Leaf rust represents the major threat to wheat production in Russia and Ukraine. It has been present for many years and epidemics of the pathogen occur in different regions on both winter and spring wheat. In some regions there is evidence of more frequent epidemics, probably due to higher precipitation as a result of climate change. There is evidence that the virulence of the leaf rust population in Ukraine and European Russia and on winter wheat and spring wheat is similar. The pathogen population structure in Western Siberia is also similar to the European part, although there are some significant differences based on the genes employed in different regions. Ukrainian wheat breeders mostly rely on major resistance genes from wide crosses and have succeeded in developing resistant varieties. The North Caucasus winter wheat breeding programs apply the strategy of deploying varieties with different types of resistance and genes. This approach resulted in decreased leaf rust incidence in the region. Genes Lr23 and Lr19 deployed in spring wheat in the Volga region were rapidly overcome by the pathogen. There are continuing efforts to incorporate resistance from wild species. The first spring wheat leaf rust resistant varieties released in Western Siberia possessed gene LrTR which protected the crop for 10-15 years, but was eventually broken in 2007. Slow rusting is being utilized in several breeding programs in Russia and Ukraine, but has not become a major strategy.
The virulence frequency of 750 wheat powdery mildew isolates of wheat genotypes, carrying 23 Pm-genes and gene combinations, was studied over ten consecutive years from 2004 to 2013. Seventy-eight previously known and 39 new pathotypes were identified during this period. The results indicate that the majority of Pm-genes have high level of virulence. Sixty to ninety percent of the isolates were virulent to Pm6, Pm8, Pm8+11, Pm2+4b+8, Pm3g, Pm10+15, Pm10+14+15. The virulence frequency was variable for Pm1a, Pm2, Pm3a, Pm3b, Pm3c, Pm5, Pm7 genes and reached high level in certain years. The virulence frequency to genes Pm20, Pm37, Pm4a+ and to gene combination with Pm3c+5a+35 and breeding lines CN240/06, CN98/06 and CN158/06 ranged from 1 to 8%. Bread wheat lines CN240/06, CN98/06 and CN158/06, derived from interspecific crosses, proved to be highly resistant to powdery mildew.
Leaf rust is the most widespread and frequently occurring fungal disease of wheat (Triticum aestivum L.) in Ukraine and worldwide. The information about the effectiveness of Lr-genes and also the consequent monitoring of virulence dynamics is necessary for the successful wheat breeding for leaf rust resistance. In 2013-2014 pathotype composition and virulence analysis was studied both on the standard differential set and on the North American System of Nomenclature. According to the standard differential set, 12 phenotypes were identified, of which the most common were 77 (75%) and 144 (6%). A total of 40 phenotypes were identified on the North American Nomenclature. Phenotypes TGTT (24%) and TJTT (8%) were the most frequent, TRTT (1.5%) and TSTT (1.5%) were within the broadest spectrum of virulence among the isolates found in the south of Ukraine. For virulence analysis we used wheat lines of 'Thatcher' that are near-isogenic for 24 leaf rust resistance genes and additionally four cultivars/lines. No virulence to Lr19 was found, whereas increasing virulence to Lr9 was detected (13%). Low frequency of virulence was observed to Lr29 (11%) and Lr47 (21%), high level of virulence was detected to other genes. The effectiveness of 53 known Lr-genes was studied at the seedling and the adult plant stages. Most of them were not effective against leaf rust. Genes Lr9, Lr19, Lr29, and Lr47 were highly effective both at the seedling stage and at adult plant stage. Genes Lr24, Lr42, Lr50, Lr51, and Lr56 were effective only at the adult plant stage.
For the present study, samples of cleistothecia were collected in Central Lithuania and Southern Ukraine. To characterize the virulence, complexity and diversity of powdery mildew (Blumeria graminis f. sp. tritici) populations, 80 isolates were derived from single ascospores, 40 isolates from each population. Pathotype analysis was conducted on 16 differentials with known Pm genes. According to the proposed nomenclature, 32 pathotypes were identified in the Lithuanian powdery mildew population and 30-in the Ukrainian population. The most frequent phenotype in Lithuania was NGDE (7.5%), and in Ukraine it was NGKE (15%). The Ukrainian powdery mildew population was more complex and contained more virulence genes per isolate. The virulence test was carried out by inoculation on detached leaves of 26 common wheat (Triticum aestivum L.) differentials with known Pm genes and 12 resistant winter wheat breeding lines and cultivars. The frequencies of virulence to these differentials ranged from 0% to 100%, and most of them had high level of virulence. No virulence was found to Pm20 and Pm25+3a genes, cultivar 'Lastivka odeska' and breeding lines CN 89/16 and PI 170911 in both populations, whereas the frequencies of virulence were more than 50% to Pm1a,
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