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A new bacterial disease of strawberry is described. This disease, called bacterial leaf blight of strawberry, is characterized by dry, brown necrotic leaf spots and large brown V‐shaped lesions along the leaf margin, midrib and major veins. Symptoms are different from angular leaf spot of strawberry caused by the bacterium Xanthomonas fragariae. Strains of the bacterial leaf blight pathogen were characterized in a polyphasic approach by biochemical tests, fatty acid analysis, protein electrophoresis, serology, PCR, pigment analysis, ice‐nucleation activity, AFLP analysis, DNA:DNA hybridization, pathogenicity and host range tests, and compared with a number of reference strains of X. fragariae and other Xanthomonas species. Bacterial leaf blight strains formed a homogeneous group in all tests, completely different from X. fragariae. They were the only strains causing leaf blight of strawberry upon artificial inoculation into strawberry. Fatty acid and protein electrophoretic analysis showed that the strains belong to the phenon X. campestris (sensu latu, including pathovars now classified as belonging to X. arboricola). AFLP analysis and DNA:DNA hybridization further clarified their taxonomic position as belonging to X. arboricola. The name X. arboricola pv. fragariae is proposed for the bacterium causing leaf blight of strawberry with strain PD2780 (LMG 19145) as pathovar type strain. Criteria for routine identification are given and the taxonomic status is discussed.

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Strains of Xanthomonas campestris pv. pruni obtained from Prunus armeniaca. P. domestica, P. persica and P. salicina in different geographical areas were compared for pathogenicity, fatty acid and wholecell protein analysis. Four strains, one per each host plant, were inoculated at the same time, on the foliage of P. armeniaca, P. avium, P. persica and P. salicina cultivars. Mean content of fatty acids of X.c. pv. pruni strains were also compared with those of many strains of X.c. pv. campestris, pv. graminis, pv. hyacinthii, pv. pelargonii and pv. vasculorum. Strains showed a remarkable homogeneity in fatty acids content and whole‐cell protein profiles and principal component and cluster analysis did not reveal any grouping according to original host or geographical origin. However, X.c. pv. pruni strains can be grouped apart from the other X. campestris pathovars. There appears to be no pathogenic specialization among the strains tested, however, they varied in aggressiveness to host plants and host plant in susceptibility. The most of the strains were able to cross‐infect species other that from where they were originally isolated, although, P. avium did not show any symptom of disease. P. persica cv. Sentry and P. salicina cv. Globe Sun, recently licensed as resistant to X.c. pv. pruni. were infected, although to a lesser extent, by some strains.

A high-throughput antibody staining and washing system for large-scale routine indirect immunofluorescence testing was developed, using a robotic sample processor. The Tecan robotic sample processor (Miniprep 75/2, Tecan Benelux BV, Giessen, The Netherlands) was introduced, adapted and evaluated for its suitability for large-scale immunofluorescence screening of potato samples for the presence of the plant pathogenic quarantine bacterium, Ralstonia solanacearum. Throughput and quality of antibody-antigen reactions were compared to manual sample preparation for the immunofluorescence test according to a standard EU testing protocol, using 216 standard potato extracts, including 204 known negative extracts and 12 known positive extracts, and 24 positive control strain samples. Throughput of the Tecan robotic sample processor easily outcompeted manual staining of immunofluorescence slides. The robot was twice as fast as manual processing and is easily cost effective. With the robot 288 samples per day can be processed as compared to 144 samples per day with manual processing. No difference between quality of antibody-antigen reactions and readability of preparations under a microscope could be detected. The new Tecan robotic sample processor was found to be useful for high-throughput fluorescent antibody staining and washing in large-scale, routine indirect immunofluorescence testing.