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Genetics

Effect of Host Genotype on Multiplication of Pseudomonas phaseolicola. Sara J. Stadt, Former graduate student, Department of Botany and Plant Pathology, Edible Legumes, Science and Education Administration, Agricultural Research, U.S. Department of Agriculture, Michigan State University, East Lansing 48824; A. W. Saettler, research plant pathologist, Edible Legumes, Science and Education Administration, Agricultural Research, U.S. Department of Agriculture, Michigan State University, East Lansing 48824. Phytopathology 71:1307-1310. Accepted for publication 16 April 1981. 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, 1981. DOI: 10.1094/Phyto-71-1307.

We studied the multiplication of Pseudomonas phaseolicola (Pp) in seedlings of halo blight susceptible Charlevoix and tolerant Montcalm and Seafarer bean cultivars. Strain R13 of Pp, which is resistant to rifampin, was used to facilitate isolation of the bacteria from field material. Dilutions of ground (total) and rinsed (surface) first, third, or fifth trifoliolate leaves were plated on King’s Medium B containing 50 μg/ml each of rifampin and cycloheximide. Increase of Pp R13 in leaves of cultivar Charlevoix followed a typical bacterial growth curve. Populations of Pp in the stationary phase remained high for up to 15 days on all leaves of Charlevoix; on third trifoliolate leaves, 27% of the total population was surfaceborne. Lower numbers of Pp R13 were detected in leaves of cultivar Montcalm and 5% was surfaceborne. Seafarer supported slightly higher numbers of Pp R13 than Montcalm, and 8% of the total was surfaceborne. Tolerant bean cultivars may serve as carriers of Pp, and secondary spread from them may occur before visible symptoms develop.