Abstract
Silicate solubilizing bacteria (SSB) can play an efficient role in soil by solubilizing insoluble forms of silicates. In addition to this some SSB can also solubilize potassium and phosphates, hence increasing soil fertility and enhancing plant defense mechanisms. A total of 111 bacterial strains were isolated from various habitats of Pakistan and screened for solubilization of silicate, phosphate and potassium on respective media. Out of these, 35 bacterial isolates were capable of solubilizing either silicate, phosphate or potassium. Amongst these 7 bacterial isolates were capable of solubilizing all three minerals tested. The highest silicate (zone diameter 54 mm) and phosphate solubilization (zone diameter 55 mm) was observed for bacterial isolate NR-2 while the highest potassium solubilization was observed for NE-4b (zone diameter 11 mm). Dual culture antagonistic assays were carried out by using these bacterial isolates against four plant pathogenic fungi Magnaporthae grisae, Rhizoctonia solani, Altarnaria alternata and Macrophomina pheasolina. Mean zone of inhibition of these bacterial isolates against the four pathogenic fungi ranged between 4 mm to 39 mm. The largest zone of inhibition against all four bacterial strains was recorded for bacterial isolate NR-2 followed by NE-4b. These strains will be further investigated for their plant growth promoting activities in the future.
Highlights
Silicon (Si) enhances the growth, development and yield of many plants and is reported to decrease the incidence of many fungal diseases in different pathosystems by strengthening the cell walls and especially the outer membrane of epidermal cells in leaves increasing resistance to the penetration of pathogenic fungi [1] [2]
The highest silicate and phosphate solubilization were observed for bacterial isolate NR-2 while highest potassium solubilization was observed for NE-4b
The highest percentage of silicate solubilizing bacteria was observed in soil samples collected from Ayubia and Nathia Gali mountains where 100% bacterial isolates were silicate solubilizers while 64% of the total bacterial population was silicate solubilizers in soil samples obtained from Narowal fields which had been under routine cultivation of wheat and rice (Figure 1)
Summary
Silicon (Si) enhances the growth, development and yield of many plants and is reported to decrease the incidence of many fungal diseases in different pathosystems by strengthening the cell walls and especially the outer membrane of epidermal cells in leaves increasing resistance to the penetration of pathogenic fungi [1] [2]. Despite of its abundance in earth’s crust it is mostly present in insoluble forms that cannot be readily absorbed by plant roots [9] [10]. It remains in insoluble form unless solubilized by weathering action of rocks or biological activity of plant roots and microorganisms. The accumulated Si improves growth and yield of these plants but is involved in induction of systemic resistance (ISR) against pests and diseases [12]
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