Microbiology Research Journal International

Aim: To evaluate the effects of endomycorrhizal fungi (AMF) and sulfur oxidizing bacteria as biofertilizers in presence of phosphors and sulfur as mineral nutrients on onion (Allium cepa L.) and maize (Zea mays L.) plants under field conitions.
Study Design: Identification of the used bacterial isolate and applied with endomycorrhizae individually or mixed culture as bioinoculum for onion and maize plants grown in sandy soil under field conditions.
Methodology: sequence analysis of 16S rRNA gene was applied to identify the bacterial isolate. Two field experiments were carried out in sandy soil to study the effect of AMF and the sulfur oxidizing bacterium individually or combination with the recommended dose of N, K and P (as rock phosphate or super phosphate) with or without sulphur element, on some growth parameters, nutrients content and yield parameter of maize and onion crops .
Results: Results indicated that the bacterial isolate A1 was identified as Acidithiobacillus ferrooxidans based upon the 99% of sequence similarity of 16S rRNA gene with the reference strain. Field experiments revealed that after 60 and 90 days, inoculation of onion plants with dual inoculation induced significant response in nutrient content, but this response was found after 90 days in case of maize plant. The maximum data of the sulphur oxidizing bacterial count, dehydrogenase activity and CO₂ evolution in the rhizosphere were obtained after 60 days of cultivation for onion and after 90 days with maize plants. Inoculation with Acidithiobacillus ferrooxidans A1+ AMF in amended soil with NK + S + R.P gave the best results in N, P and K content of onion crop, bulbs weight and pyruvic acid content. For maize plant, data indicated that added recommended dose of nitrogen, potassium, sulphur and rock phosphate (NK+S+R.P) with AMF + Acidithiobacillus ferrooxidans A1 inoculant led to highest significant increases of nitrogen , phosphours and potassium contents compared to other treatments. Also, there were high significant increases in dry weight of 100 seeds, ear weight and its nutrients content with the abovementioned treatment.
Conclusion: The dual application of a mixture of arbuscular mycorrhizal fungi and Acidithiobacillus ferrooxidans A1 seems to have the most pronounced effect on quality and quantity of onion bulbs and yield of maize plants with the recommended dose of sulphur and rock phosphate fertilizers in sandy soil.