Climate change is leading to increased occurrence of and yield losses to wheat diseases. Managing these diseases by introducing new, effective and diverse resistance genes into cultivars represents an important component of sustainable wheat production. In 2016 and 2017 a set of primary hexaploid synthetic wheat was studied under high disease pressure: powdery mildew, leaf and stem rust in Omsk; Septoria tritici and S. nodorum in Moscow. A total of 28 synthetics (19 CIMMYT synthetics and 9 Japanese synthetics) were selected as having combined resistance to at least two diseases in both years of testing. Two synthetics (entries 13 and 18) originating from crosses between winter durum wheat Ukrainka odesskaya-1530.94 and various Aegilopes taushii accessions, and four synthetics (entries 20, 21, 23 and 24) from cross between Canadian durum wheat Langdon and Ae. taushii were resistant to all four pathogens. Pathological and molecular markers evaluation of resistance suggests presence of new genes and diverse types of resistance. The novel genetic sources of disease resistance identified in this study can be successfully utilized in wheat breeding.
Northern Kazakhstan is the main zone of spring wheat cultivation where, 85 % of the cultivated area is located. There is not a single variety resistant to Septoria spot among the varieties approved for use. The frequency of epiphytoties of wheat diseases in the northern part of Kazakhstan is four cases every ten years. During the years of epiphytotic development of brown rust and Septoria spot with the dominance of a particular disease, the yield of spring wheat is reduced by 25 % or more. Knowledge of the species composition of pathogens of Septoria spot allows a more focused approach to the study and creation of varieties of wheat resistant to this disease. The aim of the research is to study the species of Septoria spot pathogens in wheat in Northern Kazakhstan. In 2018–2019, the pathogenic complex of the causative agents of wheat Septoria spot was studied. The collection of leaves affected by Septoria spot was carried out on spring wheat varieties in the steppe, forest-steppe zones of Northern Kazakhstan. The species composition of Septoria pathogens was determined from microscopic preparations from the collected samples; which were represented by three types of septorial fungi: Septoria tritici, Stagonospora nodorum, Stagonospora avenae. In the steppe and forest-steppe zones of Northern Kazakhstan, the dominant species was S. tritici followed by S. nodorum.
A b s t r a c tSeptoria tritici blotch (STB) or Stagonospora nodorum blotch (SNB) are among the most harmful and economically significant diseases of wheat in the grain growing regions of the world, especially in the countries with a temperate climate. In epiphytotic years the losses from the disease can reach 30-40 %. In Russia the diseases holds a dominant position in a pathogenic complex of fungus diseases of grain crops. In this paper we first determined the parameters of partial resistance in the cultivars of wheat (genus Triticum) from the collection of the Germplasm Resources Information Network (GRIN, USA) using the stable strains of Septoria tritici and Stagonospora nodorum pathogens. The aim of our study was to select wheat varieties with long-term resistance to blotch based on field and laboratory tests. A long-term study (2009)(2010)(2011)(2012)(2013)(2014)(2015) of the disease development on the wheat cultivars from GRIN Collection were conducted at artificial infection in infection nursery (Central region of Russia, Moscow Province). The samples studied belonged to various genetic groups. A total of 20 samples were diploids (2n = 14), 409 samples were tetraploids (2n = 28), 1688 samples were hexaploids (2n = 42), and also 397 lines derived from crossing of Triticum aestivum with Aegilotriticum were tested. The area under disease progress curve was determined, and the index of resistance (IR) was calculated. The cultivars, that characterized by slow development of the disease in the field, i.e. with high-and middle IR, were selected for laboratory studies. The plants were grown in artificial climate chambers till the 3 rd leaf fully unfolded. Pieces of leaves were inoculated by a drop of spore suspension of S. tritici (4 isolates) or St. nodorum (4 isolates), 10 replications per each variety-topathotype combination. The samples were grouped according to the latent period length and size of infectious spots. As a result, 191 samples of T. aestivum subsp. aestivum and a sample of T. aestivum subsp. spelta with a high index of resistance to the disease were selected among hexaploid wheat; 16 samples were found in tetraploid wheat, including 8 samples of T. turgidum subsp. durum, 2 samples of T. turgidum subsp. turgidum, 3 samples of T. turgidum subsp. dicoccon, 3 samples of T. timopheevii subsp. timopheevii; and 4 samples were selected from diploid wheat T. monococcum subsp. aegilopoides. Eleven lines derived from crossing of T. aestivum and Aegilotriticum sp. showed the sloweddown in the disease development. The selected hexaploid wheat cultivars were mostly from North American ecology-geographical group of T. aestivum subsp. aestivum, including 77 cultivars from the USA and 18 -from Canada (34.5 % in total). Selected tetraploid wheat samples of T. turgidum subsp. durum were from North and Central America, and those of T. turgidum subsp. turgidum, T. timopheevii subsp. timopheevii and T. turgidum subsp. dicoccon from Europe and Asia. The samples from Iraq and Hungary with a high index of blotch resist...
