Plant Tissue Cult. & Biotech. 21(2): 101-113, 2011 (December)

Infectivity Assays and Sequence Analyses for Unassigned Pseudomonas Species as Putative Cause of Dieback Disease of Dalbergia sissoo Roxb. in Bangladesh¹

Hanny Tantau, Steffi Renk, Dorothee Schultz, Heidrun Meyer, Jana Schulze, Denise Palm, Annika Stubbe, Nayuf Valdez Aguirre, Rakha Hari Sarker, Sk. Shamimul Alam, Mihir Lal Saha, M. Salim Khan, M. Imdadul Hoque & Hans-Peter M?hlbach

Molecular Phytopathology and Genetics, Biocentre Klein Flottbek, University of Hamburg, Hamburg, Germany

Key words: Sissoo, Dieback, Pseudomonas, Fungal pathogens

Abastract

The causal agent(s) of dieback of sissoo (Dalbergia sissoo Roxb.) have not yet been identified unequivocally. Putative microbial pathogens (fungi and bacteria) were studied in dieback affected sissoo trees collected from Bangladesh, using plant pathological techniques combined with molecular tools. DNA based characteri-zation showed the presence of heterogeneous patterns of various fungi (mostly saprophytic). It did not support the hypothesis of Fusarium solani being the cause of sissoo dieback. In contrast, isolation and molecular characterisation of bacteria from dieback affected sissoo revealed the presence of Pseudomonas in 83% of the samples. Sequencing the gene of 16S ribosomal RNA, the rpoD-gene, the gacA-gene and the rnpB-gene strongly suggested that these isolates belong most probably to a still unassigned Pseudomonas species. Hypersensitivity response assays and infection studies using sissoo seedlings demonstrated their pathogenic potential.

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