CROP SPECIFICITY OF RHIZOSPHERE PSEUDOMONADS AND THE INVOLVEMENT OF ROOT AGGLUTININS

Crop specificity of rhizosphere-inhabiting fluorescent Pseudomonas spp was studied for potato, grass and wheat grown in a silty loam soil. For each crop about 50 dominant Pseudomonas isolates were obtained from the rhizosphere. Isolates were distinguished by comparing their lipopolysaccharide (LPS) and cell envelope protein (CEP) patterns About 30 distinct patterns were detected for each crop. The majority of LPS and CEP patterns observed for each crop was not detected on the other crops, suggesting a crop specificity for certain Pseudomonas populations. From each crop distinct Pseudomonas isolates were used to study crop-specific root colonization by growing potato, grass and wheat plants in soil bacterized with a mixture of these isolates of the three crops. Crop specificity in root colonization could not be demonstrated. The involvement of root agglutinins in the composition of rhizosphere Pseudomonas populations was examined. Reactions of distinct Pseudomonas isolates from each crop with crude or partially-purified agglutinin preparations of potato, grass or wheat did not correlate. We concluded that the composition of rhizosphere Pseudomonas populations differed between crops. However, crop-specific root colonization or crop-specific agglutination could not be demonstrated with the experimental approach used.