Graft, Pollen, and Seed Transmission of an Agent Associated with Top Spotting in Kalanchoë blossfeldiana. S. S. Hearon, Research Plant Pathologist, Florist and Nursery Crops Laboratory, USDA, ARS, Beltsville Agricultural Research Center-West, Beltsville, MD 20705. J. C. Locke, Research Plant Pathologist, Florist and Nursery Crops Laboratory, USDA, ARS, Beltsville Agricultural Research Center-West, Beltsville, MD 20705. Plant Dis. 68:347-350. Accepted for publication 19 December 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/PD-68-347.

Top spotting was shown to be caused by a graft-transmissible agent(s), which was also seedborne and transmitted through pollen from diseased plants. Seed transmission occurred in about 30–63% of the progeny if the pollen parent had top spotting. Bacilliform particles measuring 20–25 × 50–100 nm were observed in ultrathin sections of three of four diseased plants used as a source of scions in graft-transmission tests and in three of five diseased but none of five healthy progeny examined from seed-transmission tests.