Afternoon Ascospore Release in Claviceps purpurea Optimizes Perennial Ryegrass Infection

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 ryegrass (Lolium perenne) in northeastern Oregon during 2008 to 2010 and 2013, a strain of C. purpurea was found that released ascospores in the afternoon, coinciding with flowering in perernrial ryegrass. Under controlled environmental conditions, sclerotia from perennial ryegrass and Kentucky bluegrass released spores in the afternoon and morning, respectively, consistent with tirning of spore release under field conditions. Internal transcribed spacer (ITS) sequences of single sclerotial isolates from Kentucky bluegrass and perennial ryegrass were consistent with C. putpurea, although minor variations in ITS sequences among isolates were noted. Differences between Kentucky bluegrass and perennial ryegrass isolates were observed in random amplified polymorphic DNA. Evidence is provided for adaptation of C. purpurea to perennial ryegrass by means of delayed spore release that coincides with afternoon flowering in perennial ryegrass

Blumeria_graminis_57_isolates_SSR_data_7_loci

The data in ' Blumeria_graminis_57_isolates_SSR.csv' were originally collected for Ben-David, R., Parks, R., Dinoor, A., Kosman, E., Wicker, T., Keller, B. & Cowger, C. (2016). Differentiation among Blumeria graminis f. sp. tritici isolates originating from wild vs. domesticated Triticum species in Israel. Phytopathology, 106, 861-870. https://doi.org/10.1094/PHYTO-07-15-0177-R. If you use the data in this file, please cite the original publication

Dissimilarity of individual microsatellite profiles under different mutation models: Empirical approach

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) describes microsatellite evolution as stepwise adding or subtracting single repeat units. Genetic relationships between individuals can be analyzed in higher precision when assuming the SMM scenario with allele size differences as a proxy of genetic distance. If population structure is not predetermined in advance, an empirical data analysis usually includes (a) estimating proximity between individual SSR profiles with a selected dissimilarity measure and (b) determining putative genetic structure of a given set of individuals using methods of clustering and/or ordination for the obtained dissimilarity matrix. We developed new dissimilarity indices between SSR profiles of haploid, diploid, or polyploid organisms assuming different mutation models and compared the performance of these indices for determining genetic structure with population data and with simulations. More specifically, we compared SMM with a constant or variable mutation rate at different SSR loci to IAM using data from natural populations of a freshwater bryozoan Cristatella mucedo (diploid), wheat leaf rust Puccinia triticina (dikaryon), and wheat powdery mildew Blumeria graminis (monokaryon). We show that inferences about population genetic structure are sensitive to the assumed mutation model. With simulations, we found that Bruvo's distance performs generally poorly, while the new metrics are capturing the differences in the genetic structure of the populations.ISSN:2045-775

cristatella_mucedo_kosman_jokela

197 individuals, 8 loci, NA as missing valu

SSRs_Puccinia_triticana_Russia

The data in 'SSRs_Puccinia_triticana_Russia.csv' were originally collected for Gultyaeva, E. I., Aristova, М. К., Shaidayuk, Е. L., Mironenko, N. V., Kazartsev, I. A., Akhmetova, A. & Kosman, E. (2017). Genetic differentiation of Puccinia triticina Erikss. in Russia. Russian Journal of Genetics, 53, 998-1005. https://doi.org/10.1134/S1022795417070031. If you use the data in this file, please cite the original publication

Virulence Diversity of Puccinia striiformis f. sp. Tritici in Common Wheat in Russian Regions in 2019–2021

Yellow (stripe) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a major disease of common wheat worldwide. Disease epidemics in Russia have been frequent and destructive, mostly in the North Caucasus. However, over the last 5 years, the significance of Pst has markedly increased in other Russian regions. Therefore, the Pst virulence diversity was investigated in Triticum aestivum in six geographically distant regions of the European (North Caucasus, North-West, Low Volga, Central Black Earth region, and Volga-Vyatka) and Asian (West Siberia) parts of Russia, with strongly different climates, environmental conditions, and growing wheat genotypes. Seventy-nine virulence pathotypes among 117 isolates were identified using the 12 Avocet Yr gene lines (Yr1, Yr5, Yr6, Yr7, Yr8, Yr9, Yr10, Yr15, Yr17, Yr24, Yr27, and YrSp) and eight supplemental wheat differentials (Heines VII, Vilmorin 23, Hybrid 46, Strubes Dickkopf, Carstens V, Suwon 92/Omar, Nord Desprez, and Heines Peko). Only four pathotypes occurred in two or more regions. High variability was detected within Pst populations from Dagestan, Central, North-West, and West Siberia that postulated to form an intrapopulation subdivision of each of them into several subgroups. Most regional virulence groups of pathotypes were closely related, except for several small subgroups of pathotypes from West Siberia, Dagestan, North-West, and Central European regions. All Pst isolates were avirulent in lines with Yr5, Yr10, Yr15, and Yr24 genes. Virulence to Yr17 was detected for several isolates of two pathotypes, one each from the North-West and Low Volga regions. Variation in virulence frequency was observed in other differential lines

Cost of resistance to trematodes in freshwater snail populations with low clonal diversity

Abstract 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

Beta redundancy for functional ecology

International audience1. Functional beta redundancy has been recently defined as the fraction of species dissimilarity between two plots not expressed by functional dissimilarity. As such, it summarizes to what degree the compositional differences between two plots mirror their functional differences. 2. A fundamental condition to obtain an appropriate measure of functional beta redundancy is that the functional dissimilarity between the plots is always lower (or at least not higher) than the corresponding species dissimilarity. However, many of the extant measures of functional dissimilarity do not fulfill this requirement. 3. To overcome this problem, a class of tree-based indices of functional dissimilarity that conform to the above 'redundancy property' has been recently proposed. However, functional dissimilarity measures need not necessarily be based on a hierarchical representation of the species functional relationships. 4. In this paper we introduce an algorithmic index of functional dissimilarity that conforms to the redundancy property. Since it does not rely on a hierarchical species organization, the proposed index allows to calculate functional beta redundancy in a more suitable way to the non-hierarchical structure of the species functional relationships. The behavior of the proposed measure is illustrated with data on the species functional turnover along real and simulated ecological gradients

On two dissimilarity-based measures of functional beta diversity

In this paper, we propose two related versions of a dissimilarity-based measure of functional beta diversity, together with the associated tests for differences in beta diversity among different groups of samples. Both measures are based on the optimal functional matching between the species in two samples. As such, they are tightly connected to Hurlbert's seminal work on encounter-based diversity measures. The behavior of the proposed measures is illustrated with one worked example on the functional turnover of Alpine species along a successional gradient. Results show that both measures proved able to detect the functional turnover of vegetation along the chronosequence. The method, for which we provide a simple R function, further allows to evaluate the functional contribution of single sampling units to the overall beta diversity of any kind of species assemblages