Abstract:

In the search for mineral potassium-solubilizing bacterial strains with multiple activities that may be relevant for a beneficial plant-microbe interaction–potassium solubilization, indoleacetic acids (IAA) and siderophore production, a total of 23 heterotrophic eugenic strains were isolated from rhizospheric soil in Shandong Province using a medium with feldspar as the sole K source. All strains produced IAA or their derivatives, and 43.5% of the strains displayed a very high level of siderophores. Seventeen percent of the strains showed better growth on feldspar and effects on solubilization of K in liquid cultures, suggesting that they were a valuable pool for discovering plant growth-promoting bacteria. Two bacterial strains, AFM2 and AC2, exhibited greater K release efficiency than other isolates. Amplified rDNA restriction analysis (ARDRA) revealed that all isolates could be divided into 11 groups at the similarity level of 60%. Most strains exhibited a unique 16S rDNA restriction pattern even when strains were isolated from the same soil type or plant species. Strains AC2 and AHZ1 of group XI were highly related toBacillus mucilaginosus, strain AFM2 of group IV shared 99% sequence homology with Agrobacterium tumefaciens.

Key words: mineral potassium-solubilizing bacteria, IAA, siderophores, genetic diversity