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With regret, we have to inform the community of plant pathologists, plant virologists, and plant protection scientists. Assoc. Prof. Jaroslav Polák, a former and long-time Plant Protection Science editorial board member, passed away on May 20, 2024.

In 2024, the journal Plant Protection Science (PPS) completes 60 years of publication (1965-2024). Its roots extend back to the year 1921. In recent years, PPS has developed into an international scientific journal focused on all aspects of plant protection science, published exclusively in English, and with an international editorial board. The publisher is the Czech Academy of Agricultural Sciences (CAAS), celebrating its 100th anniversary (1924-2024). PPS is one of eleven agricultural journals published by CAAS. On its 50th anniversary, PPS published a detailed overview of its history and development. This latest critical review summarises developments during the last ten years; however, in special cases, also with a longer-term perspective. During the last decade, PPS has made impressive progress and is now among the world's key scientific journals. Recently, the journal has been added to the indexing and abstracts of many international databases, e.g. BIOSIS Previews, SCOPUS and Web of Science. In 2014, PPS had an impact factor of 0.597, but during the last few years, PPS's IF has ranged between 1.3 and 1.4 (for 2023, IF = 1.7), with the possibility of further increase. Each year, PPS is published quarterly, with a total of around 40 papers (original papers, reviews, short communications, biographical notices, and book reviews). Per year, about 70-80% of papers by authors/co-authors from abroad are published (Europe, America, Asia, Australia and Oceania). In the final part of this presentation, we describe some recent achievements and discuss key topics related to PPS's future development.

Brassica and related crops are one of the most important and widely growing crops around the world. They have very broad utilization in human activities as fresh and processed food, fodder and forage of animals, condiments and ornamental plants. This group of plants belongs to one of the oldest domesticated crops with very wide geographic distribution and history of growing and human utilization. Brassicas are also very diverse from taxonomical and genetic viewpoint with rather long history of breeding. The First Edition of this book was published by CABI in 2006, this volume received very high evaluation and by reviewers was considered as "an exemplary job in making horticultural sense". However, during the last two decades there was made enormous progress in research, breeding, growing and practical aspects of utilization of these crops. This newest edition of the book represents a very impressive, comprehensive and complex treatment of all the most important aspects related to vegetable brassicas and related crucifers used in horticulture.

This article focuses on the occurrence of powdery mildews in the Lamiaceae family in the Czech Republic. A comprehensive analysis of morphological characteristics supported by molecular analysis of partial ITS sequences and analysis of host species gained important insights regarding the occurrence and diversity of powdery mildews. Thirty-four plant samples of the Lamiaceae family infected by powdery mildew collected in the Czech Republic between 2015-2022 were analysed. In these samples, the occurrence of all newly described species within the former Golovinomyces biocellatus complex was confirmed (G. biocellatus, G. salviae, G. neosalviae and G. monardae), and Neoërysiphe galeopsidis was also verified. Moreover, our study expands the already reported host species list of G. biocellatus complex within the Lamiaceae family.

On February 23, 2022, the great Czech plant pathologist, and my personal friend and esteemed colleague, prof. Václav Kůdela passed away. For over 15 years (1990-2006), he served as the Editor-in-Chief for our journal, Plant Protection Science. His whole adult life was connected with agriculture, plant pathology, plant protection and the science of phytotherapy. However, he was also man who accepted, maintained, applied and lived his life following specific, serious traditional rules. The trajectory of his life and its fundamental message arose primarily from his family origins and experiences in youth.

Powdery mildews on the Asteraceae family were surveyed during 2007-2015 in the Czech Republic with the aim to increase our knowledge about occurrence, morphological characteristics and host specificity of powdery mildews on this family. In total, 32 host species with symptoms of powdery mildew were collected, and the fungal species were identified based on microscopic observations. These showed great variability in their morphological characteristics. Our study confirmed the high host specificity of powdery mildew species to their original hosts. A deeper knowledge of the taxonomy of the Asteraceae has brought substantial changes in the delimitation of powdery mildew species. In particular, delimitation of the three varieties of Golovinomyces asterum was studied and discussed.

