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Selection and Regeneration of Soybeans Resistant to the Pathotoxic Culture Filtrates of Septoria glycines. H. S. Song, former graduate research assistant, Department of Plant Pathology, University of Illinois, Urbana 61801; S. M. Lim(2), and J. M. Widholm(3). (2)plant pathologist and professor, Crop Protection Unit, Agricultural Research Service, U.S. Department of Agriculture, and Department of Plant Pathology; University of Illinois, Urbana 61801, Current address: Department of Plant Pathology, University of Arkansas, Fayetteville 72701; (3)professor, Department of Agronomy, University of Illinois, Urbana 61801. Phytopathology 84:948-951. Accepted for publication 7 June 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-948.

Soybean plants resistant to a host-specific pathotoxic culture filtrate of Septoria glycines were regenerated by organogenesis from immature embryos of the cultivar BSR 201 and from mature seeds of three genotypes, BSR 201, Fayette, and L1615. When the progeny obtained from immature embryos were evaluated for brown spot disease resistance in the field, the R2 (the second selfed generation of regenerated plants) and R3 resistant plants did not develop disease symptoms until the R6 growth stage. The incubation period of S. glycines in the resistant plants was at least 5 wk longer than the incubation period in susceptible plants. The resistant plants differed from their parental plants in height, maturity, growth habit, and fertility. Resistance to S. glycines culture filtrate continued to segregate in unexpected ways after several generations of selfing. Among the resistant plants obtained from mature seeds, only progeny from BSR 201 inherited disease resistance, and these plants were of normal height. The resistant plants obtained from immature embryos and mature seeds matured later than the parent. This study showed that soybean plants with resistance to S. glycines can be selected from cultured cells of brown spot-susceptible cultivars using pathotoxic culture filtrates of S. glycines.