Identification of Vicia faba Rhizobium and drought resistance verification in arid region of Qinghai

Abstract:

[Objective] To analyze the genetic diversity of Vicia faba Rhizobium in arid region of Qinghai,so as to obtain the Rhizobium strain with drought tolerance and matching V.faba varieties and thus promote the application of drought-tolerant Rhizobium of V.faba in arid region of Qinghai.[Methods] With the strain QHCD22 isolated from the arid region of Qinghai as the research subject,species identification and phylogenetic analysis were performed by morphology,physiological and biochemical characteristics,Biolog microbial identification system,16S rRNA gene sequencing and whole genome analysis.Further,polyethylene glycol (PEG)6 000 simulated drought stress,pot experiment and field plot trial were used to evaluate the drought resistance of the strain.[Results] Strain QHCD22 belonged to Rhizobium indicum.With the increased addition of PEG 6 000 to yeast mannitol agar (YMA) broth medium,the strain had an intermediate lethal osmotic potential under medium PEG concentration.But the number of viable strains increased under higher PEG concentration (osmotic potential of−0.6 mPa),and the turbidity of the strain rose from 61.48% to 69.42%,showing a strong drought tolerance.Pot experiment revealed that V.faba inoculated with the strain had higher plant height,GW/DW ratio,nodule number,nodule fresh weight,SPAD values,leaf relative water content (RWC),proline (PRO) content,superoxide dismutase (SOD) activity and root vatality (triphenyltetrazolium chloride,TTC) than that non-inoculated.In addition,under the condition of normal water,the indexes of the inoculated V.faba were higher than those of non-inoculated.The field plot trial indicated that the nitrogenase activity of strain QHCD22 was significantly elevated.Specifically,the nitrogenase activities of Qinghai 13 variety,Qingcan 14 variety and Maya variety ranged from 42.07 to 221.78 C₂H₄ nmol/(g·h),40.60 to 109.78 nmol C₂H₄ nmol/(g·h),and 33.41 to 643.15 C₂H₄ nmol/(g·h),respectively.Rhizobium inoculation promoted the increase of V.faba yield,with Qingcan 14 variety having a significant increase of 32.3%.[Conclusion] Strain QHCD22 belonged to Rhizobium indicum,which had certain drought-tolerant characteristics.The study confirmed that Rhizobium inoculation could improve the drought tolerance of V.faba,especially the drought-sensitive V.faba variety.Therefore the strain had potential application prospects.

Key words:Vicia faba;Rhizobium;phylogeny;drought tolerance evaluation