Molecular investigations on the causal agents of the die-back disease of Dalbergia sissoo Roxb. in Bangladesh

A new form of disease called “die-back” has been established in Dalbergia sissoo Roxb. trees. This disease has reached epidemic proportions in Bangladesh as well as in other countries of South Asia. Characteristic symptoms of this disease are necrotic leaves, wilting, successive thinning of the crown, stag-headedness and trunk lesions with gum flow. Affected trees usually die within several months. Fungi, bacteria and insects were reported to be associated with the die-back syndrome, but the causal agent(s) could not yet be identified. Therefore, in a collaborative approach with institutions of universities in Bangladesh and Germany interdisciplinary studies are initiated to analyse biotic and abiotic factors of this disease.

Late stage of the die-back disease of Dalbergia sissoo trees

The studies performed in the Biocentre Klein Flottbek are focussed on the detection and characterization of biotic agents from affected sissoo trees by molecular genetic techniques. Previous results from studies based on polymerase chain reaction (PCR), which revealed the association of phytopathogenic bacteria of the genus Pseudomonas with die-back disease (Tantau et al., 2005 [View]) shall be proven and confirmed in order to characterize the yet unknown species of Pseudomonas. Furthermore, the presence of other phytopathogenic bacteria and their role in the early stage of this disease shall be investigated. Since fungi, phytoplasms, viruses and even viroids are known to cause serious epidemics in woody plants, the presence of such agents will also be investigated by molecular genetic, immunological and biochemical techniques.

Scientists of the following institutions will be included in this cooperation: University of Hamburg, Biocentre Klein Flottbek and Institute of Soil Science; University of Dhaka, Department of Botany and Department of Soil, Water and Environment; University of Chittagong, Department of Botany, Bangladesh Forest Research Institute, Chittagong

Symptoms of sissoo die-back as found at a site near Bogra, Bangladesh: A: asymptomatic leaves. B: necrotic leaves. C: trunk lesions with dark exudates. D: entrance holes made by timber borers.