Tropentag, October 5 - 7, 2011 in Bonn "Development on the margin"

Pathogenicity of Soft Rot Bacteria from Potato on Tomato Plants, and Rapid Identification and Differentiation of the Pathogens by Restriction Fragment Length Polymorphism

¹Leibniz Universität Hannover, Institute for Plant Disease and Plant Protection, Germany
²Centre for Tropical and Subtropical Agriculture and Forestry (CeTSAF) - Tropenzentrum, Georg-August Universität Göttingen, Germany

Abstract

Out of 63 soft rot causing bacterial strains collected from potato fields in Syria and reference strains, 28 Pectobacterium and two Dickeya strains were subjected to a pathogenicity test on tomato (Lycopersicum esculentum) plants genotype L390. Twofold stem inoculation on 25 day-old tomato plants using 10 µl of 2.4*108 CFU ml^-1 suspensions of bacterial cells was performed by injection into stems at the third and fourth axial leaf basipetal. Disease severity was scored in six classes in two day intervals. Additionally, the pathogenicity of strains was tested by soil drenching with bacterial suspension (0.1 ml bacterial suspension per 1g substrate). The results confirmed that all Pectobacterium and Dickeya strains have the ability to cause soft rot disease on tomato stems. Pectobacterium carotovorum strains evoked severe symptoms, without significant differences between strains. P. atrosepticum strains showed a lower disease severity compared to each Pectobacterium and Dickeya strains. Pectobacterium strains were not pathogenic in soil inoculation, while both Dickeya's strains were soil pathogens.
Different sequence-based fingerprinting methods can properly assign strains to the appropriate species. Such studies require using different genes and an intensive statistical analysis. Restriction Fragment Length Polymorphism (RFLP) based on the information of one gene as a simple, rapid, accurate and inexpensive method was investigated for strain identification. In an in silico approach we identified a potential discrimination on basis of the malate dehydrogenase gene (mdh) to assign strains of each of the soft rot causing pathogens Dickeya spp., P. wasabiae, P.c. spp. odoriferum, P. betavascularum, P. atrosepticum and P. c. spp. carotovorum to the appropriate species. Two steps RFLP-mdh study produced specific and homogeneous banding profiles within the respective species and subspecies and was capable to differentiate 63 strains of Pectobacterium and Dickeya.

Keywords: , Dickeya, Pathogenicity, Pectobacterium, RFLP , soft rot

Contact Address: Shaza Nabhan, Leibniz Universität Hannover, Institute for Plant Disease and Plant Protection, Herrenhause Str. 2, D-30419 Hannover, Germany, e-mail: nabhanipp.uni-hannover.de