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[1] Bacterial black rot - Turkey: 1st report
[2] Clubroot - Nepal


[1] Bacterial black rot - Turkey: 1st report
Date: January 2008
Source: The American Phytopathological Society, Plant Disease 2008;
92(1): 176 [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-1-0176C>

[Reference: M Mirik et al: First outbreak of bacterial black rot on cabbage, broccoli, and Brussels sprouts caused by _Xanthomonas campestris_ pv. _campestris_ in the Mediterranean region of Turkey.
Plant Dis 2008; 92(1): 176; DOI: 10.1094/PDIS-92-1-0176C]

During warm and humid periods in the winters of 2004 to 2006, severe leaf necrosis and vein rot symptoms were observed on cabbage (_Brassica oleracea_ var. _capitata_ L.), broccoli (_Brassica oleracea_ var. _italica_ Plenck), and Brussels sprouts (_Brassica oleracea_ var. _gemmifera_ D.C.) in the Mediterranean region of Turkey. Symptoms were characterized by yellow, V-shaped areas of the leaf margin, with the internal tissue turning from brown to black.
Infected seedlings were also observed in commercial nurseries in Adana with a disease incidence [from] nearly 10 [up] to 25 percent.

A total of 20 isolates recovered from diseased leaf samples were selected at random to identify the causal organism. The isolates were identified as _Xanthomonas campestris_ pv. _campestris_. Fatty acid methyl ester (FAME) profile similarity indices ranged from 80 to 94 percent. Indirect ELISA [enzyme linked immunosorbent assay] further confirmed the identity of the pathogen in both pure culture and infected plant.

Pathogenicity of the isolates was tested on 5-week-old cabbage plants by spray inoculation. Sterile saline buffer was sprayed on negative control plants. Inoculated and control plants were maintained for 5 days. No symptoms developed on negative control plants. The bacterium was reisolated from inoculated cabbage plants and identified as _X. campestris_ pv. _campestris_ by FAME and an ELISA. To our knowledge, this is the 1st report of the occurrence and outbreak of _X. campestris_ pv. _campestris_ in the Mediterranean region of Turkey.

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[2] Clubroot - Nepal
Date: February 2008
Source: The American Phytopathological Society, Plant Disease 2008;
92(2): 317 [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-2-0317B>

[Reference: RD Timila et al: Severe and widespread clubroot epidemics in Nepal. Plant Dis 2008; 92(2): 317; DOI: 10.1094/PDIS-92-2-0317]

Cultivation of brassica vegetables has the highest potential for generating income among more traditional rice and maize farmers in Nepal. Among brassica vegetables, the most important are cauliflower (_Brassica oleracea_ var. _botrytis_ L.) and cabbage (_B. oleracea_ var. _capitata_ L.).

Although clubroot disease, caused by _Plasmodiophora brassicae_ Woronin, has been observed in Nepal since 1993, severe and widespread epidemics have been observed since 2004 in the Bhaktapur, Kathmandu, Lalitpur, and Palung Valley production areas. Typical disease symptoms are widespread, and disease severity has been particularly severe in the Kathmandu Valley and Palung/Daman area of the Makwanpur District. Many cauliflower fields in these areas have had as much as 100 percent yield loss between 2004 and 2006 with an estimated 40 percent overall loss from clubroot. Estimates from interviews with growers in the Palung production area during an intensive farmers' interaction program indicated that cauliflower production was reduced from 5-6 metric tons per household (1500 square meters) prior to 2004 to less than 300 kg per household in 2004 and beyond. The economic loss in this area alone was estimated at USD 1.4 million in 2004 and 2005.

Examination of transplant nurseries indicated that frequently more than 80 percent of the seedlings have symptoms of clubroot at the time of transplanting. Soil samples from throughout the production areas indicated that the sandy loam soils were predominately acidic (pH range of 4.2 to 7.2 with more than 90 percent below 6.0). Several management practices are being employed to reduce disease severity, including the use of clubroot resistant cultivars, raising the soil pH to above 7.0 by using dolomitic lime, testing of the fungicide flusulfamide and biopesticide (_Trichoderma viride_), and biofumigation and solarization of the nursery beds in an effort to reduce disease pressure on transplant material.

