Growth Improvement of Alfalfa (Medicago sativa L.) plants using native Sinorhizobium isolates

Rhizobia variants are groups of bacteria that fix nitrogen synergistically with root of Leguminaceae. The aim of this study is growth enhancement of Alfalfa plants using native Sinorhizobium isolates. Alfalfa plants were collected and confirmed by an expert. The nodules were crushed and inoculated to yeast extract manitol agar. The isolated bacteria were confirmed by inoculation test of alfalfa seeds in Leonard jar. Disinfected seeds of Alfalfa (Medicago sativa) var Hamedani were cultured in big pots (90 × 30 with 25cm high) in similar temperature, watering, light, and moisture. Plants in four tested pots were watered by bacterial suspension of four isolates of bacteria on third day and two cases were used as controls. After a six-week watering period by free nitrogen nutrient solution, plants were pulled out from soil and compared for their growth and nitrogen rate. Molecular confirmation of these isolates was carried out by amplification (PCR) of a specific gene named mucR. Control plants had no nodules and plants inoculated with Sinorhizobia had nodules. Ten plants of each pot were separated randomly and significant differences were observed between plant length, stem and root length of control and symbiosis plants. Dried weight of a hundred of control plants was 0.35g and for symbiosis plants were 1.12, 1.07, 0.79 and 0.78g. The rate of nitrogen was less in control than symbiosis plants. The results of this study show that four native isolated Sinorhizobium caused the enhancement of alfalfa plants and have potential for use as biologic fertilizer. It seems isolate No. 2 enhances the growth of plants more effectively than other isolated bacteria.