Evsey Kosman - Academia.edu (original) (raw)

Papers by Evsey Kosman

Plant Disease

A total of 353 urediniospore isolates of Puccinia striiformis f. sp. tritici (Pst) collected in I... more A total of 353 urediniospore isolates of Puccinia striiformis f. sp. tritici (Pst) collected in Israel during 2001 to 2019 were analyzed. Pst pathogenicity was studied with a set of 20 differentials (17 Avocet and 3 other lines). Three periods were compared: 2001 to 2007, 2009 to 2016, and 2017 to 2019. No virulence to Yr5 or Yr15 was detected. Virulence frequencies on Yr4, Yr10, Yr24, and YrSp genes rose to the moderate level (0.28 to 0.44) in 2017 to 2019. Virulence frequencies to Yr2 and Yr9 decreased. One Pst phenotype was identified in all three periods, but its frequency drastically decreased from 0.74 in 2001 to 2016 to 0.21 in 2017 to 2019. The most probable scenario of emergence of wheat yellow rust in Israel is wind dissemination of Pst urediniospores from the Horn of Africa. Variability of the Pst population increased amid considerable evolution with two major transformations in 2009 and 2017. The first modification can be attributed to changes in wheat genetic background...

Figure S1. Cumulative similarity distributions between genetic interaction vectors under differen... more Figure S1. Cumulative similarity distributions between genetic interaction vectors under different similarity measures for the two-square transformation. (PDF 179 kb)

Theoretical Ecology, 2018

Recently, the notion of diversity, which is directed towards (effective) numbers of types (states... more 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 involve variable differences between types. Though the traditional notion of diversity does not cover these aspects, it shows up in many interpretations. To overcome this ambiguity, the traditional notion of diversity is extended in this paper to include variable differences with emphasis on their general significance as structuring features. For this purpose, structure is conceived to be captured by the representation of types via variable differences and abundances. Structural diversity then results from application of traditional measures of diversity to the relative structural representations of types in addition to their relative abundances. Since diversity as effective number of types alone provides no information about their mutual distinctness and the range covered by them, connections to measures of dispersion are indispensable. This is considered via two approaches that rely on dispersion characteristics and one approach that allows for an assessment of structural diversity for controlled levels of type distinctness. Effects of structure on dispersion and diversity are analyzed. The use of the approaches for discovering rarely considered characteristics of phylogenetic structure is demonstrated.

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Table S1. Statistics of similarity scores between yeast genetic interaction vectors under differe... more Table S1. Statistics of similarity scores between yeast genetic interaction vectors under different similarity measures for the two-square matrix. (DOC 12 kb)

Phytopathology®, 2019

Classical virulence analysis is based on discovering virulence phenotypes of isolates with regard... more 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, population genetics metrics and methods have become prevailing tools for analyzing virulence data at multiple loci. However, a basis for resolving binary virulence phenotypes is infection type (IT) data of host–pathogen interaction that express functional traits of each specific isolate in a given situation (particular host, environmental conditions, cultivation practice, and so on). IT is determined by symptoms and signs observed (e.g., lesion type, lesion size, coverage of leaf or leaf segments by mycelium, spore production and so on), and assessed by IT scores at a generally accepted scale for each plant–pathogen system. Thus, multiple ...

European Journal of Plant Pathology, 2013

Making inferences about variation within and among various operational units may depend on the ab... more 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 dissimilarity based approaches (by means of averaging pairwise dissimilarities, and solution of the assignment problem) are comprehensively discussed. The dissimilarity based approaches need a suitable assessment of dissimilarity between individual operational units (individuals, communities, populations, clusters, functions, phylogenetic trees etc.). Many commonly used diversity parameters can be derived in terms of the average based measures. The assignment based methods are able to address some limitations and shortcomings of the commonly used measures of population diversity, and they are preferable in the case of possible association between traits. They are always mathematically valid, whereas validity of the average based methods depends on the selected dissimilarity measure. The dissimilarity based methods actually assess functional diversity in the space of the selected traits, and they allow measuring complex diversity and assessment of total γ-diversity as the sum of the independent components of αand β-diversity with descriptors of different types. The dissimilarity based method for diversity analysis can be consistently employed together with other approaches to data analysis (e.g. clustering). In particular, they may provide valid diversity estimates and replace Nei's diversity measures, which are often inconsistently used with binary molecular marker data.

