Molecular Typing And Antibiotics Susceptibility Analysis Of Pseudomonas Syringae Pv. Actinidiae

Pseudomonas syringae pv.actinidiae(Psa)is the causal agent of kiwifruit bacterial canker.The main epidemic strain is biovar 3.Traditional resistant cultivars were found suspected infection during sampling.Whether the cause is related to new mutations in Psa is unclear.Due to lack of effective treatment,kiwifruit bacterial canker has become a worldwide problem.Therefore,clarifying the population structure of Psa and exploring its pathogenic mechanism are of great significance to the development of the kiwi industry.In this study,the pathogenic bacteria of the infected kiwifruit branches were identified by 16 S r DNA,and the biovar of Psa were identified using specific primers.The results showed that all Psa strains belonged to the biovar 3.Analysis of genetic variation of biovar 3 using repetitive element sequence-based PCR(rep-PCR)and multilocus sequence typing(MLST).The results showed that genetic information within the biovar 3 population was different.The results of two in vitro pathogenicity verification tests showed that the isolated strains could cause tobacco hypersensitive reaction,and significantly the color change of healthy ‘Hong Yang’ kiwifruit leaves,proving that isolated Psa has pathogenicity.The results of in vitro susceptibility tests of 11 antibiotics showed that 10 Psa strains exhibited the same antibiotics resistant phenotype against 3 antibiotics,indicating that they were multi-drug resistant bacteria.Whole genome sequencing was performed on a biovar 3 strain(named GX05)to obtain draft whole genome.Its virulence genes,antibiotics resistance genes and genes related to pathogen host interaction were preliminary analysis and prediction.Results showed that it carried a large number of virulence genes in which reduced virulence genes are most.The annotation results show that its pathogenicity may be related to the iron transport system and type III secretion system,and its antibiotics resistance may be related to multidrug resistance efflux pump system.In summary,this study has preliminary explored the population information of Psa and predicted its pathogenic mechanism and antibiotics resistance mechanism,so as to provide a theoretical basis for further study on its pathogenesis and rational drug use.