The Study On The Stress-tolerant, Growth-promoting Ability And Nitrogen-fixing Effect Of Pea Rhizobia

Pea(Pisum sativum L.) is an important rotation crop in many arid and semi-arid parts of the world, the nitrogen benefits to the following crop are reported. Pea cultivation in arid and semi-arid agricultural regions is of great significance to rehabilitation ecological damage and inhibition soil degradation. At present time, the study on basic research including the investigation, collection and selection of resources for pea Rhizobium is less, which limit the use of pea-Rhizobium resources. In our study, 353 nodules has been collected from 8 different ecological regions in Gansu, Qinghai and Shanxi province, namely Dingxi, Wuwei, Qingyang, Linxia, Lanzhou, Huzhu, Ge'ermu and Zizhou. 364 pure cultivation were obtained by seperation and purification, the ability of stress tolerance, growth-promoting and nitrogen fixation of strains was evaluated after back-inoculation and soil selection of Rhizobium strains. Meanwhile, the the effect of soil factors of different ecological regions on strains was analyzed and discussed. The main results as follows:1. The status of pea root nodule is relevant to the climate conditions of sampling in different ecological regions. The nodules were less in Qingyang and Dingxi, and it was hard to collect nodule in Zizhou. There was a number of nodules in the looser and higher humidity soil in Wuwei, Lanzhou, Ge'ermu, Linxia and Huzhu. The efficiently spherical nodules, about 1cm in diameter, were found in Huzhu, Qinghai province.2. Inoculation with the selection strains had a role in promoting growth of pea. Compared with CK, the shoot dry weight increased by 2.9%-78.5%. The strains GDB27, GLC1 and QGW19 inoculated Yannong No.2 and Luwan, the shoot dry weight increased by over 57% compared to CK. Rhizobium inoculated pea increased soil nitrogen after harvest in Loessial soil and Irrigation-silting soil, NH4+N respectively 25.5 and 17.7 mg/kg, NO3-N 15.7 and 7.9 mg/kg.3. The stress-tolerant ability of pea rhizobia was closely related to their ecological environment. Pea rhizobia from salt and drought stress conditons was able to adapt to the salt and drought stress. The test on salt tolerance of 29 pea rhizobia showed 34.5% of the strains was resistant to 4.5% NaCl concentration medium. QGW19 obtained from Ge'ermu, GWC7.3 and GWWW16 obtained from Wuwei, GQZ5 obtained from Qingyang were better than other strains in stress-tolerant ability; Pea rhizobia with alkaline tolerance from northwestern generally was found, but the acid tolerance was weak, the alkaline tolerance of GWC7.3 was the better, followed by GQZ5, QGW19, GWWW16 and GLC1, the acid tolerance of GLC1 was the best, followed by QGW19 and GDW6; The study found pea rhizobia could be growth in -0.6mPa-0.2mPa of osmotic potential medium, when the osmotic potential was less than -0.6mPa, the growth of rhizobia were significantly inhibited, 48.3% of strains in the osmotic potential -1.0mPa could be growth, the drought tolerance of GDB27 and GQZ5 were found, followed by SY12, GWC7.3, SZ32 and GQC1. Strain GLC1 with the salt-tolerance, acid and alkalinity-tolerance, drought-tolerance was found.4. Phosphate solubilization ability of pea rhizobia were weak, but pea rhizobia were indicated with the good ability of secretetion auxin. QGW19 and GLC1 had a better phosphate solubilization ability than other strains, followed by SY3.1, XC3.1, GWC7.3, GQZ5; 10 strains, including QGW19, SY3.1, SY12, XC3.1, GWC7.3, GWWW16, GDB27, GQW28, GQZ5 and GLC1, were indicated with the good ability of secretetion auxin. QGW19, GLC1 and XC3.1 with both phosphate solubilization and secretetion auxin ability were found.5. The stress-tolerant and growth-promoting ability of pea rhizobia were closely related to the soil factors in seperation regions. The salt-tolerant ability of strains could be relatively increased by higher soil available nitrogen and alkaline soil, the drought-tolerant ability of strains could be relatively increased by higher soil available K content, and the acid-tolerant capacity of strains could be relatively increased by higher soil organic matter content, and the alkaline-tolerant ability of strains was mainly affected by soil pH; The phosphate solubilization ability of pea rhizobia could be relatively enhanced under high soil available P and weak alkaline soil conditions, whereas the ability of secretetion auxin could be relatively broadened under neutral soil pH and high soil P and low soil N conditions.6. The study also found pea Rhizobium with high nitrogen-fixing ability was usually from dry farming areas, such as, SY12,SY3.1 and GDB27 (N fixed 70mg/pot over).