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In the years 1995-2004 the spectra of weeds, diseases and pests in grasses grown for seed in the Czech Republic were examined and the effect of external factors on their changes was assessed. The species spectrum of weeds evaluated both at the time of vegetation and in samples of natural seeds was stable throughout the period and the changes in the number of individual species were caused by different proportions of grass species and stand age. The most abundant weeds were Elytrigia repens, Matricaria sp.div., Anthemis sp.div., Apera spica-venti, Cirsium arvense, Poa trivialis, Rumex sp.div. and Chenopodium sp.div. The most serious diseases were parasitic silvertop, graminicolous rusts (Puccinia sp.div.), Blumeria graminis and ergot (Claviceps purpurea). The rate of rust occurrence was affected by climatic conditions; the spectrum of other diseases was stable throughout this period. The most important animal pests were Muridae rodents.

During 4 years, 27 cultivars and breeding lines of winter wheat (Triticum aestivum) were tested in small plot experiments for resistance to powdery mildew fungus. The most resistant were Frimegu, RE9607, Runal, Asset, Folke and Wasmo. The cultivars Asta (Pm2,6) and Vlasta (Pm2,6 and another not determined specific gene or minor genes of resistance) fall into resistant cultivars. It seems that the specific genes of resistance Pm2 and Pm6 are still very effective against the present Czech population of powdery mildew on wheat. Resistance of the cultivars Hereward and Tarso, having the gene of resistance Pm8, can be ascribed to an additional undetermined gene that is effective only in mature plants. The cultivars Mikon and Ramiro with partial resistance had a higher infection type and disease severity than resistant cultivars, but lower disease severity than the susceptible cultivar Kanzler.

Cultivars, homozygous sources and lines of pea (Pisum sativum L.) resistant to Erysiphe pisi had recently been attacked by another powdery mildew species, Erysiphe baeumleri, in the field and in glasshouse conditions. Inoculation with E. baeumleri was carried out in the glasshouse to evaluate the level of resistance of 16 pea genotypes. Susceptible pea lines produced abundant conidia and cleistocarps on petioles and leaves. Only the genotype Tudor (Cebeco 4119) was found to be completely resistant to E. baeumleri. Nineteen pea genotypes (with gene er-1) were tested to natural infection by E. baeumleri in field screening trials. Only few of them demonstrated a high level of resistance (Fallon, AC Melfort and Joel). Consort R, SGL 2024, SGL 1977 and Franklin were very susceptible to E. baeumleri. Cleistocarps with 1-4× dichotomously branching apices of appendages were formed only on susceptible and very susceptible plants of genotypes SGL 444/2185, Consort R, SGL 2024, SGL 1977, LU 390-R2, Lifter, Highlight, Cebeco 1171 and Carneval R in the field and glasshouse. Susceptible control genotypes without gene er-1 (Komet, Adept and Gotik) were attacked in the trials by E. pisi only.

In 1995-1997, the population dynamics of the flea beetles Chaetocnema tibialis and Phyllotreta vittula, associated with Amaranthus retroflexus (wild species) and Amaranthus caudatus (cultivated species), were studied at the locality Nitra-Malanta (48°19'N, 18°09'E) in south-western Slovakia. On both plant species, the number of C. tibialis adults was usually very low until the beginning of July. During July the number of C. tibialis increased, but sooner on cultivated amaranth. An increased number of C. tibialis adults was observed on both amaranth species until the middle of September. The results showed that amaranth plants are a very important reservoir of C. tibialis during summer. P. vittula was a common flea beetle on amaranth during the whole summer, but its numbers never exceeded more than 10 adults per 25 plants. Low temperatures in winter had a negative effect on populations of C. tibialis on both amaranth species and also on populations of P. vittula on A. retroflexus. The lower the precipitation was in July, the higher were the populations of C. tibialis on both amaranth species and the populations of P. vittula on A. retroflexus.

Hop downy mildew (Pseudoperonospora humuli) and hop powdery mildew (Podosphaera macularis) are the most important pathogens of hop (Humulus lupulus). The early detection and identification of these pathogens are often made difficult by symptomless or combined infection with another pathogens. Molecular analysis of internal transcribed spacer (ITS) regions of rDNA is a novel and very effective method of species determination. Therefore, specific PCR assays were developed to detect the pathogens Pseudoperonospora humuli and Podosphaera macularis in naturally infected hop plants. The specific PCR primer combinations P1 + P2 and S1 + S2 amplified specific fragments from Pseudoperonospora humuli and Podosphaera macularis, respectively, and did not cross-react with hop DNA nor with DNA from other fungi. PCR primer combinations R1 + R2 and R3 + R4 could be used in multiplex PCR detection of Pseudoperonospora humuli, Podosphaera macularis, Verticillium albo-atrum and Fusarium sambucinum. Phylogenetic relationships were inferred for 42 species of the Erysiphales from nuclear rDNA (ITS1, 5.8S, ITS2). The molecular characterisation and phylogenetic analyses confirmed the species identification of hop powdery mildew. The PCR assays used in this study proved to be accurate and sensitive for detection, identification, classification and disease-monitoring of the major hop pathogens.

