First Report of Dickeya chrysanthemi Causing Bacterial Soft Rot of Aloe vera in Sri Lanka

Abstract

Purpose: In September 2019, a rapidly spreading soft rot disease was observed in an Aloe vera cultivation in Puttlam District, Sri Lanka causing rotting of leaves and whole plant death, within three to five days. Identification of causal pathogen of soft rot was the main objective for effective management of the disease. The aim of this study was to isolate and molecular identification of causal pathogen of soft rot disease of A. vera and to confirm its pathogenicity. Research Method:The causal bacterium was isolated on Nutrient Agar medium and initially identified by colony characters. Pathogenicity was assessed by inoculation of leaves of potted A. vera plants with bacterial suspension of each isolates (x108 cfu ml -1 ). Bacterial DNA was extracted and subjected to PCR, using universal primers 27F and 1492R to amplify 16S rRNA region of the bacterium. The PCR products were sequenced and homology search was performed with GenBank database. Findings: Typical field symptoms began appearing after 24 hrs on inoculated plants, with the death of whole plant within two-three days after inoculation Based on PCR analysis, sequencing and homologysearch results, the causal pathogen of the bacterial soft rot disease of A. vera was identified as Dickeya chrysanthemi (former E. chrysanthemi). Sequences were deposited in GenBank for two bacterial isolates, kb (Accession No.MT028490.1) and kd (Accession No.MT028539.1). A BLAST search revealed 99 % identity with D. chrysanthemi from China (JF779681.1).Originality/Value: To our knowledge, this is the first report of D. chrysanthemi causing bacterial soft rot of A. vera in Sri Lanka. This finding will be very useful to formulating disease management strategies for bacterial soft rot of A. vera and to prevent outbreak of the disease.