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Introduction
Jan Nechwatal currently works at the Institute for Plant Protection, Bavarian State Research Center for Agriculture, and heads the bacteriology diagnostic lab. Jan does research in Plant Pathology, Bacteriology and Mycology, and has a long record of experience in Pythium, Phytophthora and other oomycetes, as well as in phytobacteriology. His lab mainly deals with routine diagnosis of bacterial plant pathogens and is constantly seeking to improve the detection and identification methods in use.
Current institution
Additional affiliations
November 2014 - present
January 2012 - December 2012
Position
- Researcher
Description
- Project: Studies on Aphanomyces cochlioides and the causes of „girth scab“ disease of sugar beet
September 2011 - October 2014
Position
- Researcher
Description
- Project: Phytophthora infestans control in organic farming
Publications
Publications (80)
Validation data is presented for a conventional PCR test that specifically detects the quarantine pathogen Pantoea stewartii subsp. stewartii in maize leaf and seed samples and does not cross‐react with the non‐pathogenic P. stewartii subsp. indologenes . The PCR tests currently recommended by the EPPO Diagnostic Protocol PM 7/60 (2) for initial sc...
A distinctively pink soft rot has been repeatedly observed on samples of root parsley (Petroselinum crispum var. tuberosum) from different regions in Germany since 2015, and pink pigmented bacteria were consistently isolated from these roots. As indicated by their biochemical properties and sequences of the gapDH and rpoD genes, the parsley strains...
In spring 2019, Capsicum annuum plants, var. Jalapeno M, from an organic greenhouse production site in Bavaria, Southern Germany, showing typical symptoms of a bacterial leaf spot disease were sent in for diagnosis. The plants were a few weeks old, approx. 15 cm in height, and displayed different stages of leaf necroses. Spots were typically round,...
Phytophthora cinnamomi and P. cactorum were detected in soil samples from a Vaccinium corymbosum stand in southern Germany. Both species were virulent in an underbark inoculation assay and have not been reported from highbush blueberry in Germany before. While P. cactorum is a widely distributed species in nurseries and (semi)natural habitats like...
A method is described that generates DNA extracts suitable for the detection of Clavibacter sepedonicus and Ralstonia solanacearum in potato samples, without the need for laborious, time‐consuming extraction protocols or expensive kits and laboratory equipment. Furthermore, a multiplex test is presented that allows the simultaneous detection of bot...
Between 2010 and 2015, an extensive survey of Phytophthora diversity was performed
across Portugal. Baiting and direct isolation tests obtained 48 Phytophthora taxa in 62 of 70 forest stands (89%) from 148 of 302 rhizosphere soil samples (49%) and 25 of 29 tree species (86%), and from bark cankers of Alnus lusitanica and Fagus sylvatica; from 33 of...
Salix appendiculata, eine in der Regel als größerer Strauch, selten auch als kleiner, bis maximal 6 m hoher Baum wachsende Weide, kommt vor allem in den Alpen (von der Bergstufe bis über die alpine Waldgrenze), im Schweizer Jura, im nördlichen Alpenvorland sowie in den Höhenlagen einiger Mittelgebirge (Schwarzwald, Bayerischer Wald) natürlich vor....
An analysis of incidence of Phytophthora spp. in 732 European nurseries producing forest transplants, larger specimen trees, landscape plants and ornamentals, plus 2525 areas in which trees and shrubs were planted, is presented based on work conducted by 37 research groups in 23 European countries between 1972 and 2013. Forty-nine Phytophthora taxa...
Die Kraut- und Knollenfäule der Kartoffel (Phytophthora infestans) kann im ökologischen Kartoffelanbau hohe wirtschaftliche Einbußen verursachen. Sie kann bislang nur durch die Anwendung von Kupfer-Präparaten effektiv reguliert und bekämpft werden. Die Anreicherungsproblematik im Boden und mögliche negative Auswirkungen auf Nicht-Ziel-Organismen ma...
In organic potato production, late blight caused by Phytophthora infestans can cause severe losses in potato yield and quality. Currently, it can only be effectively controlled by the use of copper fungicides in some countries. In the course of a project aiming at the reduction of copper usage potential copper-free products against late blight for...
Potato late blight (Phytophthora infestans) causes severe losses in potato yield and quality in organic production. Still, the disease can only be effectively controlled by the application of copper fungicides. Due to copper accumulation in the soil and expected detrimental effects on the environment and non-target organisms, a reduction in the usa...
Poster at EuroBlight Workshop, Brasov, Romania (May 10-13, 2015).
