The role of some biofertilizers from the types of bacteria (PGPR) that stimulate plant growth in the growth, productivity and quality of tobacco plant (Virginia)

The research was conducted in the fields of Al-Hara village of Al-Muzairah, during the agricultural season 2021, by planting Virginia tobacco seedlings (Nicotiana tabacum L. Var. Virginia), according to a randomized complete block design, with three replications for each treatment. The aim of this research was to study the effect of four types of bacteria (PGPR) Azotobacter chroococcum, megaterium Bacillus, Rhizobium leguminosarum, Frateuria aurantia that stimulate plant growth on the growth, productivity and quality of tobacco plants. Some morphological and physiological characteristics were studied, such as the number of leaves (leaf/plant), total leaf area (m2/plant), yield of green and air-dry leaves (kg/dunum), and the content of air-dried tobacco leaves of biochemical compounds, total protein, soluble sugars, and nicotine. Where the inoculation with PGPR bacteria led to an increase in the number of leaves and the total leaf surface area of the plant, and gave the highest yield of green leaves (3250 kg / dunum) and dry leaves (700 kg / dunum), the largest length and width of the green and dry leaves cm, the highest percentage of transpiration, and the largest roundness factor per leaf, especially when inoculated with a mixture of isolates, and the qualitative characteristics of the dry tobacco leaf improved as the percentage of total protein and nicotine decreased and the percentage of total soluble sugars increased, especially in Bacillus megaterium and Rhizobium leguminosarum treatments.Soil analysis after the experiment showed a decrease in soil PH for all treatments inoculated with bacteria compared to the control, and an increase in its content of organic matter compared to the control soil, due to the role of organisms. A clear increase in the proportion of total nitrogen was also observed in treatments inoculated with nitrogen-fixing bacteria (Azotobacter chroococcum) alone or Mixed, and the soil of the treatments was characterized by an increase in its content of potassium, especially in the treatments inoculated with the bacterium Fraturia aurantia in a beneficial or mixed way compared to the uninoculated control, and a clear increase in the proportion of available phosphorus was observed in all the treatments inoculated with bacteria, especially in the inoculated with Bacillus megaterium compared to the control. Based on From the foregoing, it can be suggested to use the method of fertilization with a mixture of bacterial species on a larger scale, given its tangible role in stimulating growth in the Virginia variety and improving the quality of the resulting tobacco.