|Samac, Deborah - Debby|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2007
Publication Date: 4/1/2008
Citation: Hollingsworth, C.R., Samac, D.A., Atkinson, L.M., Larsen, J.E., Motteberg, C.D., Abrahamson, M., Glogoza, P., MacRae, I.V. 2008. Region and field level distributions of aster yellows phytoplasma in small grains crops. Plant Disease. 92(4):623-630. Interpretive Summary: Small grains crops such as wheat, barley, and oat show similar symptoms when afflicted with barley yellow dwarf disease or aster yellows disease. It is likely that the two diseases are often mis-diagnosed in the field. A 3-year survey was conducted using plants collected from Minnesota and North Dakota small grain fields to determine the prevalence of both diseases using laboratory assays. Although the number of fields with each disease varied depending on the year, aster yellows disease was far more common than barley yellow dwarf disease. Aster yellows disease was found in wheat, oat, and barley plants. The disease was detected early in the growing season and persisted in mature plants. Both diseases were widespread in the survey area in all 3 years. A quantitative assay was developed to determine the population density of the aster yellows pathogen within wheat plants. The assay was used to survey for the pathogen within wheat fields. The pathogen was more prevalent in plants at the edges of fields compared to plants in the center of the field. This suggests that the insect vector for the disease moves into the field from perimeter areas. This research showed that aster yellows disease is common on small grains crops but has been largely unrecognized in the past. Correct diagnosis is needed for applying appropriate control measures to reduce damage from these diseases that reduce crop yield and grain quality.
Technical Abstract: Aster yellows (AY), a disease of small grain crops caused by aster yellows phytoplasma (AYp), produces disease symptoms similar to barley yellow dwarf (BYD). From 2003 to 2005, small grain production fields in Minnesota and North Dakota were surveyed to determine the incidences of AY and BYD. In-field spatial patterns of AY infected plants were also investigated. Plants collected along a five point transect line were tested for AYp using nested PCR and quantitative real time PCR assays, and extracted plant sap was tested for serotypes PAV and RPV of Barley yellow dwarf virus(BYDV) using ELISAs. During 2003, 2004, and 2005 AYp was detected in plants from 49%, 15%, and 7%of tested fields, respectively, while BYDV was found in plants from 2%, 0%, and 5% of fields, respectively. Average amplicon count number indicated an in-field spatial trend for greater incidence of AYp and increased populations of AYp in plants located near field edges with comparably low copy numbers at transect point locations toward the direction of field center. In some years, AY is a common but largely undetected disease issue on small grain crops in the U.S. Northern Plain States.