Effects of Wheat Spindle Streak Mosaic Virus on Winter Wheat. Hung T. Nguyen, Graduate Assistant, Department of Agronomy, Pennsylvania State University, University Park 16802. Robert P. Pfeifer, Associate Professor of Plant Breeding, Department of Agronomy, Pennsylvania State University, University Park 16802. Plant Dis. 64:181-184. Accepted for publication 20 September 1979. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-181.

Infection by the wheat spindle streak mosaic virus (WSSMV) significantly reduced vigor of cultivars Abe and Redcoat in 1977-1978 in Pennsylvania. In both years, WSSMV infection occurred only on field plots that were inoculated with virus-bearing soil and planted by late September or early October. No leaf symptoms developed in the field, but plant growth and yield were significantly reduced at most locations on plots receiving infectious soil inoculum, compared with control plots receiving steam-treated soil inoculum. The 2-yr average reductions in grain yield, straw yield, and tillers were 7, 8, and 9%, respectively, on Hart and 24, 18, and 22% on Redcoat. Plant height reduction was significant on Abe and Redcoat but not significant on Hart, Blueboy, and Ruler. The percent of seed retained on a 2.8-mm slotted screen was significantly reduced on all cultivars except Hart. Based on field data and leaf symptom severity ratings, Hart was least affected, Blueboy and Ruler were moderately affected, and Abe and Redcoat were most affected by WSSMV. Steam-air soil treatment at 74 C for 30 min controlled the infectivity of the virus. Late planting in the fall of 1977 may have avoided WSSMV of wheat, but plant growth was severely reduced and grain losses were as high as 64%. Resistant or tolerant cultivars offer the best control.

Keyword(s): soil fumigation, soil steam-air treatment, soilborne virus, Triticum aestivum, wheat yield loss.