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Pyrenophora tritici-repentis is a phytopathogenic fungus, which forms specific phytotoxins encoded by the ToxA and ToxB genes. The aim of the study was to identify the genetic nuclear polymorphism on the ToxA and ToxB genes as evidence of the heterokaryotic state of P. tritici-repentis strains. The novelty of the study was evaluation of the proportion of nuclei with the ToxA or ToxB gene relative to the total pool of nuclei with the reference gene Act1 by quantitative PCR for the detection of heterokaryons. Twenty-one P. tritici-repentis strains from three geographical populations, as well as mitotic (conidial) and meiotic generations of individual strains (103 subclones), were analyzed in the study. The proportion of nuclei with the ToxA gene in 70% of P. tritici-repentis ToxA+ strains from the Kazakhstan population was in the range of 0.24–0.65, indicating their heterokaryotic state. In the Greek population, 20% of P. tritici-repentis ToxB+ strains characterized by the proportion of nuclei with the ToxB gene much more than 1 were detected, while at least 40% of the strains were also heterokaryotic. Probably the proportion of nuclei with effector genes is a genetically inherited trait. The low polymorphism of the proportion of nuclei with effector genes among the mitotic generation was revealed. At the same time, a broader variability of the proportion of nuclei with ToxA among the meiotic generation was found. The functional role of nuclear polymorphism for the adaptation of P. tritici-repentis isolates in the population requires further study. [ABSTRACT FROM AUTHOR]

For the first time, relative expression levels of the ToxA effector gene and PtrPf2 transcription factor gene in vitro were used to characterize the collection of isolates of the causative agent of tan spot of wheat, Pyrenophora tritici-repentis, from geographically distant populations. It was demonstrated that two groups of isolates, from Kazakhstan (Almaty oblast) and Russia (Krasnodar krai), differed in the levels of genetic diversity. The group of Krasnodar isolates was more heterogenous in expression levels of both genes. In Krasnodar isolates, positive correlation between the expression levels of examined genes was revealed (r = 0.96, p < 0.001). The isolate groups were statistically significantly different in the PtrPf2 expression levels (p = 0.002). According to preliminary data, high virulence of Kazakhstan isolates was associated with high expression levels of the PtrPf2 transcription factor gene in these isolates. A supposition on the existence of association between the PtrPf2 expression level in vitro and the ability of isolates to induce necrosis on the leaves of a susceptible cultivar is made. [ABSTRACT FROM AUTHOR]

Data on content of 90Sr, 137Cs, 239,240Pu and 3H in water of the Tobol–Irtysh part of the Techa–Iset–Tobol–Irtysh–Ob river system (through which the “Mayak” PA radioactive wastes are transported) are presented and discussed. The data were received in 2004–2005 under the ISTC project on radioecological monitoring of the Tobol and Irtysh rivers. Monthly observations of 137Cs, 90Sr and 3H content in water in the area of the Tobol and Irtysh confluence have been conducted starting from May 2004. To obtain information on the investigated river system as a whole, the radioecological survey of the Tobol and Irtysh rivers at the section from the mouth of the Iset River to the confluence with the Ob River was carried out in 2004. It is shown that the impact of “Mayak” PA waste transport by 90Sr is distinctly traced as far as the area of the Irtysh and Ob confluence. [Copyright &y& Elsevier]