Mycosphaerella graminicola (anamorph Septoria tritici), the causal agent of septoria tritici blotch (STB) of wheat, is dominating species in Septoria/Stagonospora complex on crops in the main grain-producing areas of Russia. Resistance to STB may be either quantitative (horizomtal) or isolate-specific (vertical). At present 17 genes for resistance have been identified (Stb1-Stb17). The genfor-gen interaction in the «wheat-M. graminicola» pathosystem has been demonstrated by genetic analysis; therefore, the aviability of resistance genes in the host proposes the existence of specific virulence genes in the pathogen. The relative frequency of virulence genes within a geographic region may be calculated as a fraction of the isolates expressing this virulence genes from the overall number of isolates used in the study. The purpose of the present study was to estimate the virulence genes in populations of M. graminicola from different geographic regions of Russia on the basis of a genfor-gen relationship, using the cultivars with known resistance genes, i.e. Bulgaria 88 (Stb1), Oasis (Stb1), Veranopolis (Stb2), Israel 493 (Stb3), Tadinia (Stb4), CS/Synthetic 7D (Stb5), Flame (Stb6), Estanzuela Federal (Stb7), W7984 (Stb8). A total of 47 isolates from the North-Caucasian region, 66 isolates from the Central-Chernozem region, 29 isolates from the Volga region, 64 isolates from the Central region, and 34 isolates from the NorthWest region were tested under greenhouse and grows chamber conditions. The virulence was estimated on seedlings at two-leaf stage, using two parameters, the infection degree of plants and sporulation of fungus in vivo. The effectiveness of Stb-genes to each regional population of M. graminicola was revealed on the basis of the frequency of virulence genes. The regional populations of M. graminicola differed in virulence genotype, spectrum and frequency of virulence genes. The populations from south zone (the North-Caucasian, the Central-Chernozem and the Volga regions) are more virulent in comparison with the central and the northwest populations. For example, 19.2 % of isolates from the north-caucasian population and 6.0 % of isolates from the central-chernozem population have no virulence genes, while in the central and northwest populations-42.2 % and 44.1 %, respectively. Isolates from the Volga population of M. graminicola had most various combinations of virulence genes. High frequency of virulence to genes Stb1, Stb5 and Stb7 was revealed in all populations. The genes Stb2, Stb3, Stb4 have considerable effectiveness to the central, the central-chernozem and the northwest populations of M. graminicola, however it distinctly reduced concerning isolates from the North-Caucasian and the Volga regions. The genes Stb6 and Stb8 were highly effective (Stb8-absolutely effective) to all investigated Russian populations of M. graminicola and may be recommended for using in selection as sources of resistance to STB.
Genetic homogeneity of wheat crops possessing inefficient resistance genes, together with large variability in the mycopathogen virulence result in increasing losses of the harvest from fungal diseases worldwide. Therefore, the persistent long-term resistance varieties are the main element in the strategy of integrated plant protection aimed at reducing risk of environmental pollution by fungicides. Updating the set of such varieties preserving efficiency in different agricultural systems, the regional planning of their placement in crops would be more effective to provide protection against mycopathogens and to constrict the spread of new virulence genes. We first performed a comprehensive assessment of resistance to major fungal pathogens for winter wheat varieties of different ecogeographical and breeding origin from the VIR World Collection (N. I. Vavilov All-Russian Institute of Plant Genetic Resources, St. Petersburg), the collections of Krasnodar Research Institute of Agriculture (KNIISH, South of Russia) and Nemchinovka Moscow Research Institute of Agriculture (MRIA, Central Russia). The goal was to select the donors of resistance to adverse biotic factors, including the most harmful diseases: brown rust (Puccinia triticina Eriks.), stem rust (P. graminis Pers.), powdery mildew (Blumeria graminis (DC.) Speer f. sp. tritici Marchal.), Septoria (Septoria tritici Rob. et Desm. and Stagonospora nodorum Berk.) from the collections of VIR, KNIISH and MRIA. Among 158 winter wheat cultivars the field resistance to leaf rust has been showed in 8.9 %, to stem rust in 5.1 %, and to Septoria spp. in 1.3 %. No wheat cultivars were resistant to powdery mildew. Evaluation of wheat seedling resistance to leaf rust in a climatic chambers allowed to identify samples with adult and race-specific resistance. The Ukrainian varieties differed geographically in resistance to the leaf rust. The varieties resistant to two or more pathogens were the most important. Cultivars Junona, Tanya (KNIISH), Bogdanka (derived from Belgorod region.) have been possessed the resistance to leaf and stem rust. Cultivars Borvij, Zagrava odes'ka (Ukraine), Catalus (Germany) were partial resistant to leaf rust and moderate susceptible to Septoria spp. Cultivars Gyrmyzy Gjul' 1 (Azerbaijan), Catalus (Germany) were important due to their combined resistance to Septoria tritici and Stagonospora nodorum. KS 93450 (USA) has combined partial resistance to leaf rust, moderate susceptibility to Septoria spp. and stem rust resistance. These samples can be further used in breeding.
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