Levels and identities of nonrhizobial microorganisms found in commercial legume inoculant made with nonsterile neat carrier

Sixty samples of commercial North American legume inoculants manufactured for sale in 1994 using nonsterile pear as carrier were tested for Rhizobium (or Bradyrhizobium) content and nonRhizobium biological contaminant load. products of three major producers of such inoculants for sale in Canada were examined. Viable Rhizobium content varied from 5.6 x 10(5) to 8.1 x 10(9) cells/g. while the contaminant load varied from 1.8 x 10(8) to 5.5 x 10(10) cfu/g. Most of the inoculants contained more nonrhizobial organisms than they did rhizobia. Identifications wen made of the most numerous nonrhizobial bacteria occurring in 100 samples of inoculants collected in 1993 and 1991. The most commonly identified contaminant was Xanthomonas maltophilia. Pseudomonas aeruginosa. Klebsiella pneumoniae. and Enterobacter cloacae were also found at high levels in some products. Contaminant organisms capable of inhibiting rhizobial growth in plate culture were found in the products of all three manufacturers.