Evsey Kosman

Tel Aviv University | TAU · Department of Molecular Biology and Ecology of Plants

It has been established that Nei's measure of the average genetic diversity per locus, HS, and the measure of average differences between isolates with respect to simple mismatch dissimilarity, are identical measures of diversity within populations. The Müller index of diversity can be considered as the correction of Nei's measure for small samples...

Determining true genetic dissimilarity between individuals is an important and decisive point for clustering and analysing diversity within and among populations, because different dissimilarity indices may yield conflicting outcomes. We show that there are no acceptable universal approaches to assessing the dissimilarity between individuals with m...

Measures of diversity within populations, and distance between populations, are compared for organisms with an asexual or mixed mode of reproduction. Examples are drawn from studies of plant pathogenic fungi based on binary traits including presence/absence of DNA bands or virulence/avirulence to differential hosts. Commonly used measures of popula...

A total of 353 urediniospore isolates of Puccinia striiformis f. sp. tritici (Pst) collected in Israel during 2001-2019 were analyzed. Pst pathogenicity was studied with a set of 20 differentials (17 Avocet and 3 other lines). Three periods were compared: 2001–2007, 2009–2016, and 2017–2019. No virulence to Yr5 and Yr15 was detected. Virulence freq...

Variation among Puccinia triticina isolates collected from triticale in Poland between 2012 and 2015 was studied based on virulence and simple sequence repeat (SSR) markers. Two hundred forty‐two single‐uredinial isolates from four geographically separated locations were tested for virulence against 33 near‐isogenic Thatcher lines containing known...

Variability of the Russian population of Puccinia triticina from durum wheat was studied with virulence and simple sequence repeat (SSR) markers. The pathogen was sampled during 2017 to 2019 in all regions with sizable durum wheat (Triticum durum) growing areas from winter (North Caucasus) and spring (Middle Volga, Ural, and West Siberia) wheat. A...

Cucurbit powdery mildew (CPM) is caused most frequently by well‐differentiated obligate erysiphaceous ectoparasites Golovinomyces orontii and Podosphaera xanthii, which vary in their ecology and virulence. All economically important cucurbit crops host both of these CPM species. Breeding of cucurbits for CPM resistance is highly important worldwide...

The aim of the present study was to validate new simple sequence repeat (SSR) markers and use them to assess genetic variability among 24 isolates of Puccinia triticina collected from wheat (Pt‐wheat) and triticale (Pt‐triticale) and 15 isolates of P. recondita f. sp. secalis (Prs) collected from rye. The Pt and Prs isolates were tested for virulen...

The metric of functional evenness FEve is an example of how approaches to conceptualizing and measuring functional variability may go astray. This index has several critical conceptual and practical drawbacks: • Different values of the FEve index for the same community can be obtained if the species have unequal species abundances; this result is...

Leaf rust, caused by the fungus Puccinia triticina Eriks., is one of the most damaging rust diseases of wheat in Russia. Population of P. triticina has been consistently monitored in seven regions of Russia since 2001. A total of 5191 single urediniospore isolates from bread wheat (Triticum aestivum) were analyzed during 2001–2018. The pathogen pop...

Background: Gene and protein interaction data are often represented as interaction networks, where nodes stand for genes or gene products and each edge stands for a relationship between a pair of gene nodes. Commonly, that relationship within a pair is specified by high similarity between profiles (vectors) of experimentally defined interactions o...

Leaf rust, caused by the fungus Puccinia triticina Eriks., is the most common rust disease of wheat in wheat‐producing areas worldwide. The Israeli population of P. triticina has been consistently monitored since 1993. A total of 784 single urediniospore isolates from Triticum aestivum were analyzed during 2000–2015. The structure of the pathogen p...

Aim Conservation planning and prioritization generally have focused on protecting taxa based on assessments of their long‐term persistence or on protecting habitats and sites with high species richness. An implicit assumption of these approaches is that species are equally different from each other. We propose metrics for conservation planning and...

Classical virulence analysis is based on discovering virulence phenotypes of isolates with regard to a composition of resistance genes in a differential set of host genotypes. With such a vision, virulence phenotypes are usually treated in a genetic manner as one of two possible alleles, either virulence or avirulence in a binary locus. Therefore,...