The effect of plant heat-shock (HS) pre-treatment (40.5°C, 2 h) on Pseudoidium neolycopersici development in the susceptible and moderately resistant Solanum spp. genotypes was studied together with biochemical responses (endogenous concentrations of salicylic (SA), jasmonic (JA), abscisic acid (ABA), and peroxidase (POX) activity). In HS pre-treated S. lycopersicum, an acceleration of pathogen, chlorosis and necrosis development, strong SA, JA accumulation, and increased POX activity were detected. In S. chmielewskii, HS pre-treatment caused a slight suppression of pathogen development, increase in JA, ABA concentrations, and POX activity. HS accelerated and strengthened the development of symptoms and biochemical responses to the infection in the susceptible genotype in contrast to moderately resistant genotype with a robust defence response to an infection per se.

Prof. Ing. Karel Veverka, DrSc. was an important figure in Czech agricultural phytopathology at the turn of the 20th and 21st centuries. His long, diverse experiences in the field of plant protection, combined with his excellent public speaking skills, led him to be recognized as one of the erudite experts of his time. His skillful presentations were widely appreciated at scientific conferences and seminars and at university lectures for students. All his scientific life, he kept contacts in the broader world of agricultural production, to which he was very close due to his personal experience. His expertise in chemical plant-protection products was unsurpassed. Beyond his own research and teaching activities, he always found time for the popularization of science. He published his achievements in both scientific journals and the popular-scientific press, being the author of numerous publications on plant protection, pesticides, the spread of fungal pathogens, diagnostics, and monitoring and epidemiology of phytopathogenic fungi.

Polyploidy in sturgeons makes them highly susceptible to interspecific hybridization, and these interspecific hybrids have been described in nature as well as in captivity. Nevertheless, the fitness-related traits between sturgeon hybrids and pure species have been poorly compared as yet. In the present study, we compared the reproductive parameters such as fertilization rate and hatching rate, growth traits and genetic polymorphism in the artificially produced hybrids of the Siberian sturgeon (Acipenser baerii) and Russian sturgeon (A. gueldenstaedtii) with their purebreds. Fertilization and hatching rates were found to be significantly higher in Siberian sturgeon (♀) × Russian sturgeon (♂) hybrid group compared to purebreds. The highest cumulative survival rate was determined in purebred groups until 151 days post-hatch (dph); however, this trend changed and Russian sturgeon purebred showed the lowest cumulative survival rate (0.21%) by 913 dph. Similarly, the lowest average body weight was recorded in Russian sturgeon purebred group (264 g). In contrast, the highest average body weight was recorded in Russian sturgeon (♀) × Siberian sturgeon (♂) hybrids (435.3 g) and the highest cumulative survival rate was recorded in Siberian sturgeon (♀) × Russian sturgeon (♂) hybrids (12.32%) by 913 dph. No significant differences were found at heterozygosity levels among studied crosses. Our results showed that studied sturgeon hybrids had higher survival and growth if compared with the purebreds under provided hatchery conditions.

Downy mildew caused by Plasmopara halstedii significantly reduces annual yields of sunflower. At least 42 races of P. halstedii have been identified around the world. For the first time to our knowledge, races 705 and 715 of P. halstedii have been isolated, originating from sunflower plants collected at a single site (Podivín, South-East Moravia) in the Czech Republic at the beginning of June 2014. This enlarges the global number of the so far identified and reported races of P. halstedii to 44. The increasing complexity of P. halstedii pathogenicity led to race identification newly by a five-digit code. According to this new nomenclature, the two races of P. halstedii recorded in the Czech Republic are characterised by virulence profiles 705 71 and 715 71.