Population studies and tests on the relationship between density and damage were conducted in 1999 to 2001 to determine the pest status of Empoasca dolichi on groundnut (Arachis hypogaea L.) in the Zaria area of northern Nigeria. Analyses showed that Empoasca numbers varied significantly from one year to another, and within each year the numbers of leafhoppers observed at the different growth stages of the plant were significantly different (P = 0.01). There was an inverse and highly significant relationship between the mean kernel yield and the Empoasca damage at the different growth stages of the plant. When natural population densities were plotted against economic injury level (EIL), the densities did not reach the EIL throughout the groundnut growing seasons. The insect was thus not an economic pest on groundnut in Zaria during the period of the study.

The bacterium Pseudomonas savastanoi pv. nerii was identified as the causal agent of parenchymatous galls on leaves of potted oleander plants grown at Brno, Moravia, in 2004. The plants had originated from cuttings made from firm shoots of a supposedly asymptomatic plant grown in and introduced from the Mediterranean region. The Biolog GN microplate system was used to identify the isolated bacterial strains. Successful inoculation of Nerium oleander seedlings proved the pathogenicity of the isolates. This is the first record of P. savastanoi pv. nerii in the Czech Republic. :

The mortality of pupae in stems lying on the ground during hibernation was 51.7% in 2003. The emergence of adults in 2003 and 2004 was monitored from late April to early July by photoeclectors placed on fields that grew poppy the previous year. Most adult gall wasps emerged in April to early May 2004. The occurrence of females ovipositing on poppy stems varied from April to July and the degree of damage to the plants increased. Most frequently the females oviposited in the first stem internodes. The infestation of poppy cultures with the gall wasps was almost uniform, the number of infested plants increasing still in June. In late June, only seven out of 600 plants were not infested. Green sticks covered with non-coagulating glue and placed in the poppy field, indicated the stem heights frequented by ovipositing females. The gall wasp larvae were parasitised by Trichomalus bracteatus Walker and Pseudotorymus papaveris Ruschka, with T. bracteatus predominating. Most frequently, gall wasp larvae inside the seventh internode were parasitised by this species.

The species composition, frequency and abundance of insect pests (Coleoptera) occurring outside a grain store were explored. Wheat bait traps were used for pest monitoring; they were changed every month from April to September. For the first time the outdoor occurrence of primary and secondary stored-product pests was documented in the Czech Republic. Seven species of Coleoptera were found outside the grain store. Pest abundance and frequency were in high correlation. The primary pest Sitophilus granarius was dominant.

The response of 25 registered winter wheat varieties to autumnal infection with Wheat dwarf virus (WDV) was studied in small plot trials in two years. The materials were infected by vectors, leafhopper Psammotettix alienus Dahlbom, 1851 from three-leaf stage to tillering. The symptoms expression was monitored in spring and plant height, weight of above ground biomass and grain yield were observed in summer. All tested varieties were evaluated as susceptible and divided into three groups: varieties Banquet and Svitava with 87.3-93.1% grain yield reduction as moderately susceptible, varieties Clever, Drifter, Niagara and Rialto with 95.6-97.68% grain yield reduction as susceptible and varieties Apache, Batis, Bill, Complet, Contra, Corsaire, Ludwig, Mladka, Nela, Record, Rheia, Semper, Sepstra, Solara, Sulamit, Tower, Trend, Vlasta and Winsdor with 99.7-100% grain yield reduction as very susceptible. Statistically significant differences were observed between moderately susceptible and susceptible varieties as well as very susceptible ones in absorbency values by means of DAS-ELISA.

An unusual disorder occurred on spring barley seedlings in southern and central Bohemia in April 2005. Affected seedlings showed conspicuous bleached or straw-coloured areas on tips of the first leaves. There were very sharp, distinct, horizontal boundaries between the green basal and discoloured tip parts of the leaves. It was remarkable that these boundaries were at the same position on all affected first leaves of seedlings from the same field. Affected seedlings were randomly distributed in the fields, and their incidence ranged from about 20 to 70% according to location. Based on meteorological data it can be concluded that the colour abnormality in emerging seedlings was associated with specific environmental stresses, being effective in certain chronological order on sensitive plant tissues during the period from 6 to 8 days after seeding. These stresses include frosty mornings followed by clear days with high solar radiation with a high UV Index.

