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The Effect of Various Peptone Sources on Germ Tube Elongation in Uromyces phaseoli. R. M. Niles, Graduate Research Assistant, Department of Botany, University of New Hampshire, Durham 03824; Avery E. Rich, Plant Pathologist, Department of Botany, University of New Hampshire, Durham 03824. Phytopathology 61:562-564. Accepted for publication 15 December 1970. DOI: 10.1094/Phyto-61-562.

The effect of different peptones on germ tube elongation in Uromyces phaseoli was studied. Six commercial peptones and plant extracts of pinto bean and lima bean were compared by adding them individually to a basal medium of Czapek’s minerals and 2% agar, adjusted to pH 6.8. Uncontaminated bean rust uredospores were seeded onto the appropriate media and incubated at 17 C. The effect of increasing the concentration of peptone and yeast extract was studied. Lima bean extract was the most successful stimulator of germ tube elongation. Among the commercial peptones, only Difco peptone failed to yield tube lengths at least twice those recorded for the control. Increasing concentrations of Evans’ peptone, lima bean extract, and yeast extract resulted in longer germ tubes up to a maximal point, after which higher concentrations yielded shorter germ tubes. A synergistic effect was noted in all cases when yeast extract was combined with peptones or plant extracts.

Additional keywords: bean rust, spore germination.