Four broodstocks of European huchen (Hucho hucho) from Poland, Germany, Slovakia, and Ukraine were investigated using five selected fragments of mtDNA. The mitochondrial DNA sequence analysis was successfully applied to the Polish and German broodstocks of European huchen for the first time. A very low haplotype (h = 0.097) and nucleotide (π = 0.00013) diversity across 3573 bases of mtDNA fragments (partial regions of NADH-1, NADH-5, ATPase 6, Cytochrome b, and D-loop) evidenced by three closely related mtDNA haplotypes were found. The analysis of pairwise genetic differentiation (Fst) displayed a statistically significant differentiation between German (clade A) and the rest of examined broodstocks (clade B), clustering them into two separate groups. Moreover, the applied mtDNA markers did not reveal any differences among fish from the clade B, suggesting that other markers should be used to display a deeper genetic background of the studied broodstocks. The two clusters of European huchen distinguished under the current study should be considered as distinct management units by managers, who may be tempted to transport brood fish or yearlings across the range of European huchen distribution. It means that stocking material and spawners of European huchen from the upper parts of the Danube River (Clade A) should not be mixed with those from the lower parts (Clade B). Moreover, for any supplementation of broodstocks in order to increase their genetic variability only the fishes within the described management units should be used.

A field survey was carried out in cucumber plantations from different localities in Mauritius to identify the causal pathogen and assess incidence of oily spots on cucumber fruits cv. Locale. ELISA tests on symptomatic fruits showed the presence of CMV and ZYMV. The viruses from the genus Potyvirus PRSV and WMV-2 were not detected in the samples screened. Three types of symptoms were observed on infected cucumber fruits: distortion; distortion with oily spots, and oily spots. CMV was detected on fruits showing distortion with oily spots and those with oily spots only. ZYMV was detected in all fruits with distortion and not in those with oily spots only. The above findings showed that oily spots on fruits are caused by infection with CMV. Mechanical transmission of CMV from the oily spotted cucumber fruits to young cucumber cv. Locale plants clearly indicate the association of CMV infection with the oily spot symptoms.

Chromosomal manipulations in sturgeons, particularly gynogenesis, are interesting due to the potential to change female ratio in progeny that can be useful for caviar production. The optimization of UV treatment for induction of gynogenesis is complicated due to high and variable optical density of the milt due to differential spermatozoa concentration, and because of sensitivity of spermatozoa's motility apparatus. Therefore in this study we compared chemical methods of sperm treatment as an alternative to short wave-length UV treatment; evaluation considers impact on spermatozoa motility, DNA integrity, and efficiency of DNA inactivation. Dimethyl sulfate (DMS) in concentrations of 2.5-30mM was applied to spermatozoa in order to inactivate DNA. Also ethidium bromide (EB), psoralen (PS), and 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT) were used to increase sensitivity of spermatozoa's DNA to long wavelength UV-A light (360 nm). CASA analyses of treated sperm showed strong negative effects on spermatozoa motility with the increasing concentration of active substances. Additionally in case of PS, EB, and DMS treatment comet assay did not reveal significant DNA damage of sperm at the range of concentrations relatively safe for spermatozoa motility. Flow cytometric analysis of relative DNA content in larvae resulting from activation of normal ova of sterlet with the treated sperm showed low efficiency of haploid gynogenesis induction. The putative gynogenetic larvae were found after treatment with PS in concentrations higher than 18µM and EB higher than 10µM followed by UV-A irradiation at the dose of 900 J/m2 and DMS up to 5mM. Because of an overwhelming impact on the sperm motility and relatively low DNA damage, treatment of sperm with PS, EB or DMS did not prove efficient compared with a widely used UV-C irradiation treatment. In contrast, treatment with AMT followed by UV-A showed lower influence on spermatozoa motility and higher efficiency of DNA damaging resulting in the higher percentage of gynogenotes in the progeny, thus could be considered as a possible substitution for UV-C treatment.

In 2014, the journal Plant Protection Science (PPS) completes 50 years of publication (1965-2014). However, its roots extend back to the year 1921. Today, it is an international scientific journal focused on all aspects of plant protection sciences, fully published in English. This occasion offers a fitting opportunity to describe some of the most important historical stages of the journal's development. In our brief historical overview, we summarise the changes in journal title, chief-editors, and editorial policy during the last fifty years, and with an examination of its importance, scope and readership. We present analyses of the journal's development, some for the entire period of 1965-2013, while others are limited to more recent decades. The journal's present place among the world's scientific journals is documented by analyses in the international citation databases, BIOSIS CI, SCOPUS, and WOS. An analysis of three particular citation databases were made in October 2013, while the overall period 1998-2013 was conducted from All Databases/Thomson Reuters in March 2014. PPS is also included in other, important technical-literature databases, including Czech Agricultural and Food Bibliography, AGRIS/FAO database, AGRICOLA, CAB Abstracts, Current Contents, and Zoological Abstracts. Information about all of them is available in Ulrich's WEB database. In the final part of this paper, we summarise some recent achievements of the journal, and discuss some key topics related to its future development.