Microsatellites (simple sequence repeats, SSRs) still remain popular molecular markers for studying neutral genetic variation. Two alternative models outline how new microsatellite alleles evolve. Infinite alleles model (IAM) assumes that all possible alleles are equally likely to result from a mutation, while stepwise mutation model (SMM) describe...

Recently, the notion of diversity, which is directed towards (effective) numbers of types (states of a trait such as species and genotypes), is increasingly used as an umbrella term akin to “variation”, thus including classical metrics of dispersion among others. This is probably due to the growing interest in functional aspects of variation which...

The article “Structural type diversity: measuring structuredness of communities by type diversity”, written by H.-R. Gregorius and E. Kosman, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 15 January 2018 with open access.

Kosman diversity models were applied to analyses of virulence (disease reaction patterns) variation of 115 isolates of two cucurbit powdery mildew (CPM) species, Golovinomyces orontii (Go) and Podosphaera xanthii (Px), collected in the Czech Republic from 2010 through 2012. Diversity within and distances between Go and Px populations and each other...

Genetic variation between different populations of Puccinia triticina from Russia and Kazakhstan was evaluated, based on 18 simple sequence repeat (SSR) markers. Seventeen collections of P. triticina (181 single-uredinial isolates, in total) obtained from 15 different host species belonging to Aegilops and Triticum were included in the study. All s...

Background: The persistence of high genetic variability in natural populations garners considerable interest among ecologists and evolutionary biologists. One proposed hypothesis for the maintenance of high levels of genetic diversity relies on frequency-dependent selection imposed by parasites on host populations (Red Queen hypothesis). A complem...

A collection of Puccinia triticina isolates was characterized for polymorphism of microsatellite loci and estimated for their differentiation by geographic origin. The collection included 20 isolates from the Ural region, 31 from West Siberia, 53 from Central Europe, 32 from the Northwest region, 32 from the Volga region, and 40 from the North Cauc...

We present a framework for biodiversity metrics that organizes the growing panoply of metrics. Our framework distinguishes metrics based on the type of information–abundance, phylogeny, function–and two common properties–magnitude and variability. Our new metrics of phylogenetic diversity are based on a partition of the total branch lengths of a cl...

Hybridization creates unique allele combinations which can facilitate the evolution of invasiveness. Frequent interspecific hybridization between the Siberian elm, Ulmus pumila, and native elm species has been detected in the Midwestern United States, Italy and Spain. However, Ulmus pumila also occurs in the western United States and Argentina, reg...

One aspect of biodiversity, functional diversity, reflects the functional role of species within a community as measured by species characteristics. We present a new metric, functional trait dispersion, based on the concept of species distinctiveness measured as the distance among species in the multidimensional space defined by trait values. This...

Dispersion and diversity are two variants of the notion of biological variation that are often not properly distinguished even though they address intrinsically disparate aspects. Dispersion focuses on the assessment of (variable) differences among individuals or types, while diversity focuses on the assessment of numbers of distinct types. Here, ‘...

Endophytes have profound impacts on plants, including beneficial effects on agriculturally important traits. We hypothesized that endophytes in wild plants include beneficial endophytes that are absent or underrepresented in domesticated crops. In this work, we studied the structure of endophyte communities in wheat-related grasses, Triticum dicocc...

Israel and its vicinity constitute a center of diversity of domesticated wheat species (Triticum aestivum and T. durum) and their sympatrically growing wild relatives, including wild emmer wheat (T. dicoccoides). We investigated differentiation within the forma specialis of their obligate powdery mildew pathogen, Blumeria graminis f. sp. tritici (B...

Virulence of 347 single-uredinial isolates of Puccinia triticina from 16 species of Aegilops and Triticum grown in experimental fields with natural inoculum in Dagestan (Caucasus region of Russia) and Novosibirsk (West Siberian region of Russia) and in an artificially inoculated field in Shortandy (Northern Kazakhstan) was analyzed with 20 near-iso...

