Plant growth-promoting rhizobacteria able to improve NPK availability: selection, identification and effects on tomato growth

Abstract

Nitrogen, P and K are essential macronutrients that are not readily available to plants. Rhizobacteria are able to convert these unavailable forms for subsequent uptake by the plant, diverse species have been characterized as N2 fixers, P solubilizers and capable to solubilize mineral K from unavailable forms. The objective of this study was to select rhizobacteria capable of improving NPK availability and promoting tomato (Solanum lycopersicum L.) growth. Fifteen strains were studied. Four strains were selected for their capacity to fix N2, three for their ability to solubilize P, and six for their capacity to solubilize biotite and K-feldspar, isolated from tomato, lentil, chili pepper, faba bean and lettuce crops in Andisol and Alfisol soils. Through 16SrRNA sequencing, selected strains were identified as Pseudomonas gessardi, P. koreensis, P. brassicacearum, P. marginalis, Acinetobacter calcoaceticus and Rahnella aquatica. Phosphorus solubilizing strains did not show a positive effect on plant growth or an increase in available soil P. The N2 fixing bacteria Tmt-16 strain increased root growth in 23.57%; maintained the highest N content in plant tissue, 2.60%, higher amount of N available in the soil, 2.95 mg kg-1 , and a higher content of N-NH4 + 1.95 mg kg-1. The K solubilizing strains Ls-C21, Ltj-62 and LsC-58 reached 17.0 to 19.0 mg kg-1 available K and 0.04 to 0.05 mg kg-1 exchangeable K (p ≤ 0.05.). These four endemic rhizobacteria can be potentially used as biofertilizers, allowing a reduction in the use of chemical fertilizers and a more sustainable production of tomatoes.

FE-SEM/EDX Based Zinc Mobilization Analysis of Burkholderia cepacia and Pantoea rodasii and Their Functional Annotation in Crop Productivity, Soil Quality, and Zinc Biofortification of Paddy

“…Microorganisms that produce organic acids facilitate the solubilization of bound phosphorus and potassium in the soil, thereby increasing the levels of these nutrients in the soil (Alori et al, 2017;Tian et al, 2021). Our study is justifiable with the previous studies in which bacterial treatments improved soil health by showing significant levels of organic carbon, nitrogen, phosphorus, and potassium (Adak et al, 2014;Reyes-Castillo et al, 2019). Finally, we rationalize our study and present its uniqueness from other studies based on the following aspects:(i) EDX spectrum and contact angle-based analysis were new techniques used to assert the Zn-solubilization potential of bacteria isolated from rhizospheric soil of underutilized crop, i.e., barnyard millet; (ii) decoding the effects of ZSB with low-cost ZnO source input on multiple agronomic and soil parameters at two different sites.…”

Bioinoculants as Promising Complement of Chemical Fertilizers for a More Sustainable Agricultural Practice

“…Besides, the inoculation possibly improved the translocation of S and K, whose amounts resulted higher in leaves than in roots, when compared to the control. Indeed, related P. koreensis strains was recently shown to feature relevant K solubilizing ability in soil, thus increasing the K bioavailability to plants (Reyes-Castillo et al, 2019;Adhikari et al, 2020). Very interestingly, the Fe content was significantly increased, and this effect might be correlated to the capacity of the same strain to produce siderophores, organic compounds which increase the Fe bioavailability (Scagliola et al, 2016).…”

Nematicidal Amendments and Soil Remediation

“…PGPR produce a wide range of plant growth substances, for instance gibberellins, auxins, cytokinins, and ethylene [154], and in combination with composts PGPR limit pest damage to plants [155]. Additionally, PGPR enhance the uptake of phosphorous and nitrogen by plants through nitrogen fixation and phosphate solubilization [156,157]. With respect to plant pathogens, 39 isolates of rhizobacteria recovered from different economic plants produced hydrogen cyanide and thus inhibited growth of Agrobacterium tumefaciens and affected viability of Meloidogyne incognita juveniles in vitro [158].…”