In 2007-2012 the first detailed study of P. halstedii distribution and severity was performed in the Czech Republic by monitoring altogether 128 localities. Incidence of the pathogen was recorded at seven localities in south-eastern (Central and South Moravia) and central parts (East and Central Bohemia) of the country; at only four localities the occurrence of sunflower downy mildew symptoms and pathogen sporulation were recorded repeatedly. In all cases the primary infection prevailed, and the severity of infections was rather low. The majority of records were for sunflower experimental fields (e.g. fields of Central Institute for Supervising and Testing in Agriculture. Brno-Chrlice, Czech Republic), one record came from a commercial field and one record from a hobby field. Results of surveys indicate that reservoirs of primary inoculum likely exist in the soil contaminated by P. halstedii oospores in these habitats, but additional transfer by infected seed may be possible. Historical and geographical consequences of recorded infections are discussed, as well as virulence variation in the Czech pathogen populations which is currently in the process of investigation.

Our biotechnological research on selected Cucumis species has encompassed interspecific hybridization via embryo-rescue, in vitro pollination, somatic hybridization and cytogenetics of protoplasts. Embryo-rescue and in vitro pollination are suitable in vitro techniques for production of hybrid embryos. These methods were tested and optimized for cucurbits. Protoplast culture is another valuable tool for biotechnological applications, such as somatic hybridization and genetic transformation. We study protoplast dedifferentiation not only as a biotechnological application in breeding systems, but mainly to describe mechanisms of obtaining totipotency. Protoplasts of cucurbits were studied cytogenetically to observe changes in nuclear architecture during protoplastization and regeneration and for comparison with the expression profile obtained using cDNA-AFLP techniques and reverse transcription for the specific genes involved.

Lettuce (Lactuca sativa) is the most important crop in the group of leafy vegetables. It is characterized by considerable morphological and genetic variation. The crop comprises seven main groups of cultivars (including oilseed lettuce) differing phenotypically; they are usually described as morphotypes. Lettuce breeding is primarilly focused on various morphological features and resistance against diseases and pests. The accurate description of lettuce germplasm provides basic information useful for lettuce breeders. The construction of a lettuce descriptor list has been stimulated by the international genebank community. This list consists of 55 descriptors with 15 elucidated by figures. It provides a tool for detailed characterization of and discrimination within the intraspecific variation of L. sativa, verification of old varieties, and identification of putative duplicates and gaps in germplasm collections. These descriptors, along with descriptors of wild Lactuca species, provide an efficient analytical tool for studying the complex morphological variability of this genus and relationships among the species.

During the summer of 2007 in a private garden in Smržice (district Prostějov, Czech Republic) symptoms of powdery mildew on Caragana arborescens were recorded. Until now at least two powdery mildew species (Microsphaera trifolii var. trifolii and M. palczewskii), both differing in some basic morphological features, have been recorded for the genus Caragana. Comparison of our measurements with previous descriptions of powdery mildew samples found in the Czech Republic on Caragana arborescens identified our species as Microsphaera palczewskii (newly Erysiphe palczewskii). This is probably the first detailed record of this species on C. arborescens in the Czech Republic. Fungus from Czech Republic was compared with the material collected in 2007 in Vienna (Austria). The aim of this paper was to provide a detailed comparative morphological characterisation of E. palczewskii anamorph and teleomorph found in the Czech Republic and in Austria. Serious reduction of the anamorph, caused by hyperparasitic fungus Ampelomyces quisqualis, was recorded on the sample from Austria.