A selection of copper-free products for the control of late blight (Phytophthora infestans) infections in organic potato production was tested for their suitability as a tuber treatment in both laboratory and field trials. Both a storage and a growth test were performed under controlled conditions in the lab/ greenhouse using artificially inoculate...
Rhizoctonia solani AG2-2IIIB is the causal agent of late crown and root rot in sugar beet. In a 4-year field study we analyzed the impact of different plant residue management systems of sugar beet and maize as well as of growing wheat (non-host) and different maize varieties on the soil inoculum density of R. solani. Sugar beet remains were either...
Roots, collars and rhizosphere soils from diseased boxwood saplings (Buxus sempervirens) from German and Romanian nurseries were shown to be colonized by a Phytophthora species (P. taxon Buxus) closely resembling the recently described species P. himalsilva. After comparison of both taxa using morphological, phylogenetic and pathogenicity data the...
In organic potato production, late blight caused by Phytophthora infestans can only be effectively controlled by the use of copper fungicides. In the course of a project aiming at the reduction of copper usage potential copper-free products for the control of late blight are being identified. Since infected seed tubers are among the main sources of...
A set of isolates closely related to the reed pathogen Pythium phragmitis was found among Pythium strains obtained from reed (Phragmites australis) soil and plant samples in Germany and Switzerland. These isolates consistently differed from P. phragmitis at 6, 6 and 3 nucleotide positions in the rDNA internal transcribed spacer region, the β-tubuli...
Potato late blight epidemics, caused by Phytophthora infestans, will usually start from infested seed potatoes introduced into the fields. Recent PCR analyses have shown that on average 10% of the seed potatoes are latently infected with P. infestans. In the field, as soon as soils are sufficiently moist, primary stem infections will develop from t...
Rhizoctonia solani AG2-2IIIB is the causal agent of late crown and root rot in sugar beet (Beta vulgaris subsp. vulgaris). In a 4-year field study we analyzed the effect of different corn cultivars and agricultural practices on the soil inoculum density of R. solani. Moreover, we report on the evaluation of different on- and off-site monitoring sys...
Rhizoctonia solani AG2-2IIIB, the casual agent of late crown and root rot in sugar beet (Beta vulgaris subsp. vulgaris), causes great losses in Germany. Due to R. solani’s soilborne nature it is very difficult to quantify fungal inoculum densities in the soil and hence to estimate the outbreak risk of Rhizoctonia root rots. So far, no monitoring sy...
Early primary stem infections developing from infected seed tubers are the most important starting points for early and massive late blight epidemics. As revealed by PCR analyses, about 10% of the seed tubers are latently infested with P. infestans, and thus carry the inoculum of the pathogen. In conventional farming, primary infections can be effe...
A selection of copper-free products for the control of late blight (Phytophthora infestans) infections in organic potato production was tested in both laboratory and field trials. Among the most promising preparations was a commercial garlic product and a knotweed product, of which the former was almost as effective as copper in in vitro assays. St...
Since its first isolation from Salix roots in 1972, isolates of a sexually sterile Phytophthora species have been obtained frequently from wet or riparian habitats worldwide and have also been isolated from roots of Alnus and Prunus spp. Although originally assigned to Phytophthora gonapodyides on morphological grounds, it was recognized that these...
Large‐scale Phytophthora surveys in (1) forest nurseries, advanced tree nurseries, horticultural nurseries
and ornamental nurseries and (2) forest, riparian, amenity, landscape and ornamental plantings and
horticultural plantations were conducted by 32 research groups in 21 European countries between 1977
and 2012 with most surveys dating from afte...
The term ‘girth scab’ describes a chronic disease of sugar beet roots ( Beta vulgaris ssp. vulgaris ) for which the causes still remain unclear. While pathogenicity of the oomycete Aphanomyces cochlioides to sugar beet has been known for along time, most practical guides and other professional literature refer to actinobacteria as the causal agents...
In recent years, Common ash (Fraxinus excelsior) throughout Europe has been severely impacted by a leaf and twig dieback caused by the hyphomycete Chalara fraxinea. The reasons for its current devastating outbreak, however, still remain unclear. Here, we report the presence of four Phytophthora taxa in declining ash stands in Poland and Denmark. Ph...
During and after prolonged periods of rainfall in late spring, blighted young twigs of European beech (Fagus sylvatica) were frequently observed in several beech stands in south-western and southern Germany. Long and short shoots of young understorey trees or lower branches up to 1.5 m above the soil level were affected. Symptoms also occurred regu...
1. Leaf litter breakdown by shredders in the field is affected by leaf toughness, nutritional value and the presence of secondary compounds such as polyphenols. However, experiments involving the use of single fungal strains have not supported the assumption that leaf parameters determine food selection by shredders perhaps because of a failure to...
