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Disease Detection and Losses

Transmission and Distribution of Squash Mosaic Virus in Seeds of Cantaloupe. M. Alvarez , Former Ford Foundation Fellow, Department of Plant Pathology, University of California, Davis, CA 95616, Present address of senior author: Instituto de Investigaciones Agropecuarias, Est. Exp. La Platina, Casilla 5427, Santiago, Chile; R. N. Campbell, professor, Department of Plant Pathology, University of California, Davis, CA 95616. Phytopathology 68:257-263. Accepted for publication 1 September 1977. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-257.

Seed transmission of squash mosaic virus (SMV) in 62 seed lots from infected cantaloupe, cultivar PMR-45, averaged 10.6% and was not correlated with flowering or seed-production factors including time from virus inoculation to fruit set, fruit weight, or seed number and weight. Different methods of assaying for embryo infection of SMV indicated the same percentage infection. For example, when the naked embryos were split into distal and germinative ends, results of tests for SMV in the distal ends agreed with tests of the seedlings or plants grown from their respective germinative ends. Infected embryos always produced infected seedlings. In studies of the tissue relationships of SMV in seeds and seedlings local lesion assays on Cucumis metuliferus showed that there was a low level of infectivity in cantaloupe cotyledons during the first 2 days of germination but it increased after that. The roots and hypocotyls had less SMV than the cotyledons. The SMV was not detectable in cotyledons until the 3rd or 6th day of germination with the immunodiffusion and immunofluoresence tests, respectively. When detected, SMV was uniformly distributed in the cotyledons but immunofluoresence tests of protoplasts indicated only 18% infection. This virus also was found in seed coats as well as the papery layer consisting of remnants of the nucellus and endosperm. The SMV in the papery layer occurred independently of embryonic infection and its role in seed transmission is unknown. No SMV was detected in washed, triturated pollen of pumpkin cultivar, Small Sugar. Pollen transmission was not demonstrable in cantaloupe.