The genus Lactuca L. belongs to one of the largest plant families, Asteraceae. Lactuca L. is represented by ca 100 species distributed in different geographical areas and ecological conditions. This is one of the reasons why this genus is characterised by very broad variation of different characters. Electrophoretic detection of some proteins (isozymes) has been applied to the study of genetic variability of Lactuca spp. individuals and populations. The development of molecular genetic methods (RFLP, Restriction Fragment Length Polymorphism; PCR methods: RAPD, Random Amplified Polymorphic DNA; AFLP, Amplified Fragment Length Polymorphism; minisatellites and microsatellites fingerprinting or SSR, Simple Sequence Repeats) and their application has contributed to the elucidation of various aspects related to the taxonomy, variability, biodiversity, genetics and breeding within the genus Lactuca L. Further potential application of these methods is discussed.

The influence of inoculation techniques on induction of post-infection ethylene production in susceptible and resistant genotypes of bean (Phaseolus vulgaris) inoculated with the kappa race of Colletotrichum lindemuthianum was studied. Three inoculation methods (brushing, dipping and spraying) of excised leaves were compared. The brushing technique caused both the highest ethylene production at 120 h after inoculation, and better symptom development than dipping and spraying. It was, therefore, adopted to determine the post-infection ethylene production in four inoculated bean genotypes (GLP406 and Kaboon - resistant, GLP636 - moderately resistant; and MDRK - susceptible). Ethylene production increased slightly 24 h after inoculation in all four genotypes, followed by a rapid decline after 48 h. Ethylene production remained low until 120 h after which a sharp rise was observed in genotype MDRK. Increased production, though to a lesser extent, was observed in GLP636. This trend was repeatable and thus may offer an additional physiological marker to bean breeders to screen for resistance to C. lindemuthianum.

Fifty one accessions of nineteen Lactuca species, the hybrid L. serriola × L. sativa and the related species Mycelis muralis were evaluated for morphological variability, esterase (EST) polymorphism, Amplified Fragment Length Polymorphism (AFLP) and relative DNA content. Sixteen Lactuca accessions were classified taxonomically on the basis of morphology, isozyme analysis and AFLP. Twenty-eight bands (isoforms) of EST were recorded allowing 82% of accessions to be distinguished. The relative DNA content, measured using flow-cytometry (DAPI staining), ranged from 2.02 pg in L. capensis to 17.96 pg in L. canadensis. The results from AFLP analysis and the relative DNA content measurement corresponded well with recent taxonomic classification of the genus Lactuca.

The activities of amine oxidase, peroxidase and catalase were studied in 12 cultivars of field pea (Pisum sativum L.) and one accession of wild pea (Pisum sativum subsp. transcaucasicum). The influence of different light conditions on the enzyme activities was studied in extracts of 8-d-old seedlings. Substantially higher amine oxidase activity was detected in etiolated pea seedlings than in plants growing under controlled light conditions (12h photoperiod). Higher peroxidase and catalase activities indicate more intensive production of toxic hydrogen peroxide evolved by reactions of different type in green plants in comparison with etiolated ones. Significantly lower activity of peroxidases in etiolated plants could be related to a lower degree of lignification. Marked differences in enzyme activities between etiolated field pea and P. sativum subsp. transcaucasicum were observed for all studied enzymes. A very interesting result was the exceptionally low activity of amine oxidase in etiolated plants that was hardly detectable in green plants of Malton cultivar. Two bands with amine oxidase activity were found by the method of native PAGE in extracts of 8-d-old plants. A different relationship of these isoenzymes was detected in field pea and wild pea. Two isoenzymes were present in pea shoots but only one isoenzyme was detected in pea roots. Amine oxidase isoenzymes were studied in the roots and shoots of cv. Smaragd for three weeks. The profile of isoenzymes was opposite in 8- and 36-d-old stems of pea.

A set of 15 accessions of maca, Lepidium meyenii Walp., and 25 accessions of yacon, Smallanthus sonchifolius (Poepp. & Endl.) H. Robins., cultivated under Czech field conditions was studied to determine relationships between morphological variability and isozyme polymorphisms. Morphological characterisation of maca included evaluation of length, weight, shape, skin and flesh colour of hypocotyls. In yacon, we evaluated shape, colour, skin texture and flesh colour of tubers, as well as the number of roots. Preliminary results showed that maca forms low-weight hypocotyls (up to only 17.4 g) under Czech field conditions. For yacon, tuber production ranged between 1.4 kg and 3.8 kg. Of the 17 analysed enzymatic systems, only esterase (EST) showed some degree of polymorphism in both crops. It was possible to divide accessions of L. meyenii into two groups and S. sonchifolius into six groups on the basis of isozyme polymorphisms. However, EST polymorphisms do not correspond very well to the morphological characteristics of the underground organs of the crops studied.

