Effects of Azotobacter and Pseudomonas inoculation in mitigate drought stress effects in Dactylis glomerata L.

One of the main causes of plant growth and development disorders is the presence of adverse environmental conditions such as drought, which leads to stress in plants and endangers their survival. Recent research, however, recommends the use of soil microorganisms, especially plant growth-promoting bacteria, which are involved in plant growth as well as the nutrient cycle in the soil, in order to reduce the negative effects of environmental stresses. The present study was conducted to investigate the effect of plant growth promoting bacteria on germination, growth and uptake of some nutrients in Dactylis glomerata L. under drought stress.

The research was conducted as a factorial experiment based on a completely randomized design. The first factor of biofertilizer application was considered at four levels, which were: control (C, no biofertilizer was used in this treatment), A = Azotobacter vinelandii, P = Pantoea agglomerans+Pseudomonas putida and A + P (combined use of Azotobacter and Pseudomonas). The second factor was drought stress, which was considered at three levels and included FC (field capacity), 0.4 field capacity (0.4FC) and 0.7 field capacity (0.7FC). For inoculation of biofertilizers (in powder form), half a gram of each pure fertilizer was dissolved 0.5 Li water and the seeds were impregnated with a solution. To apply drought stresses, soil field capacity was first determined using the weighting method. Then, based on the calculated base number for field capacity, the amount of water required to apply drought stress was determined. To measure germination percentage and rate, seedlings were counted daily. Plant species were harvested after 90 days. Stem and root length, plant dry weight and uptake of nitrogen, phosphorus, potassium, zinc, iron, manganese by the plant were measured. Multivariate analysis of variance was analyzed using SPSS software. Duncan test (5% level) was used to compare the means.

The results showed that the highest and lowest germination were related to treatment A at the level of 0.7FC and control treatment at 0.7FC, respectively. A+P treatment compared to the alone application of fertilizers had less effect on reducing drought stress on the plant germination. The maximum stem and root length and plant dry weight were related to Aztobacter treatment at 0.4 stress. While P treatment at 0.4 stress had the lowest root and stem length and plant dry weight. Maximum potassium uptake by the plant was measured in treatment A under FC conditions and the highest amount of iron and zinc in Pseudomonas application was measured at 0.7FC. A+P treatment at 0.4 stress showed the lowest absorption of iron, zinc and manganese. In general, the results showed that the use of Azotobacter is more effective in reduction of drought stress in D. glomerata L. compared to Pseudomonas. Also, separate use of the bio-fertilizers has a greater effect on reducing the effects of drought stress on the plant compared to combination treatments

In general, drought stress significantly reduced the growth of D. glomerata L. The use of growth-promoting bacteria by reducing the negative effects of drought improved growth and plant establishment in drought stress conditions. Azotobacter increased germination, plant dry weight, root and stem length. Pseudomonas also reduced the effect of drought stress on plant growth. Compared to Azotobacter, application of Pseudomonas had less effect on reducing the effects of drought on plant growth. In order to improve the growth and yield of the plant in dry conditions, inoculation of seeds of this plant with Azotobacter is recommended.