Symbiotic and Plant Growth Promoting Properties and Phylogeny of the Pea Rhizobium SCAU P10
[Objective]The objective was to isolate efficient pea rhizobia with strong symbiotic nitrogen fixation capacity,good resistance to environmental stress,effective plant growth promotion ability,and a wide host range.[Method]We evaluated the plant growth promotion ability and stress tolerance of the rhizobial strain SCAU P10 both in vitro and in field experiments conducted in Jintang and Jiange coun-ties,Sichuan Province,China,using conventional methods.The strain′s ability to nodulate and promote the growth of main pea varieties—"Changshouren""Zhongwan No.6""Wuxudoujian No.1"and"Yunwan No.91"—was assessed using hydroponics.The phylogenetic position of the strain was determined by se-quence analysis of the 16S rRNA gene,housekeeping genes,and symbiotic genes.[Result]Compared to the non-inoculated control,the yield of fresh pea seeds(green peas)of inoculated peas was 32.3%higher in Jintang County(P<0.05).The number of nodules,plant height,green manure yield(plant fresh weight),forage yield(plant dry weight),and nitrogen and potassium accumulation in inoculated peas were higher at both experimental sites(P<0.05).The strain exhibited strong acid and alkali toler-ance,growing at pH 4.0 to 10.0,and poor salt tolerance,growing only at 0.01%to 0.6%NaCl.It pro-duced indole acetic acid(IAA),a plant growth hormone,and demonstrated strong phosphorus and potas-sium solubilization abilities,solubilizing lecithin,calcium phosphate,ferric phosphate,and aluminum phosphate.Strain SCAU P10 nodulated all four major pea varieties in Sichuan.Comprehensive analysis of the 16S rRNA gene,housekeeping genes,and symbiotic genes identified the strain SCAU P10 as Rhizo-bium sophorae and indicated that its symbiotic genes had undergone horizontal transfer.[Conclusion]The pea rhizobium Rhizobium sophorae SCAU P10 forms effective symbiosis with the main pea varieties in Sichuan,solubilizes phosphorus and potassium,secretes IAA,and can grow over a wide pH range,thereby significantly promoting the growth and nutrient uptake of peas.This study provides a scientific ba-sis for the development,promotion,and application of rhizobial inoculants for peas in Sichuan.
field experimentrhizobia of pearesistance-promotingsymbiotic matchingphylogeny
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