Czech collections of Cucumis spp. genetic resources includes 895 accessions ofcultivated C. sativus and C. melo species and 89 accessions of wild species. Knowledge of their morphological and biological features and a correct taxonomical ranging serve a base for successful use of germplasm in modern breeding. List of morphological descriptors consists of 65 descriptors and 20 of them are elucidated by figures. It provides a tool for Cucumis species determination and characterization and for a discrimination of an infraspecific variation. Obtained data can be used for description of genetic resources and also for research purposes.

Of about 100 Lactuca species, there are only 22 represented in world gene bank collections. The description of morphological and other important features of wild lettuce accessions and a correct taxonomic ranging increase their potential successful utilization. A broad study of 22 wild Lactuca species, their morphology, anatomy, karyology, DNA content and isozyme variation, and a search of large number of literature sources (description keys, floras, monographs) provided a base for an elaboration of a descriptor set. This set consists of 88 descriptors and 24 of them are elucidated by figures. It provides a tool for Lactuca species characterization and determination and for a discrimination of an infraspecific variation. Obtained data can be used for description of wild Lactuca genetic resources and also for research purposes.

Fusarium Link (1809) is an anamorph genus with worldwide distribution and a remarkable degree of biodiversity. Its species are common in soil and have been found on a very wide range of vascular plants. Some specialized species are parasitic on other fungi and or insects. In the system of fungi the genus Fusarium is classified in the class Hyphomycetes which belongs to the Deuteromycotina. Teleomorphs have been placed in the genera Nectria and Gibberella, order Hypocreales (Ascomycetes). The taxonomy of the genus Fusarium is not settled and the number of species and sections varies. A few recent classification systems of this genus exist. Fusarium spp. have mostly been studied in the context of their ability to cause diseases of many economically important crop plants. Some species produce mycotoxins and other metabolites that can be harmful to humans and livestock. There is a wide variability in pathogenicity, and in many Fusarium spp. various formae speciales (f.sp.) and physiological races are known. In this paper a description of the 14 most important soil and plant pathogenic Fusarium spp. is provided.

The present paper tries to demonstrate progress and gap of knowledge in plant pathology through the tomato - tomato powdery mildew host-pathogen interaction as a model. Tomato powdery mildew (Oidium lycopersici) has caused serious damages on glasshouse tomato (Lycopersicon esculentum) crops during the last approximately 15 years. Although the absence of tcleomorph stage did not allow exact taxonomic classification of the pathogen, comparative morphological studies using light and scanning electron microscopy revealed that Oidium lycopersici might be included to the Erysiphe sect. Erysiphe (close to Erysiphe aqui­ legiae var. ranunculi). Effective resistance sources to 0. lycopersici were found mainly in wi ld Lycopersicon hirsutum and L. penne/lii (confirmed by testing with four different 0. lycopersici isolates). Available information on the pathogenic variability of 0. lycopersici is given; host range experiments revealed considerable differences in abi lity of different 0. lycopersici isolates to infect cucumber and tobacco. postulating existence of different pathotypcs lformae specialist of pathogen. Similarly, some Lycopersicon spp. genotypes showed remarkable differential reactions with pathogen isolates, indicating existence of different pathogen races. Information regarding recently detected mechanisms and basis of resistance in Lycopersicon spp. are also men­ tioned. However, more research based on classical, biochemical and molecular approaches is also needed.

