VIEW ARTICLE

Isolation, Pathogenicity and Characterization of Fluorescent Pseudomonads Associated with Discolored Alfalfa Roots. P. A. Shinde, Graduate Student, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; F. L. Lukezic, Associate Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 64:865-871. Accepted for publication 23 January 1974. DOI: 10.1094/Phyto-64-865.

Isolations made from discolored roots of stunted alfalfa plants of cultivars resistant to bacterial wilt caused by Corynebacterium insidiosum consistently yielded fluorescent pseudomonads and Erwinias. In greenhouse tests, alfalfa seedlings inoculated with the pseudomonads sometimes developed yellow leaves which later wilted or the entire plant suddenly collapsed and died. The pseudomonads were nonspore-forming, gram negative, capsulated, rods with three to six polar flagella. All six isolates of pseudomonads reacted similarly to most of the physiological and biochemical tests to which they were subjected. The oxidase-positive, alfalfa pseudomonads differed significantly from Pseudomonas chichorii in seven of twelve physiological tests. They differ from P. marginalis only in their ability to cause hypersensitivity in tobacco, and in their inability to produce arginine dihydrolase. We think that the fluorescent pseudomonads from alfalfa roots are a variety of P. marginalis and propose the name P. marginalis var. alfalfae.