Application of Cross-Protection to the Control of Black Soybean Mosaic Disease. Y. KOSAKA, Plant Pathologists, Kyoto Agricultural Research Institute, Kameoka, Kyoto 621 Japan. T. FUKUNISHI, Plant Pathologists, Kyoto Agricultural Research Institute, Kameoka, Kyoto 621 Japan. Plant Dis. 78:339-341. Accepted for publication 9 December 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0339.

In 1990 and 1991, approximately 20,000 and 78,000 seedlings, respectively, of black soybean (Glycine max (L.) Merr. cv. Shin Tambaguro) were transplanted 1-3 days after protective inoculation with an attenuated isolate of soybean mosaic virus (SMV), Aal5-M2, in seed farms in Kyoto Prefecture, Japan. In the plants that received the protective inoculation, virulent strains of SMV were effectively suppressed. Seeds virtually free of SMV were produced in 1990 (971 kg/ha), and free of SMV in 1991 (4,740 kg/3.9 ha). Black soybean seedlings grown from these seeds were widely transplanted in growers' fields in 1991 (45 ha) and 1992 (50 ha) in Wachi, Kyoto. The incidence of virulent strains of SMV in late July (preflowering stage, about 40 days after transplanting) was found to be 1.3% in 1991 and 0.8% in 1992, in contrast to the rates of over 60% in 1989 and 1990. The use of seeds from Aal5-M2 inoculated plants was also found to be effective for the control of SMV in other areas during 1992.