are all vectored by the wheat curl mite (Aceria tosichella Keifer), which are disseminated by winds from host to host spreading the pathogen. (Fig. 4) Losses due to wheat streak can be as high as 100% during times of severe infection. Little is also known about the spread of these pathogens and the effects of disease severity and yield losses from multiple and single infections. The Texas AgriLife research, Plant Pathology Department, has embarked on many efforts to help producers limit their risk of infection and better manage crop production once disease has occurred.

Overall goals of the Wheat streak mosaic virus research program at Texas A&M AgriLife, Amarillo

By studying the interaction between wheat viral diseases and their vector, we hope to better inform Texas producers of ways to not only limit infection, but to better manage production during times of high disease pressure and to limit losses due to these diseases. The overall project is divided into two areas dealing with epidemiology of the virus and vector as well as management strategies for determination of disease severity of multiple and single viral infections. There are six specific department research objectives listed below:

• Determine the effects of WSMV on root development and water use efficiency of infected wheat
  The Northern Texas Panhandle is a semiarid region and is highly dependent on irrigation for wheat production. Until recently it was unknown if wheat diseases such as WSMV had an empact on water use during times of infection. A study was conducted to determine the effects of WSMV on root development and water use efficiency of infected wheat. It was determined that WSMV infection reduced root weight by upwards of 50% or more during times of infection. The reduction of the root system reduced water uptake and water use efficiency wasting valuable water from irrigation (Price, accepted).
• Measure the effects of planting date on yield loss due to WSMV
  Wheat in northern Texas is commonly used as a dual purpose crop for both grazing and grain production. Wheat is planted early in the season in late August and early September causing the wheat to be exposed to a variety of insect pests as well as many viral diseases including WSMV. The severity of wheat streak is dependent on the time of infection. A study was conducted to determine the effects of time of inoculation on disease severity. It was concluded that earlier infections caused an increased reduction in grain yield when compared to later infection. (unpublished data).
• Create a statistical model to predict wheat streak severity along a diseases gradient in relation to yield and water use efficiency
  Wheat streak mosaic virus infection is often found to be highly severe at the point of entrance in a wheat field and then decrease in severity as it moves across the field. This movement creates a severity gradient from highly diseases to less severe diseases in specific areas of the field. A study was conducted to determine if model of the relationship between disease severity and yield could be created. Disease severity was determined using reflectance readings beginning at the highly diseased edge of a field along its diseases gradient to the less diseased area within the field. Disease readings were correlated with yield and water use efficiency data. The study determined that as disease severity decreased from the edge of the field, yield and water use efficiency increased and a time series model was described (Workneh, 2009).
• To create methods for detection of wheat curl mite populations within native grasslands and CRP pastures
  Wheat curl mite populations are known to survive on volunteer wheat and a variety of native field grasses and then spread to newly planted wheat in the fall and early spring. However, little is known about factors that affect their movement from grassland pastures including conservation reserve pastures to winter wheat fields.
• To determine differences in host/vector transmissibility of WSMV and TriMV
  It is routinely found that once infection occurs multiple viral pathogens can be found within one field however, the spread of each virus is not uniform suggesting a differences in transmissibility of these viruses by their vector.
• To compare diseases severity and yield losses due to single and multiple infections of WSMV and TriMV
  Wheat streak mosaic virus and triticum mosaic viruses.

Funding Sources

Cropping Systems Initiative, Texas Wheat Producers, and National Plant Diagnostics Network (Approximate total: $450,000, 2009–2011); Invited to submit full proposal to NHARP Program.

Dr. Charlie Rush – Professor of Plant Pathology
Dr. Fekede Workneh – Senior Researcg Scientist, Plant Pathology
Jacob Price – Senior Research Associate, Plant Pathology
Angela Simmons – Graduate Student