Characterization Of Xanthomonas Axonopodis Pv. Dieffenbachiae From Anthurium And Its Host Range Test In Zhejiang Province Of China

Bacterial blight of anthurium caused by Xanthomonas axonopodis pv. dieffenbachiae(Xad) is an important disease of anthurium(Anthurium andraeanum) in the world.It was first reported in Zhejiang province of China in 2008.In the present study the causal organism was characterized and its host range was tested. Fifty-two bacterial strains from anthurium and one strain from Aglaonema plants were isolated in Zhejiang Province.They were gram negative;yellow pigmented,with shiny and smooth,mucoid and convex colony morphology on the enrichment media. Pathovar identity of all 53 strains were determined as Xanthomonas axonopodis pv. dieffenbachiae(Xad) biotype B based on pathogenicity test and utilizing starch on cellobiose starch medium.Pathogenicity and host range tests were performed by spraying inoculation with 1×10~8 CFU/ml of bacterial suspensions.The pathogenicity test indicated that all bacterial strains produced characteristic bacterial blight symptoms on inoculated anthurium plants.The inoculated plants showed water-soaked lesions 2-6 days after inoculation,then the lesions enlarged rapidly and turned to brown or dark brown to produce necrotic lesions and typical blight lesions within one or two weeks.Some plants showed systemic symptoms of leaf chlorosis and rotted petioles.Host range tests were examined on 10 genera of plants in Araceae family of Aglaonema,Alocasia, Caladium,Dieffenbachia,Epipremnum,Homalomena,Monstera,Philodendron, Spathiphyllum and Syngonium.The results showed that all the Xad strains from Anthurium and Aglaonema tested caused the blight disease on these plants.The symptoms and severity of disease were varied with different plant genus.The Xad strains induced the most severe infection on Caladium bicolor ’Princess Libera’, Homalomena lindenii,and Syngonium podophyllum ’Albo-virens’,moderate infection on Aglaonema ’Butterfly’ and Dieffenbachia amoena while less infection on Alocasia cucullata,Epipremnum aureum ’Marble Queen’,Monstera obliqua,Philodendron ’Lemon Lime’ and Spathiphyllum clevelandii.The amplified fragment length polymorphism(AFLP) technique was used to determine the genetic variation among Xad strains in this study.Five selective primers combinations were selected according to number of polymorphic bands and polymorphism detected among the 6 representative strains selected.A total of 64 polymorphic bands were obtained using five selective primers combinations of EcoRI+A/MseI+A,EcoRI+A/MseI+T,EcoRI+C/MseI+A,EcoRI+C/MseI+G and EcoRI+C/MseI+T.The dendrogram generated by unweighted pair group method using arithmetic average(UPGMA) with Dice’s coefficient separated Xad strains from Zhejiang Province into two groups at 70%similarity.All of 51 strains in group 1 were isolated from Anthurium and one strain each from Aglaonema and Anthurium were in group 2.Cluster analysis within the strains from Anthurium found that all of 52 strains from Zhejiang Province and two strains from Thailand could be clustered together in the same group at 42%similarity.