Potential Biofertilizers for Alkaline Soil: Bacteria Isolated from the Rhizosphere of Potatoes

Abstract

Root-associated microorganisms, which can be recruited specially by plants to cope with environmental stress under extreme conditions, are one of the major mediators of nutrient exchange between plants and the environment. To obtain more crop-beneficial microbes, rhizosphere bacteria of Désirée potatoes cultivated in poor and alkaline soil have been studied. The screening of 83 strains with incomplete identical 16S rDNA sequences showed that 47 strains produced indole acetic acid (IAA), with contents ranging from 0.2 to 42 mg/L, and seven strains were phosphorus-solubilizing, among which six strains significantly increased the growth rate of potato plants. Thirty-seven strains produced siderophore and four strains were zinc-solubilizing, among which three strains significantly alleviated the chlorosis of potato plants. In all of the isolates, the species Variovorax soli (ST98) and Cellulomonas biazotea (ST118) were first found to possess an IAA-secreting ability; the species Leifsonia aquatica (ST172) and Leifsonia naganoensis (ST177) and the genus Sutcliffiella (ST11) were first discovered to be capable of phosphorus solubilization; the species Chryseobacterium daecheongense (ST32) was the first reported to be capable of zinc solubilization; and the species V. soli (ST98), C. biazotea (ST118) and L. naganoensis (ST177) were first found to be capable of plant growth promotion. The discovery of multiple functional bacteria enriched the resources of plant growth-promoting bacteria and provided a foundation for biofertilizer production to improve soil conditions and crop production.