While wheat powdery mildew occurs throughout the south-central and eastern U.S.A, epidemics are especially damaging in the Mid-Atlantic states. The structure of the U.S. Blumeria graminis f. sp. tritici population was assessed based on a sample of 238 single-spored isolates. The isolates were collected from 16 locations in 12 states (18 site-years)...

In Kentucky bluegrass (Poa pratensis), Claviceps purpurea, the causal agent of ergot, typically releases ascospores during the early-morning hours, between about midnight and 10:00 A.M., corresponding to time of flowering, when the unfertilized ovaries are most susceptible to infection. During aeromycology studies of C. purpurea in perennial ryegra...

Leaf rust, caused by the fungus Puccinia triticina, is the most common rust disease of wheat in wheat-producing areas worldwide. The Israeli population of wheat leaf rust has been consistently monitored since 1993. A total of 840 single urediniospore isolates from Triticum aestivum (567), T. dicoccoides (119) and T. durum (154) were analysed during...

A total of 387 isolates of Puccinia graminis f. sp. tritici (Pgt) collected in the central region of the Russian Federation from 2000 to 2009 was analysed with North American differential sets comprising 16 genotypes for samples of 2000–2006 and 20 genotypes for samples from 2007–2009. Forty‐five races were identified. The race composition of the l...

We report the distribution and disease level of downy mildew on lettuce (Lactuca sativa) and virulence variation in populations of its causal agent (Bremia lactucae) in the Czech Republic during the period 1999–2011. Disease incidence was not high; among a total of 92 different localities surveyed, 43.4% of them were infected by lettuce downy milde...

Making inferences about variation within and among various operational units may depend on the ability of a selected approach to diversity analysis to utilize correctly all information available in the raw data. Frequency-based genotypic and gene diversity parameters, methods of 'true diversity' and functional diversity, as well as two types of dis...

The functioning and features of the new software package VAT (Virulence Analysis Tool) are introduced. VAT provides a range of methods for the analysis of plant pathosystems. The techniques are applicable to other binary data sets that are organized in large two-way tables, e.g., molecular marker data. The main features are data entry, descriptive...

Virulence analysis of 224 isolates of Blumeria graminis f. sp. hordei (barley powdery mildew) from South Africa was performed. The isolates were collected from eight fields and a greenhouse in 2004 and 2007. The isolates were tested for virulence on a set of 20 differential varieties. All isolates were virulent on the resistance genes Mla8 and Ml(C...

Four hundred and seventeen single-uredinial isolates of Puccinia triticina collected from wheat in seven regions of Russia in 2007 were tested for virulence with 24 near-isogenic wheat differential lines and molecular variation with six RAPD and one UP-PCR DNA markers. Seventy-nine virulence phenotypes and 71 molecular genotypes were identified. Th...

The structure of P. triticina populations collected in Northwest region of Russian Federation in 2007 was studied by virulence and DNA-markers. 35 virulence phenotypes and 37 DNA-phenotypes were detected among 139 isolates. It was determined that virulence diversity was much higher within the samples from Pskov and Leningrad populations collected o...

Stripe rust of wheat (Triticum spp.), caused by Puccinia striiformis f. sp. tritici, is an important disease in Ethiopia. To investigate the population structure of the pathogen, 107 single-pustule isolates were collected from four regions (northern, central, southern, and southeastern Ethiopia) and tested on 24 differential genotypes with known re...

The effects of air pollutants, weather conditions, airborne pollen and spores on the incidence of emergency room (ER) visits of children for acute asthma attacks were investigated. One-year retrospective study was done. Data on daily concentrations of air pollutants, airborne allergens and weather conditions were collected and compared with the ER...

ABSTRACT Eleven previously published models of plant disease epidemics, given as differential equations with a rate and a shape parameter, are compared using general model characteristics as well as their usefulness in fitting observed data. Six out of the eleven models can be solved analytically resulting in epidemic growth functions, while the ot...

A new approach for modelling epidemics caused by fungal foliar plant pathogens is presented. The model is described by a system of differential equations, and is simple enough to allow a qualitative analytical study of the main epidemiological factors that determine the rate of disease progress during a single growing period. The model was analysed...

