Kůdela V., Krejzar V., Pánková I. (2010): Pseudomonas corrugata and Pseudomonas marginalis associated with the collapse of tomato plants in rockwool slab hydroponic culture. Plant Protect. Sci., 46: 1-11.Plant pathogenic species Pseudomonas corrugata and P. marginalis were detected and determined in collapsed tomato plants in rockwool slab hydroponic culture in southern Moravia, Czech Republic. Surprisingly, P. marginalis was also determined before planting in apparently healthy grafted tomato transplants grown in hydroponic culture. Moreover, non-pathogenic P. fluorescens, P. putida, P. synxantha, and Stenotrophomonas malthophilia were identified. The Biolog Identification GN2 MicroPlate TM System (Biolog, Inc., Hayward, USA)was used for identification of bacterial isolates. Cultures of P. corrugata and P. marginalis were used in a greenhouse pathogenicity experiment. Seven weeks old tomato plants of cv. Moneymaker grown in sterilised perlite were inoculated into the stem with a hypodermic needle at one point above the cotyledon node. In inoculated tomato plants, disease symptoms were observed that included external and internal dark brown lesions around the inoculation site, watering and collapse of pith and sometimes also vascular browning and wilting of leaves. In comparison with P. marginalis, P. corrugata appeared to be a much stronger pathogen. Both tested Pseudomonas species were recovered from inoculated tomato plants. P. corrugata was found to move both upwards to the apex of the stem and downwards from the site of the inoculated stem into roots. When inoculated into potato tuber slices, some tomato strains of P. marginalis, P. fluorescens, P. synxantha, and Pseudomonas sp. produced soft rot. However, other strains of the same species were not able to macerate the potato tissue. It is concluded that P. corrugata and P. marginalis can be associated with the collapse of tomato crop in soilless culture grown in a greenhouse. This is the first report on P. corrugata in tomato plants in the Czech Republic. The role of plant pathogenic bacteria, fungal root rot and vascular pathogens and Pepino mosaic virus in the collapse of tomato plants is discussed.

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For the first time in the Czech Republic, bacteria identified as <I>Pseudomonas marginalis, Pectobacterium carotovorum</I> subsp. <I>carotovorum</I> and <I>Pseudomonas putida</I> were isolated from tubers of <I>Zantedeschia</I> spp. with symptoms of tuber soft rot. The symptoms occurred on mother tubers as well as on new daughter tubers of different calla lily hybrids with yellow spathe, calla lily cv. Mango with bright orange spathe and <I>Zantedeschia rehmanii</I> with pink spathe. The percentage of diseased plants of the total plants in the plot was around 10%. When inoculated into potato tuber slices, strains of <I>P. marginalis</I> and <I>P. c</I>. subsp.<I> carotovorum</I> produced soft rot. Pectolytic activity of <I>P. marginalis</I> strains was less intensive than that of the <I>P. c.</I> subsp. <I>carotovorum</I> strain. The results confirm that bacterial soft rot of <I>Zantedeschia</I> spp. may have several causes.

Pánková I., Krejzar V., Čepl J., Kůdela V. (2007): Detection of Clavibacter michiganensis subsp. sepedonicus in daughter tubers of volunteer potato plants. Plant Protect. Sci., 43: 127-134.Daughter tubers of volunteer potatoes were tested for their ability to maintain Clavibacter michiganensis subsp. sepedonicus (Cms). In different areas of the CR, volunteer potatoes were searched for in crops grown in rotation with potatoes and where one or two years before Cms had been detected and identified in samples of harvested seed or commercial potatoes using the test scheme in accordance to EC Directive 93/85/EEC. During May and June of 2005 and 2006, emerging or emerged plants of volunteer potatoes were collected at nine locations of Bohemia and transplanted to the experimental field in the Diagnostic Service Laboratory at Šluknov-Kunratice in Northern Bohemia. The daughter tubers of these plants were harvested and stored at 6°C for 1 month and then at 22°C for 3 months for multiplication of Cms cells. Samples of the daughter tubers were divided into 215 partial samples and tested for the occurrence of Cms at five terms which differed in length of storage time. The DAS ELISA test was used to detect Cms in the tuber samples. Cms was detected in eight of the nine potato volunteer tuber samples from different locations. The presence of Cms in positively tested tuber samples was confirmed using a pathogenicity test on eggplants (Solanum melongena). The optimal time for the detection of the pathogen in the harvested daughter tubers was between 4 and 10 weeks of storage at 22°C.

Conditions associated with an unusually high occurrence of burrknots in two young commercial apple orchards at two locations, Těšetice and Stošíkovice, South Moravia, the Czech Republic, were analysed. In the first orchard, planted in spring 2003, the occurrence of burrknot on trees of cvs. Early Smith, Jonagold and Gala on M.9 rootstock was evaluated. In the second orchard, planted in autumn 2002, cv. Gala on M.9 rootstock was assessed. Planting material used at each location was obtained from the same commercial propagator and had been established from the same propagation stock materials. Of 60 trees per cultivar surveyed in the first orchard, incidence of burrknots in cvs. Early Smith, Jonagold and Gala trees was 98, 97 and 92%, respectively. The burrknot severity (mean number of burrknots on above portion of rootstock) was significantly higher on Jonagold trees, i.e. 3.65, than on the other two cultivars. Of 60 Gala trees in the second orchard, symptoms of burrknot appeared on 73.3% of trees planted on a slight slope and 70.0% of trees planted on a plane. The burrknot severity was significantly higher on the Gala trees planted in the Těšetice orchard than in the Stošíkovice location. Burrknot incidence and incidence of root-suckers were the highest on Jonagold trees at Těšetice. However, correlations between burrknot number and number of root-suckers were not statistically significant. Five years after the tree planting, increased dying of Jonagold trees was recorded at Těšetice. Of 290 trees examined, 5.5% had died. On the rootstock portion of trunk, each dead tree exhibited burrknots associated with bark cankers that more or less girdled the trunks. Only sporadic occurrence of canker symptoms and no premature dying of young trees were observed at Stošíkovice. Attempts at isolation of the fire blight bacterium, <I>Erwinia amylovora</I>, and oomycete <I>Phytophthora</I> spp. from necrotic tissue surrounding burrknots on rootstocks were not successful. The stem associated apple tree viruses <I>Apple stem pitting virus</I> (ASPV) and <I>Apple stem grooving virus</I> (ASGV) were detected frequently in the rootstock and scion parts of cvs. Jonagold and Early Smith and less frequently in Gala cultivar. The virus positive trees included individuals both with various burrknot severity and without symptoms of burrknots. There were no correlations between the incidence of burrknots and the presence of ASPV and ASGV.