Diversity and Phosphate Solubilization Efficiency of Phosphate Solubilizing Bacteria Isolated from Semi-Arid Agroecosystems of Eastern Kenya

Abstract

Phosphorus (P) is a major nutrient required for plant growth but it forms complexes with other elements in soil upon application. A cost-effective way of availing P to plants is by use of Phosphate Solubilizing Bacteria (PSB). There is a wide range of PSB suited for diverse agro-ecologies. A large part of Eastern Kenya especially the lower altitude regions are semi-arid with nutrient depleted soils and predominated by low-income smallholders farmers who do not afford costly inorganic fertilizers. To alleviate poor soil nutrition in this agroecosystem, we sought to study the diversity of phosphate solubilizing bacteria and their phosphate solubilization efficiency. The bacteria were selectively isolated in Pikovskaya’s agar media. Bacterial colonies were enumerated as Colony Forming Units and morphological characterization determined by analyzing morphological characteristics. Genetic characterization was determined based on sequencing of 16S rRNA. A total of 71 PSB were isolated and they were placed into 23 morphological groups. Correlation analysis showed a negative correlation between phosphate solubilizing bacteria and the levels of phosphorus, iron, calcium, magnesium and soil pH. Analysis of 16S rRNA sequences revealed that the genetic sequences of the isolates matched the strains from the genera Burkholderia, Pseudomonas, Bacillus, Enterobacter, Pantoea, Paraburkholderia, Cronobacter, Ralstonia, Curtobacterium, and Massilia deposited in NCBI Database. Analysis of Molecular Variance showed that variation within populations was higher than that of among populations. Phosphate solubilization index values ranged between 1.143 and 5.883. Findings on biodiversity of phosphate solubilizing bacteria led to identification of 10 candidate isolates for plant growth improvement and subsequently, bio-fertilizer development.

Toxicity of Herbicide, Paraquat Dichloride and Insecticide, Lambda-cyhalothrin on Phosphate Solubilizing Bacteria, Pantoa dispersa in Aquatic Ecosystems

“…The total count of phosphate solubilizing bacteria ranged from 3.6×10 3 ± 0.00 CFU/ml (3.55 Log CFU/g) to 4.8×10 5 ± 0.12 CFU/g (5.68 Log CFU/g) as the fresh water recorded the least count of phosphate solubilizing bacteria while the highest count was recorded in the soil sample. Result of the count in this study is similar to the population recorded by Kirui et al [17] in the study to determine the diversity of phosphate solubilizing bacteria from semi-arid agroecosysterm of eastern Kenya in which the population of culturable PSB ranged from 1.3×10 4 to 3.63×10 4 CFU/g. The organism, Pantoa dispersa was identified from biochemical results indicating; Gram negative rod, indole negative, citrate positive, oxidase negative, catalase negative, non-motile, MR negative, Starch negative, glucose negative and macroscopially, yellow colonies were observed.…”

Overview of biofertilizers in crop production and stress management for sustainable agriculture

“…They are beneficial bacteria that effectively mobilize the soluble phosphorus and mineralization of the organic phosphorus compound, both are unavailable form of phosphorus. Bacillus, Pseudomonas , and Rhizobium are representative phosphorus-mobilizing microorganisms (PMB) (Kirui et al, 2022 ). Three different mechanisms have been reported for this process.…”

Tomato Production under Synergistic Application of Phosphate Solubilizing Bacteria and Phosphate Amendments

“…Due to the rapid fxation nature of phosphate ions, most of the applied fertilizer [2] converted to unavailable residues [7]. Diferent complications with the defciency of plant available nutrients [8], the efcacy of applied chemical fertilizers and other constraints including production cost, environmental issue, and production demand calls organic matters and biological inputs for sustainable crop production [9][10][11][12]. As indicated in Rilling et al, 2019 [13] diverse microbial groups including benefcial microbes are rich in the root zone competing for root exudates.…”

“…Generally, Verma et al 2019 [5] summarized that PGPR benefts plants in four major processes, namely, plant growth enhancement, biocontrol, stress management, and soil renovations by rhizoremediation. PSB are known PGPR [3,12] with multidimensional benefts [17] including broad host range interaction, accessing nutrients, phytohormone induction, stress alleviation, biocontrol activity, resistance enhancement, and eco-friendly approach [8].…”

“…As a result, smallholder farmers increased fertilizer application season-toseason [23]. Tough, the production cost is heightened [12], soil fertility maintenance (nutrient amendment) and proper farm practice (ploughing, irrigation, conservation and weeding) are essential to increase production. Despite the increasing trends overtime, the proper chemical fertilizers application rate is relatively low [24].…”