In 1997-1998 virulence of the wheat leaf rust population was studied on Thatcher near isogenic lines with Lr1, Lr2a, Lr2b, Lr2c, Lr3. Lr9, Lrll, Lrl5, Lrl7, Lrl9, Lr21, Lr23, Lr24, Lr26 and Lr28. On these NILs 11 pathotypes were determined in 1997, and 8 inl998. All rust samples were avirulent onLr9, Lr19, Lr24 and Lr28.There was a relatively low frequency of virulence on Lrl, Lr2a and Lr2b. Most rust samples were virulent on Lr2c, Lr11, Lr15, Lr17, Lr23 and Lr26. All samples were virulent on Lr3 and Lr21. The identified pathotypes conformed with races 61SaBa*, 77SaBa, 2SaBa, 12SaBa, 57SaBa, 6SaBa, 61*, 77 and 6. Races 61SaBa*, 77SaBa and 2SaBa prevailed in 1997, races 61 SaBa*, 77SaBa and 12SaBa were prevalent in 1998. Races 6 and 6SaBa were found for the first time. Data on Lr genes in recently registered winter wheat cultivars are presented.

Viruses as phytopathogenes have been discovered at 1892, and 638 plant's viruses have been identified at 1989. Some of its may be epidemic and to cause significant yield losses of cultivated crops. Increasing resistance of the single plant and populations is the necessary condition for the control of viruses spread and damage. Our proposals for the increasing resistance to viruses: For the single plant the soft correction of plant's metabolism with pretreatment of the natural bioantioxidants and immunizators - steroid glycosides. It results in lowering of virus infectivity, degree of plant's affection and increasing of the yield on 11-41% in fact (in ToMV-tomato pathosystem). For the plant's population- increasing to the necessary proportion the lot of tolerant and resistant forms into the plant's assortment; - selection of resistant and tolerant forms from populations have been selected earlier as resistant to other pathogens and obtaining of the basic material collection with complex resistance; - hybridization programs and developing of tolerant and resistant hybrids; - use molecular markers of resistance for the limitation of virus infection backgrounds in the breeding programs.

We determined partial nucleotide sequences of several different field isolates of PMTV with well-characterized biological properties from the Czech Republic and Denmark. Subsequently we were trying to elucidate the correlation between nucleotide sequences of various isolates, their biological properties and geographical origin. From the comparison with other known sequences we can conclude, that PMTV genome is relatively conserved.

In 1998 and 1999 a total of 84 samples of corn, predominantly from localities in southern and central Moravia, were collected either directly from fields (entire ears at harvest maturity) or as grain from merchants. The objectives of the experiments were (a) to determine, on the basis of the results from mycological and toxicological analyses, the basic spectrum of fungal contaminants of corn in the Czech Republic with special reference to the genus Fusarium, and (b) to determine by enzyme immunoassay the presence of major toxic metabolites such as deoxynivalenol (DON), T-2 toxin (T-2), zearalenone (ZEA), and fumonisins (FUM) in grain samples. From naturally infected corn, representatives of seven fungal genera were isolated under in vitro conditions in both harvest years. Most frequent were species of the genus Fusarium (mean contamination of 44.6%). The next frequent genus was Stemphylium (29.3%). Eight species of Fusarium were found. In both years the most frequent species was Fusarium graminearum (1998 - 42.75%, 1999 - 41.8%), followed by F. culmorum. DON was found in 95.2% of the samples; its content ranged from 25 to 285 µg/kg. The content of T-2 varied more than that of DON, ranging from 12 to 875 µg/kg. Zearalenone content was more varied than that of the trichothecene-type compounds; 17% of the samples did not contain ZEA, the maximum content was 110 µg/kg. No FUM were found in 17% of the samples; in the others, FUM ranged from 12 to nearly 1000 µg/kg. Compared with the other three compounds, fumonisins showed generally the highest levels.

The objective of the study was to identify genes for resistance to powdery mildew in wheat cultivars and land races from Poland, Slovakia and Hungary. The presence and distribution of resistance genes was compared to powdery mildew virulence structure in these countries. The different strategies in breeding for resistance were expressed in a different distribution of resistance genes, especially among Polish and Hungarian cultivars. In 20 of the 29 Hungarian common wheat cultivars the resistance gene Pm8 was found. Of the 32 Polish cultivars investigated, 16 possess a combination of genes Pm2+6. Resistance gene Pm4b did not occur in any Hungarian cultivar tested, and resistance gene pm5 was not detected in any Polish cultivar. Virulence in wheat powdery mildew populations was influenced by differences in distribution of resistance genes in host genotypes. The most significant difference was found between Polish and Hungarian powdery mildew populations. The two populations differed mainly in virulence against Pm2. Resistance gene MlAr was detected in three old Slovak cultivars.