The study was focused on the wild pathosystem Lactuca serriola-lettuce downy mildew (Bremia lactucae) and lettuce powdery mildew (Golovinomyces cichoracearum). Observations were focused mainly on recording natural infection of prickly lettuce (Lactuca serriola) by downy and powdery mildews in the East Bohemia and Moravia (the Czech Republic) in the May-September period of 2007-2011, and on the influence of environmental conditions on disease incidence. Only data for July and August were used for the detailed comparisons of occurrence of both pathogens, because intensity of disease in this period was the highest. Data were linked with the average monthly temperature and rainfall rate in the Czech Republic. G. cichoracearum prefers rather low levels of precipitation and temperatures around 20°C, therefore significantly higher incidence of this pathogen was recorded in August 2007. On the other hand in July 2009 and 2010, when the intensities of precipitation were higher, incidence of Bremia lactucae prevailed. In August 2010 and 2011 incidence of both pathogens were more or less similar at all locations. Our observations showed that climatic conditions influence the incidence and prevalence of both pathogens in weedy growing populations of Lactuca serriola.

Changes in Hsp70 gene expression and protein level were studied in three Solanum spp. genotypes in response to short-term high and low temperatures and to infection by powdery mildew. Development of Oidium neolycopersici was compared on plant leaves and leaf discs with regard to the influence of temperature. Heat and especially cold pre-treatment of host tissues inhibited pathogenesis and decreased chlorophyll concentration. Exposure to heat increased Hsp70 (70 kDa heat shock proteins) content in all three genotypes of Solanum spp., whereas the infection induced the accumulation of Hsp70 only in susceptible S. lycopersicum. These results are in accordance with the suggested role of Hsp70 chaperons in plant responses to metabolic pathway disturbances triggered by pathogen challenge.

Reactions of Lactuca spp. genotypes with different mechanisms of compatibility/incompatibility to B. lactucae race NL16 were examined. Microscopical study revealed significance of initial stages of infection for establishment of the host-pathogen relation. Incompatibility to the pathogen race is mostly expressed as hypersensitive reaction (HR). Rearrangement of cytoskeleton can participate in blocking of fungus penetration in resistant genotypes as well as support development of fungal infection structures in susceptible ones. During infection process peroxidase is activated, H2O2 released and phenolic compounds deposited. These defence processes well correspond with the expression of resistance. On the other hand, formation of callose attending pathogenesis is not directly related to incompatibility.

Two ectoparasite powdery mildew species Golovinomyces cichoracearum (Gc) and Podosphaera xanthii (Px) occurring on cucurbits differ, besides other characteristics, by specific ecologic requirements. While Px is common in subtropical and tropical areas and greenhouse crops, Gc occurs more frequently in temperate and cooler areas under field conditions. Their presence on cucurbit field crops (Cucurbita pepo, C. maxima, Cucumis sativus) was monitored in the Czechoslovakia (1979-1980) and in the Czech Republic (1995-2007). Their identification was carried out by microscopic observation of the morphological characteristics of the dry conidia on 1527 leaf samples. Data on air temperature in 1979-2007 were provided by the Czech Hydrometeorological Institute. In 1979-1980 Gc was identified in 86.0% of samples, Px in 14.0% samples, there was no mixed infection; prevalence of Px was recorded in South Slovakia and South Moravia, and on crops under cover. Since 1995 species Px was recorded each year on field crops in different locations of Bohemia and Moravia, usually in mixed infection with Gc. The average year temperature of 8.1°C for period 1992-2007 was higher than corresponding value of 7.4°C in 1979-1983. Similarly, average temperature in vegetation season of 16.2°C in 1992-2007 was higher than corresponding value of 15.7°C in 1979-1983. The higher air temperature can positively influence spreading of Px in the Czech Republic. Climate variability and effect of their changes are discussed in relationship to the geographic distribution and geographic patterns of cucurbit powdery mildews.

Limited information on the resistance mechanisms in Lycopersicon spp. to Oidium neolycopersici is still available. Macroscopically the resistance is characterized by a very low amount of mycelium development and a lack of sporulation. The leaf surface did not effectively inhibite conidium germination, however significant differences in germ tube and appressorium development were recorded. A large variation was observed in host tissue response. The prevailing resistance mechanism was hypersensitivity (HR). Considerable changes of peroxidase and catalase activities during pathogenesis were detected among tested wild Lycopersicon spp. There was positive correlation between increasing of peroxidase activity and extent of necrosis. Histochemistry showed large differences in production of superoxid ions, H2O2 and peroxidase in Lycopersicon spp. with various level of resistance.