BMC Ecology, 2017

Background: The persistence of high genetic variability in natural populations garners considerab... more 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 complementary hypothesis suggests that a trade-off between fitness costs associated with tolerance to stress factors and fitness costs associated with resistance to parasites is responsible for the maintenance of host genetic diversity. Results: The present study investigated whether host resistance to parasites is traded off with tolerance to environmental stress factors (high/low temperatures, high salinity), by comparing populations of the freshwater snail Melanoides tuberculata with low vs. high clonal diversity. Since polyclonal populations were found to be more parasitized than populations with low clonal diversity, we expected them to be tolerant to environmental stress factors. We found that clonal diversity explained most of the variation in snail survival under high temperature, thereby suggesting that tolerance to high temperatures of clonally diverse populations is higher than that of populations with low clonal diversity. Conclusions: Our results suggest that resistance to parasites may come at a cost of reduced tolerance to certain environmental stress factors.

Plant Disease

Variability of the Russian population of Puccinia triticina from durum wheat was studied with vir... more 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 total of 474 isolates were tested on a set of 20 Lr-gene lines. Molecular genotypes for 105 selected isolates were determined at 11 SSR loci. Variable virulence/avirulence reaction was observed only on three Lr-gene lines, whereas just five SSR loci were polymorphic with two alleles at each. Seven different virulence phenotypes and 11 SSR genotypes were found among 474 and 105 isolates, respectively, indicating a very low variability of the pathogen. One virulence phenotype and three SSR genotypes occurred in all Russian regions. However, two phenotypes were specific to the European regions of Russia (North Caucasus and Middle Volga), whil...

BMC Bioinformatics

Background: Gene and protein interaction data are often represented as interaction networks, wher... more 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 of each of the two genes with all other genes in the genome; only gene pairs that interact with similar sets of genes are linked by an edge in the network. The tight groups of genes/gene products that work together in a cell can be discovered by the analysis of those complex networks. Results: We show that the choice of the similarity measure between pairs of gene vectors impacts the properties of networks and of gene modules detected within them. We re-analyzed well-studied data on yeast genetic interactions, constructed four genetic networks using four different similarity measures, and detected gene modules in each network using the same algorithm. The four networks induced different numbers of putative functional gene modules, and each similarity measure induced some unique modules. In an example of a putative functional connection suggested by comparing genetic interaction vectors, we predict a link between SUN-domain proteins and protein glycosylation in the endoplasmic reticulum. Conclusions: The discovery of molecular modules in genetic networks is sensitive to the way of measuring similarity between profiles of gene interactions in a cell. In the absence of a formal way to choose the "best" measure, it is advisable to explore the measures with different mathematical properties, which may identify different sets of connections between genes.

Frontiers in Agronomy

Management of wheat stem rust in Western Siberia has gained importance since the first outbreaks ... more Management of wheat stem rust in Western Siberia has gained importance since the first outbreaks in 2007–2010 and 2016. The race composition and virulence patterns were investigated for the enlarged Puccinia graminis f. sp. tritici (Pgt) samples collected in three neighboring regions Omsk, Novosibirsk, and Altai during 2017–2018. Most of Pgt isolates were identified as virulent to wheat lines with genes Sr5, Sr9a, Sr10, Sr38, SrMcN, and avirulent to Sr24, Sr31. Differentiation ability of genes Sr6, Sr7b, Sr8a, Sr9b, Sr9d, Sr9g, Sr9e, Sr11, Sr17, Sr21, Sr30, Sr36, and SrTmp to distinguish between the regional populations was established. A total of 33 virulence phenotypes or races were detected among 115 Pgt isolates tested. Based on virulence phenotypes, two different Pgt subpopulations were identified in the Altai and Omsk regions likely originating from asexual and sexual cycles, respectively. The Novosibirsk pathogen population seems to be a mixture of isolates originated from both neighboring regions with virulence phenotypes that developed in the west, Omsk (TKRPF, QHHSF, and MLLTF), and in the south, Altai (NFMSF, LKCSF, LKMSF, and PKCSF), of Western Siberia.

Methods in Ecology and Evolution

Environmental Microbiology

Theoretical Ecology

In a general sense, a metacommunity can be considered as a network of communities, the coherence ... more In a general sense, a metacommunity can be considered as a network of communities, the coherence of which is based on characteristics that are shared by members of different communities, whatever forces were responsible (dispersal, migration, local adaptation, etc.). The purpose is to show that by basing the assessment of coherence on the degree of nestedness of one community within another with respect to the shared characteristics, coherence components can be identified within the network. To assess coherence, a measure of nestedness is developed, and its application to complex (variable) object differences (including multiple traits or characters) is investigated. A community network is then viewed as a graph in which the nodes represent the communities and the edges connecting nodes are weighted by the reverse of the degrees of nestedness between the corresponding communities. Given this framework, it is argued that a minimum requirement for a set of communities to be coherent i...

