Distribution of a Take-All Suppressive Strain of Pseudomonas fluorescens on Seminal Roots of Winter Wheat.
An antibiotic-resistant strain of Pseudomonas fluorescens, that suppresses take-all of wheat, was used to study the distribution of the bacteria on seminal roots of wheat after being introduced onto seeds. Cells of P. fluorescens were isolated from the entire length of the root, and density of the introduced bacteria declined with the distance from the base of the root. Maximum populations of 10 to 10 CFU and 10 to 10 CFU per cm of root were detected on sections of roots near the seed and root tip, respectively. The introduced bacteria competed well with indigenous bacteria, comprising at least 25% of the fluorescent pseudomonads detected by plate counts for 48 days after planting.
Weller
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Root Disease and Biological Control Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Pullman, Washington 99164.