VIEW ARTICLE

Ecology and Epidemiology

Transmission of Xanthomonas phaseoli in Seed of Resistant and Susceptible Phaseolus Genotypes. C. R. Cafati, Former Rockefeller graduate fellow, Department of Botany and Plant Pathology, Michigan State University, East Lansing, 48824, Present address of senior author: INIA, Casilla 5427, Santiago, Chile, SA; A. W. Saettler, research plant pathologist, Edible Legumes, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Michigan State University, East Lansing, 48824. Phytopathology 70:638-640. Accepted for publication 13 December 1979. 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, 1980. DOI: 10.1094/Phyto-70-638.

A study was conducted on the possible transmission of the bean common blight pathogen Xanthomonas phaseoli (= X. campestris) (Xp) in seed of resistant Phaseolus acutifolius (tepary bean), and in P. vulgaris genotypes Great Northern (G.N.) Nebraska #1 selection 27, cultivar (G.N.) Valley, cultivar (G.N.) Jules, and breeding line MSU-51319 (all moderately resistant) and cultivars Tuscola and Seafarer (both susceptible). Field-grown plants were inoculated by scratching the dorsal suture of pods at the flat green stage of development with a syringe containing a suspension of R15-1 (an Xp mutant resistant to 50 ppm rifampin) at 10⁷ colony-forming units per milliliter. At normal maturity, only susceptible Tuscola had typical bacterial blight symptoms. Internally borne blight bacteria were isolated in both solid and liquid rifampin-containing media. Mutant R15-1 was recovered from 40, 42, 46, 51, 42, and 70% of seeds with any type of visible symptoms of internal blight infection in the genotypes tepary, Nebraska #1 selection 27, Valley, Jules, MSU-51319, and Tuscola, respectively. Mutant R15-1 also was recovered from 1.3, 2.0, 1.3, 1.9, 2.0, and 10.4% of symptomless seeds of the same genotypes, respectively. Our data suggest that tests to detect seedborne bacterial blight should be included in production programs for certified, blight-free seed of all dry bean cultivars.