Plant Disease

A total of 353 urediniospore isolates of Puccinia striiformis f. sp. tritici (Pst) collected in I... more A total of 353 urediniospore isolates of Puccinia striiformis f. sp. tritici (Pst) collected in Israel during 2001 to 2019 were analyzed. Pst pathogenicity was studied with a set of 20 differentials (17 Avocet and 3 other lines). Three periods were compared: 2001 to 2007, 2009 to 2016, and 2017 to 2019. No virulence to Yr5 or Yr15 was detected. Virulence frequencies on Yr4, Yr10, Yr24, and YrSp genes rose to the moderate level (0.28 to 0.44) in 2017 to 2019. Virulence frequencies to Yr2 and Yr9 decreased. One Pst phenotype was identified in all three periods, but its frequency drastically decreased from 0.74 in 2001 to 2016 to 0.21 in 2017 to 2019. The most probable scenario of emergence of wheat yellow rust in Israel is wind dissemination of Pst urediniospores from the Horn of Africa. Variability of the Pst population increased amid considerable evolution with two major transformations in 2009 and 2017. The first modification can be attributed to changes in wheat genetic background...

Figure S1. Cumulative similarity distributions between genetic interaction vectors under differen... more Figure S1. Cumulative similarity distributions between genetic interaction vectors under different similarity measures for the two-square transformation. (PDF 179 kb)

Theoretical Ecology, 2018

Recently, the notion of diversity, which is directed towards (effective) numbers of types (states... more 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 involve variable differences between types. Though the traditional notion of diversity does not cover these aspects, it shows up in many interpretations. To overcome this ambiguity, the traditional notion of diversity is extended in this paper to include variable differences with emphasis on their general significance as structuring features. For this purpose, structure is conceived to be captured by the representation of types via variable differences and abundances. Structural diversity then results from application of traditional measures of diversity to the relative structural representations of types in addition to their relative abundances. Since diversity as effective number of types alone provides no information about their mutual distinctness and the range covered by them, connections to measures of dispersion are indispensable. This is considered via two approaches that rely on dispersion characteristics and one approach that allows for an assessment of structural diversity for controlled levels of type distinctness. Effects of structure on dispersion and diversity are analyzed. The use of the approaches for discovering rarely considered characteristics of phylogenetic structure is demonstrated.

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Table S1. Statistics of similarity scores between yeast genetic interaction vectors under differe... more Table S1. Statistics of similarity scores between yeast genetic interaction vectors under different similarity measures for the two-square matrix. (DOC 12 kb)

Phytopathology®, 2019

Classical virulence analysis is based on discovering virulence phenotypes of isolates with regard... more 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, population genetics metrics and methods have become prevailing tools for analyzing virulence data at multiple loci. However, a basis for resolving binary virulence phenotypes is infection type (IT) data of host–pathogen interaction that express functional traits of each specific isolate in a given situation (particular host, environmental conditions, cultivation practice, and so on). IT is determined by symptoms and signs observed (e.g., lesion type, lesion size, coverage of leaf or leaf segments by mycelium, spore production and so on), and assessed by IT scores at a generally accepted scale for each plant–pathogen system. Thus, multiple ...

European Journal of Plant Pathology, 2013

Making inferences about variation within and among various operational units may depend on the ab... more 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 dissimilarity based approaches (by means of averaging pairwise dissimilarities, and solution of the assignment problem) are comprehensively discussed. The dissimilarity based approaches need a suitable assessment of dissimilarity between individual operational units (individuals, communities, populations, clusters, functions, phylogenetic trees etc.). Many commonly used diversity parameters can be derived in terms of the average based measures. The assignment based methods are able to address some limitations and shortcomings of the commonly used measures of population diversity, and they are preferable in the case of possible association between traits. They are always mathematically valid, whereas validity of the average based methods depends on the selected dissimilarity measure. The dissimilarity based methods actually assess functional diversity in the space of the selected traits, and they allow measuring complex diversity and assessment of total γ-diversity as the sum of the independent components of αand β-diversity with descriptors of different types. The dissimilarity based method for diversity analysis can be consistently employed together with other approaches to data analysis (e.g. clustering). In particular, they may provide valid diversity estimates and replace Nei's diversity measures, which are often inconsistently used with binary molecular marker data.

