The Screening of Potassium- and Phosphate-Solubilizing Actinobacteria and the Assessment of Their Ability to Promote Wheat Growth Parameters

Abstract

Soil fertility and plant nutrition require an adequate management of essential macronutrients such as potassium (K) and phosphorus (P), which are mandatory for plant development. Bioleaching of K and P bearing minerals improves their chemical weathering and increases the performance of the biofertilization strategies. In this study, in vitro and greenhouse experiments were carried out to investigate P and K solubilization traits of nine Actinobacteria (P13, P14, P15, P16, P17, P18, BC3, BC10, and BC11) under fertilization with rock phosphate (RP). K and P solubilization were evaluated on Alexandrov and NBRIP media containing mica and six RP samples, respectively. The actinobacterial strains were able to solubilize K in Alexandrov medium supplemented with RP. However, when soluble P was used instead of RP, only four strains of Actinobacteria (Streptomyces alboviridis P18–Streptomyces griseorubens BC3–Streptomyces griseorubens BC10 and Nocardiopsis alba BC11) solubilized K. The solubilization values of K ranged from 2.6 to 41.45 mg/L while those of P varied from 0.1 to 32 mg/L. Moreover, all strains were able to produce IAA, siderophore, HCN, and ammonia and significantly improved the germination rate and the vigor index of wheat. The pot experiments revealed that four strains (Streptomyces alboviridis P18, Streptomyces griseorubens BC3, Streptomyces griseorubens BC10, and Nocardiopsis alba BC11) significantly improved the growth parameters of wheat, namely root length (1.75–23.84%), root volume (41.57–71.46%), root dry weight (46.89–162.41%), shoot length (8.92–23.56%), and shoot dry weight (2.56–65.68%) compared to the uninoculated control. These findings showed that Streptomyces griseorubens BC10 and Nocardiopsis alba BC11 are promising candidates for the implementation of efficient biofertilization strategies to improve soil fertility and plant yield under rock P and rock K fertilization.

Characterization of Plant Growth-Promoting Traits and Inoculation Effects on Triticum durum of Actinomycetes Isolates under Salt Stress Conditions

“…Our findings show that generally, the maximum solubilization rate occurred in the presence of a certain amount of NaCl, depending on the strain, and lower without NaCl. These findings are in accordance with previous studies; many bacteria require NaCl for better solubilization of inorganic phosphate [64,65] and microorganisms originating from saline soils are a valid tool to improve the availability of phosphorus in soil and improve wheat growth parameters [66].…”

The Impact of Growth-Promoting Streptomycetes Isolated from Rhizosphere and Bulk Soil on Oilseed Rape (Brassica napus L.) Growth Parameters

“…The strain KmiICH17A097 (11.9 mm) from bulk soil, strain Streptomyces misionensis KmiRC20A118 (13.1 mm) and strain KmiRC20A120 (12.7 mm) from rhizosphere soil of oilseed rape showed low phosphate solubilisation index values, and we did not observe this ability in strains from the maize rhizosphere (Table 5). Similar results have been reported in studies where bacterial strains tested on Pikovskaya agar showed a low solubility index [73][74][75]. The ability of the same bacteria to dissolve phosphates on solid agar and liquid medium differs; some studies have found that the bacteria show a considerably higher phosphate production in liquid medium [76,77].…”

Multiple Potential Plant Growth Promotion Activities of Endemic Streptomyces spp. from Moroccan Sugar Beet Fields with Their Inhibitory Activities against Fusarium spp.

“…griseorubens BC3, S . griseorubens BC10 and Nocardiopsis alba BC11 had the ability to solubilize K in AMM and amounts of K ranged from 2.6 to 41.45 mg/L after 11 days of cultivation [ 23 ]. Reyes-Castillo et al [ 59 ] reported that Bacillus mucilaginosus dissolved K from motmorillonite, kaolinite and K-feldspar, showing values of 90 to 140 mg/L after 7 days of cultivation.…”

“…K-solubilizing bacteria (KSB) have attracted more attention because of their ability to increase plant growth and yield [ 17 ]. However, very few studies have demonstrated these abilities of KSB [ 18 , 19 , 20 , 21 , 22 , 23 ]. To date and to the best of our knowledge, this is the first time that such a study has been undertaken, especially on the endemic Actinobacteria from sugar beet rhizospheres in the Beni-Mellal region with these PGPR criteria.…”