The resistance of six cultivars of winter oilseed rape (SL 509, SL 507, Darmor, Solida, Jet Neuf, Silesia) against Turnip yellow mosaic virus was studied. The number of over-wintering plants and plants with symptoms of TYMV infection were monitored. All plants were tested by the double diffusion test in agar and by DAS-ELISA to prove infection. ELISA was the most sensitive method, revealing 32-76% of latent virus infections in individual cultivars. The results clearly illustrated that monitoring of plant symptoms is not sufficient to prove TYMV infection in the field and that sensitive, large scale methods like ELISA must be employed to obtain reliable data.

Field resistance can contribute to reductions in epidemic progress of Septoria tritici in winter wheat. Crop growth andcanopy architecture are identified as key mechanisms of field resistance. Near isogenic lines differing for dwarfing (Rht)and photoperiod sensitivity (Ppd) genes, enabled the study of target traits in a constant background of genetic resistance.Epidemics were consistently earlier in shorter crops across a range of environments. The mechanism for this effect wasidentified as an increase in spore arrival due to a reduction in the required dispersal distance between infective tissueand emerging upper culm leaves.

In 1999-2001 in field trials two different apple scab control strategies were compared: (i) the current strategy - conventional disease management (CDM) and (ii) integrated disease management (IDM), according to scab infection periods. A new scab warning equipment METOS^R-D was used for detection of infection periods and forecast of disease intensity at three levels: light, moderate and severe. According to CDM apple-trees were sprayed 9 times a season. Scab warning equipment gave a possibility to optimize the use of fungicides against scab and to reduce the total spray applications per season in average till 6.3 in very susceptible cultivars and 5 in moderately susceptible ones. This is 30 and 44% less spray applications comparing with CDM. Annual spray program ranged from 5 till 8 spray applications of very susceptible cultivars. CDM and IDM gave high scab control in apple-trees and there was not found any essential difference in scab incidence between two control strategies.

Ergot, caused by the fungus Claviceps purpurea (Fr.) Tul., belongs to the main constraints in seed production of Kentucky bluegrass (Poa pratensis L.). The level of ergot occurrence depends on the weather conditions during the growing period, harvest year, storage conditions of seed, and post-harvest treatment. The degree of resistance of the grown cultivar plays an important role. Based on greenhouse trials with four different ergot populations (Zubří, Czech Republic; Leutewitz and Munich, Germany; Pullman, Washington, USA) during 3 years, we found pathogenicity to be one of the most important factors. There were significant differences in the amount of ergot bodies formed between the Central European populations (Zubří, Leutewitz) and the American one from Washington State. The degree of pathogenicity has a major impact on the occurrence of ergot sclerotia in seed of Poa pratensis.

Wheat dwarf virus, a monogemini virus, infects several cereal species. Until now complete sequence data have been published only for wheat isolates. We cloned the complete DNA of 21 isolates from wheat, barley and Lolium spec. and compared the sequences with published data. Two types of the virus were found as previously described. Degree of entire nucleic acid homology between both isolates was in the range of 84%. The Large Intergenic Region showed most pronounced differences while the RepA gene was most conserved. No intermediate forms were found, though both isolates co-existed in the same hosts. Sequence data lead to the suggestion that they should be referred to as different viruses rather than strains of a virus.

In 1999-2001 the investigation of Alternaria species on vegetable crops: cabbage, cucumber, tomato and carrot was carried out and fungi species were isolated from vegetables and substrata used for plant cultivation. Isolated micromycetes: Alternaria alternata, Alternaria tenuissima, Alternaria brassicae, Alternaria brassicicola, Alternaria cucurbitae, Alternaria dauci, Alternaria radicina and Alternaria solani differed in pathogenic peculiarities, frequency of occurrence and their various reaction to fungicides (a.s. azoxystrobin, dichlofluanid, Cooper hydroxide, mancozeb, propamocarb hydrochloride), plant activator Bion (benzothadiazole) and antagonistic microorganisms (Trichoderma harzianum, Streptomyces griseoviridis).

