Screening Endogenous Rhizobia From Alfalfa Seeds And Their Promoting Alfalfa Seedlings Growth Property

The endogenous rhizobia were islolated from alfalfa seeds, and some characteristics of the strains, such as rhizobia number, colony feature, physiological and biochemical reaction, adaptability, symbiotic nodule ability and nitrogen fixation were study by using MPN, ARA mehhod , tube and potted experiments. The main results obtained as follows.1. There are twenty-two potential strains isolated from various alfalfa seeds in different region and different stored time. The number of endogenous rhizobium changed distinctly with varieties, origin and stored time. That is, the number of endogenous rhizobia increased with the increase of stored time with 5 years. However, it decreased with the increase of stored time over 5 years. There were more endogenous rhizobia in the seeds from foreign district than that from our country. When inoculating test tubes and potted seedlings with endogenous rhizobia, the nodules appeared in host plant with nitrogenase activity.2. All of twenty-two strains can increase nodulation rate, nodulation amounts, nodule weight and biomass of alfalfa seedlings, however they show distinctly difference in intruding capability during inoculating with tube culture plants. The average nodulation rate was 66.67%. The average nodulation amounts of single seedling was 4.969 which increased 994.5% compared with control(0.454). And the strains show high average nodulation rate were SL01(12), SJ05(6.33), SX10(5), SL12(6.33), SR14(13.3), SL17(5)and ST21(5.67). The average nodule weight of single seedling was 6.989mg which increased 445.6% compared with control (1.281mg), and strains show high average nodule weight of single seedling were SL04(10.2mg), SJ05(11.8 mg), SZ11(11.9 mg), SL12(10.5 mg) and SR14(10.1 mg). The Average biomass of single seedling was 243.71mg which increased 129.7% compared with control (106.09 mg), strains show high stimulating tube culture plants growth were SJ05, SL12,SR14 and SL17.3. The characters of acid excreting, salt resistance, pH and high or low temperature tolerance of 22 strains were determined. The results shows that all strains can excrete acid, and about 40% (9 strains) strains can grow in media containing 10% NaCl and many of them can grow in media with pH5~pH11. About 6 strains can grow in media with pH4 and 14 strains can grow in media with pH12. 7 strains can resist high (40℃) or low(4℃) temperature. There are 6 strains(SM06, SA07, SA08, SX10, SD19 and SL20) show high...