Abstract
Erwinia mallotivora was isolated from papaya infected with dieback disease showing the typical symptoms of greasy, water-soaked lesions and spots on leaves. Phylogenetic analysis of 16S rRNA gene sequences showed that the strain belonged to the genus Erwinia and was united in a monophyletic group with E. mallotivora DSM 4565 (AJ233414). Earlier studies had indicated that the causal agent for this disease was E. papayae. However, our current studies, through Koch’s postulate, have confirmed that papaya dieback disease is caused by E. mallotivora. To our knowledge, this is the first new discovery of E. mallotivora as a causal agent of papaya dieback disease in Peninsular Malaysia. Previous reports have suggested that E. mallotivora causes leaf spot in Mallotus japonicus. However, this research confirms it also to be pathogenic to Carica papaya.
Highlights
The genus Erwinia is classified in the family of Enterobactericeae, typically facultative anaerobic, gram negative rods possessing peritrichious flagella
E. papayae as causing papaya dieback in Malaysia
Gram-negative and rod-shaped bacteria with a peritrichous flagella arrangement were consistently isolated from water-soaked lesions (Figure 1)
Summary
The genus Erwinia is classified in the family of Enterobactericeae, typically facultative anaerobic, gram negative rods possessing peritrichious flagella. The common symptoms observed include greasy, water soaked lesions and spots on leaves, as well as foliar and angular lesions These lesions can lead to secondary infection, which can eventually cause the death of the papaya plant. E. papayae as causing papaya dieback in Malaysia They performed no significant biochemical tests to distinguish E. papayae and E. mallotivora, which are closely related species. They relied on two basic biochemical tests (oxidase and catalase) and the sequence similarity of the 16S rRNA gene to confirm E. papayae as a causal agent of papaya dieback in Malaysia. By combining phenotypic and genotypic information, we confirmed E. mallotivora as the causal agent of papaya dieback disease in Peninsular Malaysia
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