Components Identification And Degrading Bacteria Screening From Peach Root Bark

Peach(Prunus persica[L.]Batsch),Rosaceae,is an important stone fruit tree in China.Because of its bright color,good flavor,rich nutrition,it is widely loved by consumers.The continuous cropping obstacle of peach trees is a devastating disease that restricts the yield and quality of peach industry.At present,it is found that the accumulation of toxic substances produced by rotted root residuals in soil is one of the major cause for continuous cropping barriers.Therefore,this study mainly focuses on the composition and effect of decomposed liquid(DL),and the related degradation microorganisms in the rhizosphere.By using DL as sole carbon source or nitrogen source,1-2 rhizosphere microorganisms were speculated to be screened from the rhizosphere soil of peach tree to efficiently degrade the autotoxins of peach trees,which can provide a theoretical basis for alleviating or solving the peach replant disease.The main results of this paper are as follows:1.LC-MS was used to detect DL components.In the experiment,6 kinds of substances,including alcohols,lipids,flavonoids,organic acids,phytohormone,amino acids and their derivatives,were detectedand and many of them were reported as allelochemicals.The presence of CN~-was detected by the kit.2.Four strains with DL as the single carbon source and 3 strains with DL as the only nitrogen source were screened from rhizosphere soil of peach tree.Through colonies and cell morphology observation,combined with 16S rRNA gene sequencing,the strains were identified as Klebsiella oxytoca(WH-C1),Pseudomonas putida(WH-C2),Pantoea agglomerans(WH-C3),Flavobacterium johnsoniae(WH-C4),Enterobacter ludwigii(WH-N1),Acinetobacter calcoaceticu(WH-N2)and Pseudomonas nitroreducens(WH-N3).3.Lettuce seeds were used as a allelopathic indicator plant to test the toxicity of DL degradation products of different degrading bacteria.The results showed that the inhibition effect of DL degradation products of different degrading bacteria on the germination rate,germination potential and germination index was obviously decreased.The fresh weight and plant height of the lettuce seedlings in the WH-N3 treated group were significantly higher than those of the other treated groups.4.The optimum growth temperature of WH-N3 was 20?,and the optimum pH was6.0-7.0.When glucose and peptone were added,the growth rate of WH-N3 would increase significantly.5.WH-N3 can completely degrade benzoic acid with an initial concentration of about30 mg/L within 8 hours,and completely convert the cyanide with an initial concentration of 0.2 mg/L.Under laboratory condition,WH-N3 can survive for 3 months in continuous cropping soil without adding exogenous energy,and the amount of bacteria is about 10~6cfu/g soil.6.The peach seedling experiment showed that DL could seriously inhibit the growth of peach seedlings.With the addition of WH-N3,it could significantly alleviate the toxic effect of DL on peach seedling growth.