Isolation,identification and characteristic analysis of soybean rhizobium Q7-3 strain
[Objective]To isolate,screen and identify rhizobium in Qinong 7 soybean of Heilongjiang Province,and study the effects of rhizobium on the growth and nodulation of Qinong 7 soybean.[Method]Rhizobium was isolated and screened by tissue isolation,and the phylogenetic analysis of rhizobium was carried out to clarify its species relationship.The effect of rhizobium on host nodulation ability was determined by tieback pot experiment.The salt-alkali tolerance of rhizobium was measured by liq-uid culture,and its utilization of the only carbon and nitrogen source was analyzed.[Result]A strain of rhizobium Q7-3 was isolated from Qinong 7 soybean and identified as Rhizobium giardinii by phylogenetic analysis.Compared with the control,the chlorophyll content of rhizobium Q7-3 was 29.37±0.53(SPAD value),which was significantly increased by 29.21％.Nitro-gen content was(12.87±0.53)mg/g,significantly increased by 30.93％;The number and fresh weight of root nodules were(17±5.72)and(0.13±0.01)g,respectively.The basic characteristics of rhizobium Q7-3 were analyzed and it was found that was not tolerant to salt stress.However,when the pH value in the culture environment was lower than 10.31,the growth and reproduction ability of rhizobium Q7-3 in the alkaline environment was still strong,but when the pH value was adjusted to 10.92,rhizobium Q7-3 hardly grew.Through the determination of carbon and nitrogen source utilization of rhizobium Q7-3,it was found that sucrose could be used as the only carbon source to provide reproductive nutrition for rhizobium Q7-3.When ammonium sulfate,tryptone and urea were the only nitrogen sources,rhizobium Q7-3 hardly grew or had weak reproductive ca-pacity.[Conclusion]Rhizobium Q7-3 is a fast growing rhizobium,which can promote nodulation of Qinong 7 soybean,and it has alkali resistance characteristics,and can effectively use sucrose as the only carbon source for growth and reproduction.
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