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[Black rot

The bacterium _Xanthomonas campestris_ pv. _campestris_ is the causal agent of black rot, which affects crucifers including cabbages, oilseed rape, and a number of weeds, which can serve as pathogen reservoirs. The disease affects primarily aboveground parts of plants at any stage of growth and causes high yield and quality losses, especially in tropical and subtropical regions. It is favoured by high humidity and warm temperatures. Symptoms may vary according to host and environmental conditions and generally include characteristic V-shaped lesions, leaf chlorosis, darkening of vascular tissue, extensive wilting and necrosis. Pre-existing fungal lesions may increase the susceptibility of crops to black rot by providing entry points for the bacteria.

The pathogen is seed-borne and can also be spread by mechanical means (including insects), plant debris, water, and wind. Disease management includes clean planting material (seed or transplanted seedlings), cultural practices, removal of weed reservoirs, and copper sprays. Some black rot resistant brassica cultivars are available.

Clubroot

Clubroot caused by the fungus _Plasmodiophora brassicae_ is a destructive soil-borne disease which affects nearly all cultivated, as well as many wild and weed members of the cabbage family. It is found worldwide and is most damaging in temperate regions and tropical highlands. The fungus enters root hairs and wounded roots, and multiplies rapidly, causing abnormal enlargement of the underground stem, taproot, or secondary roots. These roots often decay before the crop has matured, releasing many resting spores, which can survive for a decade in the absence of a susceptible host plant. Affected plants are stunted and may have discoloured purple leaves. Due to the distortion of the root, plants may wilt in dry weather and then recover at night.

Disease management is difficult due to the longevity of the spores and the inaccessibility of underground plant parts to fungicides.
Raising soil pH by addition of lime has been shown to be effective but is hardly practicable on large fields. Use of clean planting material is essential. The pathogen includes numerous pathotypes which makes it difficult to breed host cultivars with durable resistance.

_Trichoderma viride_ is a fungus used as a biocontrol agent for seed and soil treatment to prevent a range of fungal root diseases in many crops. It counteracts other fungi by the release of growth inhibitors and cell wall dissolving enzymes.

Maps
Turkey:
<http://media.maps.com/magellan/Images/TURKEY-W1.gif> and
<http://healthmap.org/promed?v=39.1,35.2,5>
Adana:
<http://www.mapzones.com/mapzones/maps/turkey/adana.php>
Nepal:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/nepal_pol90.jpg> and <http://healthmap.org/promed?v=28.3,83.9,5>
Districts and municipalities:
<http://www.un.org.np/reports/maps/npcgis/NatBio00004.jpg>

Pictures
Black rot on cabbage plant:
<http://www.nysaes.cornell.edu/pp/pp419/PP419Gallery/abawi/pages/cabbage%20black%20rot2.htm>
Black rot on cauliflower:
<http://vegetablemdonline.ppath.cornell.edu/Images/Crucifers/BlackRot_Cruc/BR_CrucFS8.jpg>
Clubroot on cabbage seedling:
<http://www.hri.ac.uk/site2/research/path/virus/clubroot.jpg>
Cabbage field with clubroot symptoms:
<http://vegetablemdonline.ppath.cornell.edu/Images/Crucifers/Clubroot/Clbrt_Crucfs1.jpg>

Links
Black rot fact sheets:
<http://ohioline.osu.edu/hyg-fact/3000/3125.html> and <http://vegetablemdonline.ppath.cornell.edu/factsheets/Crucifers_BR.htm>
_Xanthomonas_ taxonomy:
<http://www.bacterio.cict.fr/xz/xanthomonas.html>
Information on clubroot on crucifer crops:
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Crucifers_Clubroot.htm>,
<http://www.avrdc.org/LC/cabbage/clubroot.html>, and <http://www.omaf.gov.on.ca/english/crops/facts/85-043.htm>
_Plasmodiophora brassicae_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=214750>
_Trichoderma viride_ as biocontrol agent:
<http://www.soo.co.in/biotrico.htm>. - Mod.DHA]