CULTIVAR-SPECIFIC GROWTH PROMOTION OF SPRING WHEAT (TRITICUM-AESTIVUM 6) BY COEXISTENT BACILLUS SPECIES

Seven bacterial strains belonging to the genus Bacillus were isolated from rhizosphere soil of spring wheat (Triticum aestivum L.) cv. Katepwa. The plants from which the microorganisms were isolated were collected from a field that had been continuously cropped with spring wheat for the past 27 years. Cultivar Katepwa had been grown for the last 5 years whereas the closely related cv. Neepawa had been cultivated for the 12 previous years. When tested as single strain inoculum in a sterilized sand and Turface (montmorillonite clay) mix, six of seven isolates promoted root growth of cv. Katepwa spring wheat (p < 0.05), but none promoted that of cv. Neepawa or of the more distant genetic relative cv. HY320. Shoot height was also increased in cv. Katepwa (p < 0.1), but shoot weight of all three cultivars was unaffected by inoculation. Consequently, the root to shoot weight ratio of cv. Katepwa was also greater because of bacterization. These results indicate that beneficial bacteria may be isolated by employing a natural plant cultivar enrichment technique.