Three hundred and nine isolates were obtained from three natural populations of Blumeria graminis f. sp. hordei occurring on wild barley (Hordeum vulgare subsp. spontaneum) at two locations in Israel during 1997 and 1999. Their virulence frequency was determined on 32 differential lines. No isolate was virulent on the differential lines possessing...

Digital image analysis was used to measure dimensions of spores produced by Puccinia coronata, P. graminis, P. hordei, P. recondita, P. striiformis and P. triticina. Included were teliospores, basidiospores, urediniospores and, except for P. striiformis, pycniospores and aeciospores. Length, width and projection area of spores were measured with NI...

Digital image analysis was used to measure dimensions of spores produced by Puccinia coronata, P. graminis, P. hordei, P. recondita, P. striiformis and P. triticina. Included were teliospores, basidiospores, urediniospores and, except for P. striiformis, pycniospores and aeciospores. Length, width and projection area of spores were measured with NI...

The air that we inhale contains simultaneously a multiple array of allergenic pollen. It is well known that such allergens cause allergic reactions in some 15 of the population of the Western World. However little is known about the quantitative aspect of this phenomenon. What is the lowest concentration of pollen that might trigger allergic respon...

ABSTRACT The genetic relationships between isolates of Puccinia triticina virulent on wheat with the Lr26 resistance gene were studied. The diversity within and between isolates of P. triticina from Israel, Europe, and the United States was determined by virulence on near-isogenic Thatcher lines and by random amplified polymorphic DNA. According to...

ABSTRACT The measure of multilocus correlation for diallelic loci was developed to augment use of other diversity indices in the study of multilocus structure of populations. This measure provides information not revealed by other parameters for measuring multilocus association and linkage disequilibrium among pairs of loci. Relationships between t...

The separation of plant and fungal sequences in EST pools by bioinformatic methods is difficult because of sequence similarities between plants and fungi, lack of enough sequence information, and the short length of the isolated fragments. An algorithm and software that utilize the differences in codon usage bias to discriminate between plant and f...

Collections of Puccinia triticina were obtained from rust-infected wheat leaves by cooperators throughout the United States and from surveys of wheat fields and nurseries in the Great Plains, Ohio Valley. Gulf Coast, California, Pacific Northwest, and Atlantic Coast States in order to determine the virulence of the wheat leaf rust fungus in 2001. S...

Methodological aspects of stochastic variation were considered on example of bioassay for estimation of fungicide resistance (KADISH & COHEN 1988). The corresponding probabilistic model for measuring frequency of fungicide resistant phenotype in a plant pathogen population was developed. Unpredictable relationships between estimates from the model...

ABSTRACT Isolates of Puccinia recondita f. sp. tritici (n = 260) obtained from bread, durum, and wild emmer wheat leaf collections throughout Israel during 1993 to 1997 were analyzed for virulence on a set of wheat differentials. The overall frequency of virulence increased on differentials possessing resistance genes Lr1, Lr2a, Lr3, and Lr26 and d...

The worldwide increase in the incidence, prevalence, and severity of asthma may suggest that environmental factors play a role in these epidemiologic changes. To examine the correlations between air pollutants, weather conditions, airborne allergens, and the incidence of emergency room (ER) visits of children with acute asthma attacks. One-year pro...

It is not easy to identify the specific plant species that causes an allergic response in a certain patient at a certain time. This is further complicated by the fact that closely related plant species cause similar allergic responses. A novel mathematical technique is used for analysis of skin responses of a large number of patients to several gro...

The responses of 148 atopic patients to some 43 different extracts of allergenic pollen were tested by prick tests. The measure of dissimilarity was introduced and calculated for all pairs of allergens. The investigated allergens were clustered into groups, according to their unbiased greatest similarity, by a matrix-structuring method. Results ind...

We consider the Sylow p-subgroups, obtained by completion, of the restricted linear group of a countable-dimensional vector space of countable cardinality over a finite field of characteristic p. The geometric approach of O'Meara is used to describe the isomorphisms of linear groups that are not rich or even sufficiently rich in transvections. We p...

General overview KOIND is a package of computer programs calculating several indices of diversity within and be-tween plant pathogen populations. Each included index measures diversity in a different way, em-phasizing different aspects of diversity. The calculations are based on the bootstrap method and allow to estimate indices as well as their va...