Brown Spot Severity and Yield of Soybeans Regenerated from Calli Resistant to a Host-Specific Pathotoxin Produced by Septoria glycines. G. B. Lee, Former Graduate Student, Department of Crop Sciences, University of Illinois at Urbana-Champaign (UIUC). G. L. Hartman, USDA-ARS, Crop Protection Research Unit and Department of Crop Sciences, UIUC, Urbana, IL 61801; and S. M. Lim, Department of Plant Pathology, University of Arkansas, Fayetteville 72701. Plant Dis. 80:408. Accepted for publication 28 December 1995.. 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, 1996. DOI: 10.1094/PD-80-0408.

Regenerated soybean lines from the R₃, to R₇ generations were field-evaluated for their reactions to Septoria glycines, the brown spot pathogen, from 1991 to 1994. The regenerated lines from cvs. BSR201, Fayette, and L86P-16I5 were selected from calli resistant to a host-specific pathotoxin produced by S. glycines. Selected resistant plants to the pathogen from the R₃, generation produced R₄ progeny that were resistant, intermediate and susceptible in their reaction to S. glycines in 1991. In 1992, 1993, and 1994 among the R₃ to R₇ generations, brown spot reaction was only intermediate and susceptible. F₃ families obtained from a cross between R₃ regenerants and BSR201 had low heritability (23%) for resistance to S. glycines. Lines in the R₅ or R₆ generation, obtained originally from plants regenerated from calli of BSR201 that had intermediate and susceptible reactions to S. glycines in 1992, and five commercial soybean cultivars were evaluated for brown spot resistance, maturity, and yield in 1993 and 1994. Area-under the disease progress curve (AUDPC), maturity, and yield varied among entries. The 10 lines selected with an intermediate reaction had lower AUDPC, matured later, and had higher yields than the nine susceptible lines. Three regenerated lines, 2728, 2733, and 2734, had significantly (P = 0.05) lower AUDPC, later maturity, and higher yields than the other regenerated lines. AUDPC was significantly (P = 0.01) negatively correlated to yield (r = -0.29), to plant height (r = -0.74) and number of nodes (r = -0.39); but positively correlated to pods having 0 seed (r = 0.44) and two seeds (r = 0.49).