RESUMEN
Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a reemerging disease that caused severe epidemics in northern Kazakhstan and western Siberia in the period of 2015 to 2019. We analyzed 51 stem rust samples collected between 2015 and 2017 in five provinces in Kazakhstan. A total of 112 Pgt races were identified from 208 single-pustule isolates. These races are phenotypically and genotypically diverse, and most of them are likely of sexual origin. No differentiation of phenotypes and single-nucleotide polymorphism genotypes was observed between isolates from Akmola and North Kazakhstan provinces, supporting the idea of a wide dispersal of inoculum in the northern regions of the country. Similarities in virulence profiles with Pgt races previously reported in Siberia, Russia, suggest that northern Kazakhstan and western Siberia constitute a single stem rust epidemiological region. In addition to the races of sexual origin, six races reported in Europe, the Caucasus, and East Africa were detected in Kazakhstan, indicating that this epidemiological region is not isolated, and spore inflow from the west occurs. Virulence alone or in combination to several genes effective against the Ug99 race group was detected, including novel virulence on Sr32 + Sr40 and Sr47. The occurrence of a highly diverse Pgt population with virulence to an important group of Sr genes demonstrated the importance of the pathogen's sexual cycle in generating new and potentially damaging virulence combinations.
Asunto(s)
Basidiomycota , Enfermedades de las Plantas , Virulencia , Enfermedades de las Plantas/genética , Kazajstán , Basidiomycota/genéticaRESUMEN
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. tritici- repentis 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, KR11-9025, KR12-07, GN-68/2003). The results of this study are of interest in wheat breeding programs for tan spot resistance.