DYNAMICS OF WHEAT SPINDLE STREAK MOSAIC BYMOVIRUS IN WINTER WHEAT

Authors: CARROLL, J - CORNELL UNIVERSITY; BERGSTROM, G - CORNELL UNIVERSITY; Gray, Stewart

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Wheat spindle streak mosaic virus causes a disease of wheat throughout much of the world & is especially serious in the Northeastern United States where it can cause yield losses exceeding 20%. The virus is known to be transmitted by a fungus, but how and when the virus is spread has not been studied in depth due to the difficulty of working with fungal transmitted viruses and unreliable assays to diagnosis the virus diesease. Recently we developed antibodies specific to this virus and perfected an assay that allowed for reliable detection of the virus in field grown plants. In this study we monitored the movement of the virus within plantings of two cultivars of winter wheat to determine when infection takes place and what influence soil temperature has on the infection process. Our results indicated that a majority of the plants are infected in the fall shortly after planting, although infection cycles can occur throughout the fall and dinto the spring. The virus can be detected in plants throughout the growin season using our assay, but visual symptoms are only seen for a brief period in the spring. The infection process is influenced most significantly by soil temperature with temperatures between 5 and 15C being optimal. An understanding of when infection occurs and the dependence of the infection process on soil temperature will aid in the development of disease control strategies.

Technical Abstract: The dynamics of wheat spindle streak mosaic bymovirus in winter wheat were studied during two crop cycles in a field site with a history of high virus incidence. Individual plants of two susceptible cultivars were sampled from autumn to spring and the presence of virus antigen in roots and leaves was determined by ELISA. Virus incidence was higher in cv. Frankenmuth than in cv. Augusta. During year one, incidence of viral antigen in roots remained very low for four months after sowing, and did not reach maximum levels until the following spring. During year two, incidence of viral antigen in roots rose to maximum levels in autumn, only three months after sowing. These results strongly suggested that root infection occurred in spring as well as in autumn. In both cultivars and in both years, we detected the virus in roots one month prior to its detection in leaves, suggesting that virus moves slowly from roots into leaves. Maximum incidence of virus in leaves occurred in spring of both years, coinciding with the period of symptom development. Typical symptoms (yellow streaks, spindles, and mosaic) were observed in year two, whereas only mild mosaic was observed in year one. Virus antigen was detected in nonsymptomatic leaves from two months after sowing through crop senescence. Because antigen could be detected in roots throughout the crop cycle, and zoosporangia and cystosori of the fungal vector could be detected one and two months, respectively, after sowing, it is possible that wheat spindle streak mosaic bymovirus is acquired and/or spread by the vector during the majority of the crop cycle.