Identification and characterization of Klebsiella oxytoca strains associated with wetwood disease of Morus trees

Abstract

The Morus plants with a wide range of features and properties are widely used for their edible fruits, medicinal and other ornamental purposes worldwide. In summer and spring of 2016, a wetwood disease was observed on Morus trees (Black mulberry, White mulberry and Red mulberry), in municipal lands and parks of Rafsanjan city (Kerman Province), Iran. Typical symptoms were wetwood symptoms characterized by canker, stem weeping and liquid exudates on trunk of infected trees. The causative agent of wetwood disease from the infected samples was identified as Klebsiella oxytoca based on its biochemical and phenotypic feature and confirmed using sequence analysis of atpD gene. Artificial inoculation of the isolated bacterial strain (predominant) on 1-year-old mulberry seedlings produced the necrotic symptoms on the inner bark of seedlings. To fulfill Koch’s postulates, the same bacteria were re-isolated from the diseased tissues and identified as Klebsiella based on colony morphology, phenotypic, and biochemical tests. Here, we described the characteristics of K. oxytoca strains as the causal agent of wetwood disease of Red mulberry (Morus rubra), White mulberry (Morus alba), and Black mulberry (Morus nigra) for the first time.