Die Alpenrebe ist ein etwa 1-2 m hoher, mit den Blattstielen rankender Schlingstrauch, der in den Alpen, den Karpaten und den Apenninen in Höhen bis über 2000 m vorkommt. Die häufig getrennt betrachtete Clematis alpina ssp. sibirica und andere Subspecies besitzen separate Areale im nördlichen Russland, Sibirien, in Nordasien sowie in Nordamerika. S...
In this study dealing with the development of management strategies for P. ramorum in Rhododendron stands several plant protection and fertilizer products were tested for their suitability to control this pathogen on Rhododendron. Tests were conducted on young potted plants and abscised leaves, using the following products: phosphite (Nutri-Phite®...
The interaction of microbial colonization with leaf litter breakdown by the shredder Gammarus roeselii was studied in the littoral of large Lake Constance. In a first step we studied selective feeding of gammarids on leaf litter from three different treatments. Littoral exposed, tap water exposed, and autoclaved leaves were offered to G. roeselii i...
In a 3-year-study, we analysed the population dynamics of the reed pathogen Pythium phragmitis and other reed-associated oomycetes colonizing fresh and dried reed leaves in the littoral zone of a large lake. Oomycete communities derived from internal transcribed spacer clone libraries were clearly differentiated according to substrate and seasonal...
Pythium species are economically significant soilborne plant pathogens with worldwide distribution, causing seedling damping-off
or root rot diseases. Pythium phragmitis is a newly described pathogen of common reed (Phragmites australis), widespread in the reed-belt of Lake Constance, Germany. It is highly aggressive towards reed leaves and seedlin...
A comparison of oomycete diversity in reed stands (Phragmites australis) of Lake Constance, Germany, and maize fields close-by provided evidence for the occurrence of natural hybridisation between Pythium phragmitis, a newly described reed pathogen and a yet unknown Pythium species closely related to P. phragmitis and P. arrhenomanes. Internal tran...
Pythium species are economically significant soilborne plant pathogens with worldwide distribution, causing seedling damping-off or root rot diseases. Pythium phragmitis is a newly described pathogen of common reed (Phragmites australis), widespread in the reed-belt of Lake Constance, Germany. It is highly aggressive towards reed leaves and seedlin...
Coinciding with a population decline in the invasive spiny-cheek crayfish Orconectes limosus in Lake Constance, SW Germany, we found crayfish specimens with a fungus-like Aufwuchs which after DNA-isolation and sequencing was identified as consisting of a set of previously undescribed Saprolegnia species. This finding may have implications for the f...
We studied the diversity of oomycetes in a declining reed belt (Phragmites australis) of Lake Constance, Germany, using conventional baiting with specific reed and standard oak baits, accompanied by molecular techniques. Apart from an Aphanomyces sp. and a Phytophthora sp., baiting from reed rhizosphere samples from flooded, as well as drier, litto...
Cotoneaster nebrodensis, die Filzige Zwergmispel, ist ein 1-3 m hoher, sommergrüner, unbewehrter Strauch von ästig-aufrechtem Wuchs, der in Gebirgsregionen des südlichen Mittel- sowie Südeuropas beheimatet ist. Die allgemein nur selten bis zerstreut vorkommende Art ist der Gemeinen Zwergmispel (C. integerrimus), mit der sie sich Teile des Verbreitu...
A non-papillate, slow-growing Phytophthora species, which could not be assigned to any existing taxon, was isolated from rhizosphere soil of a declining oak in Northeast France, and from the rhizosphere of Phragmites australis at Lake Constance in south-west Germany in 1998 and 2004, respectively. We describe this species, previously informally des...
An unnamed ITS clade 6 Phytophthora was frequently isolated from rhizosphere soil of reed (Phragmites australis) growing on the littoral zone of Lake Constance. The isolates closely resembled P. gonapodyides, having internally proliferating, non-papillate sporangia, a rather high temperature optimum for growth (30 C), and being sexually sterile. IT...
A description is given of Pythium litorale sp. nov., a new species from reed stands in Germany. Pythium litorale was among the most abundant species when the oomycete community of littoral soils of Lake Constance was studied. It was consistently isolated from flooded as well as from drier reed sites. The species is characterized by subglobose, papi...
During a study on the occurrence and pathogenicity of oomycetes in the reed-belt (Phragmites australis) of Lake Constance (Germany), a new Pythium resembling the important cereal pathogen species complex P. arrhenomanes/P. graminicola was consistently isolated from necrotic mature reed leaves and reed rhizosphere samples. The new species proved to...
