Growth and Flowering of Resistant Alfalfa Infected by Verticillium albo-atrum. B. W. Pennypacker, Doctoral Candidate, Department of Plant Pathology, The Pennsylvania State University. K. T. Leath, and R. R. Hill, Jr., Research Plant Pathologist, and Research Agronomist, USDA-ARS, U.S. Regional Pasture Research Laboratory, University Park, PA 16802. Plant Dis. 72:397-400. Accepted for publication 2 December 1987. 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, 1988. DOI: 10.1094/PD-72-0397.

Eight cultivars of alfalfa (Vertus, NAPB 110, NAPB 108, CW 8015, WL 316, Apollo II, Cimmaron, and Saranac AR) were evaluated following inoculation with Verticillium albo-atrum to determine whether the growth of plants lacking foliar symptoms was affected by the pathogen. All infected plants showed significant (P = 0.05) reductions in height, dry weight, and flowering. Plants free from foliar symptoms of Verticillium wilt also had significant (P = 0.05) reduction in height and flowering. Dry weight and height showed a significant inverse relation with the number of hours that the host/pathogen system experienced temperatures between 19 and 25 C, a temperature range favorable to growth of V. albo-atrum. Flowering was not significantly affected by pathogen-favorable temperatures. The effect of V. albo-atrum on flowering appears to be influenced by day length. No consistent differences were noted in cultivar response to V. albo-atrum.

Keyword(s): lucerne, Medicago sativa.