ISOLATION AND PLANT GROWTH-PROMOTING CHARACTERIZATION OF POTASSIUM SOLUBILIZING BACTERIA IN RHIZOSPHERE OF SOME CROPS IN VIETNAM

Many soil microorganisms are able to dissolvethese types of potassium and have been applied in agriculture. These potassium solubilizing bacteria (KSB) have also been shown to have by many other direct or indirect plant growth-promoting activities. This study's aim was isolation, screening and plant growth-promoting characterization of KSB from rhizospheric soil of some crops in Vietnam. The results were that thirty-four KSB isolates were collected on Aleksandrov agar medium from ten soil samples from the rhizospheres of banana, pitaya, and mango. By the spot streak technique on this medium, three KSB isolates including BE204, BE208 and BE220 were screened with the potassium solubility indexes 10.87, 10.97, and 10.72, respectively. All of three selected isolates were identified as belong to Burkholderia genus by the specific protein springers, in which, BE208 had the best match with B. gladiola. The two strains BE204 and BE208 showed a higher potential because of the capility to antagonize to most of thirteen surveyed phytopathogens including Phomopsis longicolla, Neoscytalidium dimidiatum, and Phyllosticta cavendishii, based on the dual culture technique, causing significant damage on many crops in Vietnam. In addition, the two strains were also able to dissolve phosphate and zinc and produce enzymes hydrolyzing protein, starch and cellulose by also the spot streak technique. The results contributed the potential bacterial collection for the research and development of products from indigenous KSB in Vietnam. However, additional classifications as well as the safety of these selected strains need to be further investigated.