Abstract
Phosphate-solubilizing bacteria (PSB) have the ability to solubilize insoluble phosphorus (P) and release soluble P. Extensive research has been performed with respect to PSB isolation from the rhizospheres of various plants, but little is known about the prevalence of PSB in the grapevine rhizosphere. In this study, we aimed to isolate and identify PSB from the grapevine rhizosphere in five vineyards of Northwest China, to characterize their plant-growth-promoting (PGP) traits, evaluate the effect of stress on their phosphate-solubilizing activity (PSA), and test their ability to stimulate the growth of Vitis vinifera L. cv. Cabernet Sauvignon. From the vineyard soils, 66 PSB isolates were screened, and 10 strains with high PSA were identified by 16S rRNA sequencing. Sequence analysis revealed that these 10 strains belonged to 4 genera and 5 species: Bacillus aryabhattai, B. megaterium, Klebsiella variicola, Stenotrophomonas rhizophila, and Enterobacter aerogenes. The selected PSB strains JY17 (B. aryabhattai) and JY22 (B. aryabhattai) were positive for multiple PGP traits, including nitrogen fixation and production of indole acetic acid (IAA), siderophores, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, chitinase, and protease. JY17 and JY22 showed strong PSA under stress conditions of high pH, high salt, and high temperature. Therefore, these two isolates can be used as biofertilizers in saline-alkaline soils. The inoculation with PSB significantly facilitated the growth of V. vinifera cv. Cabernet Sauvignon under greenhouse conditions. Use of these PSB as biofertilizers will increase the available P content in soils, minimize P-fertilizer application, reduce environmental pollution, and promote sustainable agriculture.
Highlights
Phosphorus (P) is one of the major macronutrients important for the growth and development of plants, and it is involved in essential metabolic pathways, including photosynthesis, biological oxidation, nutrient uptake, and cell division (Illmer & Schinner, 1992; Gupta et al, 2012)
P-solubilizing activity is related to the microbial production of organic acids, which chelate the cation bound to phosphate, thereby converting it to a soluble form (Sagoe et al, 1998; Rashid et al, 2004; Lugtenberg & Kamilova, 2009)
A significant negative relationship was observed between the amount of soluble P and pH in the culture medium (R2=0.953)
Summary
Phosphorus (P) is one of the major macronutrients important for the growth and development of plants, and it is involved in essential metabolic pathways, including photosynthesis, biological oxidation, nutrient uptake, and cell division (Illmer & Schinner, 1992; Gupta et al, 2012). A large portion of the total P in the soil is insoluble and unavailable for plant uptake. A deficiency in soluble P in many agricultural soils is one of the major factors hampering crop production worldwide (Arcand & Schneider, 2006; Yang et al, 2012). It is important to explore alternative ways to improve the status of P in soils, such as the utilization of biofertilizers
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