On Apr 25, 2005 this sequence version replaced gi:61657700.
On Aug 14, 2007 this sequence version replaced gi:47059603.
Cotoneaster integerrimus ist ein bis etwa 2 m hoher, sommergrüner, relativ seltener Strauch Europas und Südwestasiens von aufrecht-sparrigem bis niederliegendem Wuchs. Als wärmeliebende Art mit Pioniercharakter kommt die Gemeine Zwergmispel bevorzugt in lichten Wäldern und Gebüschen auf trockenen, felsigen Standorten vor. Ihre unscheinbaren, nektar...
The genus Phytophthora (Greek “plant destroyer”) includes many soilborne species which cause root and collar rot symptoms of herbaceous and woody plants including different forest trees. This review will focus on Phytophthora diseases of forest trees, as their significance has increased in recent years. Chlorosis, necrosis and wilt symptoms can be...
In several studies of oak decline in Europe, a semi-papillate homothallic Phytophthora taxon was consistently isolated, together with other Phytophthora species, from rhizosphere soil samples. It was also found associated with necrotic fine roots and stem necroses of Fagus sylvatica and Alnus glutinosa. Due to morphological and physiological simila...
Extensive investigations on the fine root status of declining and healthy spruce were conducted in several stands at higher elevations of the Bavarian Forest heavily affected by needle yellowing. In most of the root parameters recorded, yellowing trees had significantly lower values than neighbouring green trees. Tight correlations were found betwe...
Die Felsenbirne ist ein bis etwa 3 m hoher, sommergrüner Strauch, der in den Gebirgsregionen Europas, Kleinasiens und Nordafrikas heimisch ist. Die wärmeliebende Art kommt hauptsächlich in lichten, südexponierten Wäldern und Gebüschen auf kalkreichem Untergrund vor. Sie kann als Pionierart z.T. extreme Standorte besiedeln. Die zahlreichen weißen Bl...
During a study on soilborne Pythiaceae in the Bavarian Alps, 3 isolates of a papillate Pythium species with aplerotic oospores were found in rhizosphere soil from a declining spruce stand. The isolates showed a unique
combination of sporangial and gametangial characters, and could not be assigned to any known species of the genus. They were
charact...
Investigations on root and crown status of spruce and beech were carried out on selected trees in the ‘Werdenfelser Land’ area (Bavarian Alps, Southern Germany). In addition, the association of fine root pathogens of the genera Phytophthora and Pythium with the trees’ rhizosphere was studied. In a variety of stands representing various site conditi...
A description is given of the use of a combination of polymerase chain reaction (PCR) and baiting techniques for the specific detection of Phytophthora quercina and Phytophthora citricola from soil around declining oak trees. The soil was flooded with water and subjected to a specific baiting procedure using Quercus robur leaflets as baits. Single...
Specific primers and dual-labelled fluorogenic probes were designed for polymerase chain reaction (PCR)based detection of both, mycorrhizal and pathogen DNA. Based on the on-line connection with an automated ABI Prism 7700 sequence detector, amplicon quantification was directly performed during the PCR. The starting copy numbers of target sequences...
Oligonucleotide primers were developed for the polymerase chain reaction (PCR)-based detection of selected Phytophthora species which are known to cause root-rot diseases in European forest trees. The primer pair CITR1/CITR2, complementing both internal transcribed spacer regions of the ribosomal RNA genes, gave a 711 bp amplicon with Phytophthora...
Questions
Questions (5)
In our phytobacteriology lab, there is a general rule that bacterial cultures (single colonies) must not be subcultured consecutively from one selective agar medium (i.e. media containing antibiotics) onto another selective agar medium. We currently cannot figure out an original source for this rule, so do not know if this is generally “correct” or advisable, and if so: why? Does anyone have an idea? Thanks!
We are using the Voges-Proskauer test to differentiate plant pathogenic Enterobacteria (we are using the Rosco Diatab system). Most protocols recommend incubating the cultures at 35-37°C for 48h to produce a dense suspension for the test. Diatabs also recommends incubating at 35-37°C before Barritt’s Reagents A and B are added. I wonder whether the temperature recommendation is because many Enterobacteria are from clinical samples (and so this is likely their optimum growth temperature), or this temperature is needed for the test itself. In other words: do we need to incubate Pectobacterium/ Erwinia etc. at 35-37°C, or at their optimum growth temperature which is of course much lower?
The fruit has about the size of a medium-sized apple. The small tree grew in the botanical garden of Funchal, Madeira, but unfortunately had no label. The seed had already germinated inside the fruit.
