Greenhouse Technique to Evaluate Alfalfa Resistance to Phytophthora megasperma f. sp. medicaginis. B. A. Hohrein, Research Assistant, Department of Botany, University of Maryland, College Park 20742. G. A. Bean, Professor, Department of Botany, University of Maryland, College Park 20742, and J. H. Graham, Plant Pathologist, W-L Research, Inc., Highland, MD 20777. Plant Dis. 67:1332-1333. Accepted for publication 6 June 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1332.

A rapid, inexpensive, and reliable greenhouse technique was developed to evaluate large populations of alfalfa seedlings for resistance to Phytophthora megasperma f. sp. medicaginis. Seedlings were grown in a soil mix and inoculated when 12 days old. The percent stand 14 days later was used to rank entries. Rankings of entries for resistance to P. megasperma f. sp. medicaginis in the greenhouse were positively correlated with rankings in the Minnesota field test. Two populations of alfalfa derived as synthetic progenies from plants that survived the greenhouse test had higher percent stand compared with the original two parent populations when subjected to a second exposure to the fungus.