Phomopsis Seed Decay in Soybean Isolines Differing in Stem Termination, Time of Flowering, and Maturity
- P. R. Thomison ,
- W. J. Kenworthy and
- M. S. McIntosh
Infection of soybean [Glycine max (L.) Merr.] seed by Phomopsis longicolla Hobbs is a major cause of poor seed quality in regions where the climate is warm and humid during and after seed maturation. The objective of this study was to evaluate effects of stem termination, time of flowering, maturity, and various combinations of these characteristics on seed germination and infection of seed by P. longicolla. The cultivar Clark and seven of its near-isogenic lines differing in stem termination (indeterminate vs. determinate vs. semideterminate), time of flowering (normal vs. delayed vs. late), and maturity (normal vs. late) were evaluated for seed-borne disease in Maryland at two locations in 1984 and 1985 and one location in 1986. Seed infection by P. longicolla was increased 20% and seed germination reduced 16% in determinate isolines compared to indeterminate isolines. Semideterminate isolines exhibited levels of fungal seed infection and seed germination intermediate to those of the indeterminate and determinate isolines. Late flowering and late maturity decreased seed infection by P. longicolla 48% and improved seed germination 97%. Effects of delayed flowering on seed infection and seed germination were not consistent. Growing early maturing, determinate cultivars in the mid-Atlantic region may increase the potential for seed disease problems due to P. longicolla, if weather conditions are conducive for disease development.
Copyright © 1990.