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Analysis of the Accumulation of Pea enation mosaic virus Genomes in Seed Tissues and Lack of Evidence for Seed Transmission in Pea (Pisum sativum)

First and third authors: New Zealand Institute for Plant & Food Research Ltd., P.O. Box 4704, Christchurch 8140, New Zealand; second author: United States Department of Agriculture--Agricultural Research Service (USDA-ARS), The Vegetable and Forage Crop Research Unit, 24106 N. Bunn Rd., Prosser, WA 99350; fourth author: North Dakota State University, Department of Plant Sciences, P.O. Box 6050, Fargo 58108-6050; and fifth author: USDA-ARS Western Regional Plant Introduction Station, 59 Johnson Hall, WSU, Pullman, WA 99164-6402.

Pea enation mosaic virus (PEMV) is an important virus disease of pea. International movement of commercial pea cultivars and germplasm can be problematic due to uncertainty about seed transmission of the viruses responsible for the disease. Whether PEMV is seedborne was assessed by collecting developing seed from infected plants and determining the relative concentrations of the PEMV-1 and PEMV-2 viral genomes using quantitative real-time reverse-transcription polymerase chain reaction. The relative accumulation of PEMV-1 and PEMV-2 was ≈1,240 and 13,000 times higher, respectively, in leaf than in embryo tissues. Accumulation of PEMV-1 and PEMV-2 RNA was also significantly higher in pod walls and seed coats than in cotyledons or embryo axes. No evidence was obtained for seed transmission of PEMV in pea. Although PEMV-1 and PEMV-2 genomic RNAs were found in developing seed, no PEMV symptoms were observed in the field on more than 50,000 plants from seed derived from PEMV-infected source plants. These data demonstrate that PEMV is seedborne in pea but do not support a previous report that PEMV is seed transmitted. Absence of seed transmission may result from the low abundance of PEMV viral genomes in embryo tissue.