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Disease Note.

Velvetleaf as a Host for Septoria glycines. G. L. Hartman, USDA/ARS; Department of Plant Pathology, University of Illinois, Urbana-Champaign. G. B. Lee, Department of Plant Pathology, University of Illinois, Urbana-Champaign. Plant Dis. 79:426. Accepted for publication 10 March 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0426B.

Brown spot of soybean (Glycine max (L.) Merr), caused by Septoria glycines Hemmi and velvetleaf (Abutilon theophrastii Medik.) (1) occur in most soybean production areas. Soybean and velvetleaf leaves with lesions were collected at the Agronomy/Plant Pathology South Farm and disinfested with 0.5% NaOCl for 2 min, rinsed twice with tap water, and incubated on sterile moist filter paper in glass dishes for 4 days. Isolates were cultured on potato-dextrose agar at 23 C under continuous fluorescent light for 15 days. Colonies were black with globose or subglobose black pycnidia that produced hyaline, slightly curved, one- to five-septate conidia that were 9.837.8 μm x1.41.9 μm from velvetleaf and 1442 μm x1.42.1 μm from soybean. Cross inoculations using two soybean and one velvetleaf isolate on soybean cv. Williams and velvetleaf were conducted twice in the greenhouse. Leaf lesions and pycnidia developed on both plant species, but not on noninoculated control plants. Lesions on velvetleaf had irregular margins without surrounding chlorosis and were somewhat larger than the smooth-margin lesions surrounded by chlorosis found on soybean. Septoria glycines was reisolated from the infected leaves of both hosts, and was morphologically similar to the original isolates. Septoria glycines has been reported only on a limited number of legume species, but this report suggests that it may infect other hosts.

Reference: (I) L. W. Mitich. Weed Technol. 5:523, 1991.