The trials were carried out over the period 1999-2000 with a view to testing the efficacy of reduced doses of triazole fungicides on winter wheat cv. Zentos. Septoria diseases (Septoria spp.) occurred on winter wheat annually. Full and reduced dosages of fungicides were highly effective against Septoria leaf blotch at an early milk stage, especially on flag leaf. Later the efficacy of reduced dosages of the fungicides was lower, than that of full doses. Due to full dosage of fungicides we obtained a sufficient yield increase annually. The yield increase through the use of 3/4 reduced doses was lower. But yield increase through reduced dosage to 1/2 was low and insufficient.

During 1996-2000 the secondary succession on a field left fallow was investigated. The experimental area was divided into a ploughed and an unploughed part. Both parts were divided into 5 × 5 m plots that were either left intact (control), mowed in June or July, or superficially cultivated in June. The position of the plots was identical each year. In successive years total dry matter production decreased in all experimental plots; in unploughed plots more than in ploughed ones. The spread of Cirsium arvense (L.) Scop. was increased by ploughing and superficial cultivation. Ploughing stimulated the spread of perennial dicotyledonous plants more than mowing in June and July. Superficial cultivation increased the spread of perennial dicotyledonous plants in the first years. Later on the proportion of perennial dicotyledonous plants decreased and after 5 years the plots were dominated by Anisantha sterilis (L.) Nevski. The incidence of Elytrigia repens (L.) Desv. was highest in the 5th year on unploughed control plots. The spread of perennial monocotyledonous plants was lowest in ploughed and superficially cultivated plots.

ocids are commonly found to be a persistent pest in structures of grain stores. Grain residues are potential pest reservoirs that serve as sources of grain re-infestation. Weight losses caused by psocids on broken wheat kernels were measured. Average weight loss of grain samples was 9.7% after 3 months of Liposcelis bostrychophila infestation. The weight losses were positively correlated with progeny production.

Results of researches carried out in 2000 and 2001 have demonstrated, that main factors determining yield of winterwheat are: agrotechnical measures, mainly proper choice of field, optimal nitrogen fertilization as well as choice ofcultivar well adapted to local climatic conditions. Chemical protection of winter wheat affects first of all stability ofyield. Regular inspections of fields with special account to present phytosanitary situation, thresholds of noxiousness andexpected development of disease and pest populations should decide on the need of chemical treatments.

The tolerance to or phytotoxicity of selected herbicides and their impact on seed yield was investigated in six grasses grown for seed: Phleum pratense cv. Sobol (a), Festuca rubra cv. Táborská (b), Festuca pratensis cv. Otava (c), Poa pratensis cv. Slezanka (d), Arrhenatherum elatius cv. Medián (e) and Dactylis glomerata cv. Zora (f). All species were tolerant to Grodyl 75 WG (amidosulfuron 75%), (a) and (f) were tolerant to Grodyl plus (amidosulfuron 15 g/kg + isoproturon 600 g/kg) which was phytotoxic to the other grass species; all species were tolerant to Stomp 330 E (pendimethalin 330 g/l); Lintur 70 WG (triasulfuron 4.1% + dicamba 65.9%) was phytotoxic only to (c) while the other species were tolerant to it.

First outbreaks of fire blight were detected in Austria in 1993 and in Hungary in 1995. 137 Erwinia amylovora isolates were compared by PCR-RFLP, sequencing of the repeat region of the PstI fragment of plasmid pEA29, RAPD and AFLP analysis. Differences of repeat numbers in first isolates were observed. Six isolates showed different RAPD profiles. In AFLP analysis, so far, no differences in fragment pattern were determined. Pathogenicity tests with micropropagated apple cultivars revealed differences in plant susceptibility and in virulence of isolates. Responses of Malus tissue were visualized by the use of epifluorescence microscopy through the localization and the production of substances involved in cellular defence mechanisms (e.g. flavonoids, lignin) in various susceptible cultivars. The effect of bacterial strains differing in pathogenicity is shown by cellular peroxidase and flavonoid production.

Leaf spot pathogen is characterized as a highly developed parasite after investigation of development peculiarities of the fungus in pure culture and natural conditions. The degree of correlation depended on the medium. Impact of incubation temperature on Blumeriella jaapii (Rehm) Arx growth was different. Fungi colonies formed more intensively and their diameter increased significantly under higher temperature. Optimal conditions for the disease prevalence are 15-20°C and moisture. Relative humidity and precipitation influenced maturation of ascomycetes and discharge of ascospores (r = +0.89). Microscopic analysis of leaves showed that during winter thaw, when the average temperature is about 0 ± 5°C and relative humidity is higher than 70%, was possible to detect mature ascomycetes and conidia. It is possible to affirm that lower temperature than it was assumed is sufficient for formation of ascomycetes.