BMC Ecology, 2017

Background: The persistence of high genetic variability in natural populations garners considerab... more 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 complementary hypothesis suggests that a trade-off between fitness costs associated with tolerance to stress factors and fitness costs associated with resistance to parasites is responsible for the maintenance of host genetic diversity. Results: The present study investigated whether host resistance to parasites is traded off with tolerance to environmental stress factors (high/low temperatures, high salinity), by comparing populations of the freshwater snail Melanoides tuberculata with low vs. high clonal diversity. Since polyclonal populations were found to be more parasitized than populations with low clonal diversity, we expected them to be tolerant to environmental stress factors. We found that clonal diversity explained most of the variation in snail survival under high temperature, thereby suggesting that tolerance to high temperatures of clonally diverse populations is higher than that of populations with low clonal diversity. Conclusions: Our results suggest that resistance to parasites may come at a cost of reduced tolerance to certain environmental stress factors.

Plant Disease

Variability of the Russian population of Puccinia triticina from durum wheat was studied with vir... more 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 total of 474 isolates were tested on a set of 20 Lr-gene lines. Molecular genotypes for 105 selected isolates were determined at 11 SSR loci. Variable virulence/avirulence reaction was observed only on three Lr-gene lines, whereas just five SSR loci were polymorphic with two alleles at each. Seven different virulence phenotypes and 11 SSR genotypes were found among 474 and 105 isolates, respectively, indicating a very low variability of the pathogen. One virulence phenotype and three SSR genotypes occurred in all Russian regions. However, two phenotypes were specific to the European regions of Russia (North Caucasus and Middle Volga), whil...

BMC Bioinformatics

Background: Gene and protein interaction data are often represented as interaction networks, wher... more 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 of each of the two genes with all other genes in the genome; only gene pairs that interact with similar sets of genes are linked by an edge in the network. The tight groups of genes/gene products that work together in a cell can be discovered by the analysis of those complex networks. Results: We show that the choice of the similarity measure between pairs of gene vectors impacts the properties of networks and of gene modules detected within them. We re-analyzed well-studied data on yeast genetic interactions, constructed four genetic networks using four different similarity measures, and detected gene modules in each network using the same algorithm. The four networks induced different numbers of putative functional gene modules, and each similarity measure induced some unique modules. In an example of a putative functional connection suggested by comparing genetic interaction vectors, we predict a link between SUN-domain proteins and protein glycosylation in the endoplasmic reticulum. Conclusions: The discovery of molecular modules in genetic networks is sensitive to the way of measuring similarity between profiles of gene interactions in a cell. In the absence of a formal way to choose the "best" measure, it is advisable to explore the measures with different mathematical properties, which may identify different sets of connections between genes.

Frontiers in Agronomy

Management of wheat stem rust in Western Siberia has gained importance since the first outbreaks ... more Management of wheat stem rust in Western Siberia has gained importance since the first outbreaks in 2007–2010 and 2016. The race composition and virulence patterns were investigated for the enlarged Puccinia graminis f. sp. tritici (Pgt) samples collected in three neighboring regions Omsk, Novosibirsk, and Altai during 2017–2018. Most of Pgt isolates were identified as virulent to wheat lines with genes Sr5, Sr9a, Sr10, Sr38, SrMcN, and avirulent to Sr24, Sr31. Differentiation ability of genes Sr6, Sr7b, Sr8a, Sr9b, Sr9d, Sr9g, Sr9e, Sr11, Sr17, Sr21, Sr30, Sr36, and SrTmp to distinguish between the regional populations was established. A total of 33 virulence phenotypes or races were detected among 115 Pgt isolates tested. Based on virulence phenotypes, two different Pgt subpopulations were identified in the Altai and Omsk regions likely originating from asexual and sexual cycles, respectively. The Novosibirsk pathogen population seems to be a mixture of isolates originated from both neighboring regions with virulence phenotypes that developed in the west, Omsk (TKRPF, QHHSF, and MLLTF), and in the south, Altai (NFMSF, LKCSF, LKMSF, and PKCSF), of Western Siberia.

Methods in Ecology and Evolution

Environmental Microbiology

Theoretical Ecology

In a general sense, a metacommunity can be considered as a network of communities, the coherence ... more In a general sense, a metacommunity can be considered as a network of communities, the coherence of which is based on characteristics that are shared by members of different communities, whatever forces were responsible (dispersal, migration, local adaptation, etc.). The purpose is to show that by basing the assessment of coherence on the degree of nestedness of one community within another with respect to the shared characteristics, coherence components can be identified within the network. To assess coherence, a measure of nestedness is developed, and its application to complex (variable) object differences (including multiple traits or characters) is investigated. A community network is then viewed as a graph in which the nodes represent the communities and the edges connecting nodes are weighted by the reverse of the degrees of nestedness between the corresponding communities. Given this framework, it is argued that a minimum requirement for a set of communities to be coherent i...