Листовые болезни яровой пшеницы-бурая ржавчина (возбудитель-Puccinia triticina), желтая пятнистость (пиренофороз) (Pyrenophora tritici-repentis) и темно-бурая пятнистость (Сochliobolus sativus = Bipolaris sorokiniana)-относятся к группе распространенных и потенциально опасных болезней в западноазиатских регионах России и Северном Казахстане. Для обоснования стратегий генетической защиты пшеницы необходимы популяционные исследования фитопатогенов. Цель работыхарактеристика структуры популяций возбудителей бурой ржавчины и желтой пятнистости яровой пшеницы по признакам вирулентности и оценка распространенности возбудителя темно-бурой пятнистости в западноазиатских регионах Российской Федерации и Северном Казахстане в 2017 г. Источником инфекционного материала служили пораженные бурой ржавчиной и пятнистостями листья образцов яровой пше ницы, собранные в Челябинской и Омской областях и Северном Казахстане. Анализ вирулентности 109 изолятов P. triticina на 20 линиях-дифференциаторах показал, что все изученные монопустульные изоляты были авирулентны к ТсLr24. Изоляты, вирулентные к ТсLr19, выявлены только в челябинской популяции. Частоты вирулентных изолятов к ТсLr2a, ТсLr2b, ТсLr2c, ТсLr11, ТсLr15, ТсLr16, ТсLr20 и ТсLr26 были выше в омской и североказахстанской популяциях, а к ТсLr9-в челябинской. При использовании 20 ТсLr-ли ний определено 27 фенотипов вирулентности P.
Pyrenophora tritici-repentis is a causative agent of tan spot in wheat. In recent years, there has been an increasing spread and harmfulness of wheat tan spot. The aim of the research was to study the racial composition of the P. tritici-repentis population in the Republic of Kazakhstan. A collection of 30 common wheat accessions, including promising lines and cultivars from Kazakhstan and CIMMYT–ICARDA, was assessed for resistance to P. triticirepentis in a greenhouse and characterized using the Xfcp623 molecular marker, diagnostic for the Tsn1 gene. Monosporic isolates of P. tritici-repentis isolated from the southeastern region were assigned to certain races based on the manifestation of symptoms of necrosis/chlorosis on standard differentials (Glenlea, 6B662, 6B365). Five races of P. tritici-repentis have been identified, including races 1, 2, 3, 7 and 8. It has been shown that races 1 and 8 of P. tritici-repentis are dominant. As a result of the analysis of the frequency of occurrence of the P. tritici-repentis races, it was found that race 1 (50 %) producing Ptr ToxA and Ptr ToxB and race 8 (35 %) producing Ptr ToxA, Ptr ToxB and Ptr ToxC turned out to be dominant. From a practical point of view, of greatest interest are 16 wheat samples, which demonstrated resistance to race 1 and confirmed insensitivity to Ptr ToxA in a molecular screening. These include eight Kazakhstani (4_PSI, 10204_2_KSI, 10204_3_KSI, 10205_2_KSI, 10205_3_KSI, 605_SP2, 632_SP2, Dana) and seven foreign lines (KR11-20, KR11-03, KR11-9014, 11KR-13, KR12-9025, KR12-07, GN-68/2003). The results of this study are of interest in wheat breeding programs for tan spot resistance.
Tan spot caused by Pyrenophora tritici-repentis (Died.) Drechsler, in recent years, occupies an increasingly large area on the territory of Russia. Due to the wide distribution and economic significance of this disease, the search for resistant plants to the pathogen is relevant. This paper presents the results of a field assessment for 2017–2019 of 34 regionally distributed winter wheat varieties of Russian selection for resistance to P. tritici-repentis in the North Caucasus region of Russia. Field resistance - the development of the disease up to 30% against the background of artificial infection for three years was shown by 20.5% of the studied varieties. Wheat varieties were assessed for resistance to isolates of tan spot identified as races 1, 3, and 4 in the greenhouse at the seedling stage. The number of resistant accessions for each race was different and ranged from 12 to 20. The 12 varieties showed resistance to race 1, 14 varieties to race 3, 20 varieties to race 4. This research showed that the resistance to tan spot of studied varieties was race-specific. A functional allele of the susceptibility gene Tsn1 to P. tritici-repentis isolates, producing the toxin Ptr ToxA, was diagnosed by PCR method. Of the analyzed 34 varieties, 13 had a dominant allele of the Tsn1 (Tsn1 + ), and 21 had a recessive allele in the tsn1tsn1 homozygous state. All Tsn1 + varieties, and most varieties with recessive alleles tsn1tsn1 , were susceptible to tan spot in the field. Varieties Dolya, Gurt, Lebed and Sila, which showed field resistance, had the tsn1tsn1 genotype. The expected reaction of varieties with different allelic composition of the Tsn1 gene to inoculation with the isolate of race 1, according to the generally accepted model of “gene-to-gene” interaction, did not coincide with that observed in reality, which confirms the results obtained by other authors. Research results demonstrate the effect of weather conditions on the susceptibility of wheat varieties to tan spot. In years with higher humidity and higher average air temperatures, the susceptibility response to the disease was observed in more varieties than in drier years. The studies show that the main part (79.5%) of winter wheat varieties of Russian selection widely zoned in the North Caucasus region of Russia are susceptible to P. tritici-repentis . Varieties that have been resistant to the pathogen in the adult phase in the field for three years and to the pathogen races in which the recessive allele of the tsn1 gene has been identified may be of interest as sources of resistance for developing new disease-resistant varieties.
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