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Disease Detection and Losses

Reduction in Plant Development, Yield, and Grain Quality Associated with Wheat Spindle Streak Mosaic Virus. Barry M. Cunfer, Department of Plant Pathology, Georgia Station, University of Georgia, Griffin 30223; James W. Demski, and David C. Bays. Department of Plant Pathology, Georgia Station, University of Georgia, Griffin 30223. Phytopathology 78:198-204. Accepted for publication 10 August 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-198.

Wheat spindle streak mosaic virus (WSSMV) caused severe reductions in yield and grain quality of wheat cultivars Florida 301, Florida 302, and Coker 797. Coker 797 is the most susceptible cultivar, on the basis of the various yield and quality criteria. The resistant cultivars Stacy and Coker 916 sustained no significant reduction in any component of yield or grain quality from infection by WSSMV. Most damage began during the winter, 30–60 days after planting, when a rapid increase in WSSMV concentration, documented by enzyme-linked immunosorbent assay (ELISA), was associated with significant reduction in tillering and plant biomass of susceptible cultivars. During one season, record low temperatures in late January further contributed to yield reduction, due to the death of WSSMV-weakened plants. Anthesis was delayed 7–10 days in WSSMV-infected plants, and maturity was delayed 5–7 days. Reduced growth and development of surviving tillers of susceptible cultivars resulted in significant reduction in biomass, 1,000-kernel weight, and test weight. The milling and baking qualities of grain from plants affected with wheat spindle streak mosaic were reduced to unacceptable levels during one season, when 1,000-kernel weight and test weight were severely reduced. Milling and baking qualities were affected less during a second season. A delay in planting beyond recommended dates did not reduce disease incidence or severity, because soil temperatures and moisture conditions were favorable for infection throughout the winter. Resistant cultivars harbor WSSMV in roots, as documented by ELISA. The ELISA data indicate that resistance is related to reduced virus concentration in resistant cultivars. Polymyxa graminis cysts were also observed in roots of all cultivars.