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Pathogenic and Nutritional Variation in the Halo Blight Group of Fluorescent Pseudomonads of Bean. M. N. Schroth, Associate Professor, Department of Plant Pathology, University of California, Berkeley 94720; Vilma B. Vitanza(2), and D. C. Hildebrand(3). (2)(3)Laboratory Technician, and Associate Research Plant Pathologist, respectively, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 61:852-857. Accepted for publication 22 February 1971. DOI: 10.1094/Phyto-61-852.

There is no clear distinction in host ranges of Pseudomonas phaseolicola, P. glycinea, and P. mori, because some strains of each nomenspecies are capable of infecting certain cultivars of both the common bean and lima bean. Certain strains of P. phaseolicola also infected soybean. There was, however, a pronounced tendency for most strains to segregate along the commonly accepted host lines. Strains of P. phaseolicola attacked fewer soybean cultivars, and were less virulent than P. glycinea strains; the reciprocal also was true. The lima bean cultivars Fordhook 242, Fordhook Concentrate C-2, and King of the Garden were universally infected by all strains of the three nomenspecies. None of the tested P. phaseolicola and P. glycinea strains infected mulberry. Virulence among P. phaseolicola strains varied in two ways: (i) Certain strains were less virulent than others in all hosts tested; whereas (ii) virulence of some strains depended solely on the host. Neither race 1 nor race 2 strains of P. phaseolicola as defined by their reaction on Red Mexican UI-3 were homogeneous as to host range or virulence. Many so-called race 1 strains are merely low in virulence to all common bean cultivars, and did not infect the relatively more resistant ones. There was considerable variation in symptomatology on bean plants infected with P. phaseolicola. Some strains produced systemic symptoms on many hosts, others on a few hosts; whereas others produced only water-soaked lesions. The effects of infection by P. phaseolicola on plant growth depended upon bean cultivar, temperature, and bacterial strain. Nutritional studies of the nomenspecies indicated that strains with dissimilar host ranges differed in capacity to utilize substrates.