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Ecological risks associated with chemical pesticides encourage application of biopesticides and integrated pest management. The study compared efficiency of the Manfil fungicide and Agat-25K biopreparation (single or combined with the ExelGrow biostimulator) against the late (LB) and early (EB) blights of potato. Field experiments were conducted with three potato cultivars (Arizona, Vektor, Aluett) of different resistance levels to the LB and EB diseases. Leaf blight development was registered as LB (Arizona), LB+EB (Vektor), and EB (Aluett). Agat25K delayed LB development under epiphytotic conditions on the susceptible cv. Arizona (biological efficiency 39%), though was inferior to Manfil (62%). On the contrary, for cv. Aluett, Agat-25K showed more significant EB suppression than Manfil (96 vs. 83%). Compared to the control, the yield increase of cv. Arizona was 15.8 t/ha for Agat-25K and 25.4 t/ha for Manfil. Tuber marketability increased by 28 and 13% for Agat-25K and Manfil, respectively. For moderately resistant and resistant cultivars (Vektor, Aluett), Agat-25K provided the highest yield increase compared to Manfil (19.1 vs. 16.7 t/ha for Vektor and 4.5 vs. 1.4 t/ha for Aluett, respectively), while the tuber marketability increased by 15% (Vektor) and 18% (Aluett). Agat-25K can be recommended for use on moderately-resistant cultivars under sporadic LB epiphytoties and for the EB control. ExelGrow application with Manfil and Agat-25K was first shown to improve their biological efficiency on moderately LB-resistant and LB-resistant cultivars (up to 12%).

The oomycete Phytophthora infestans (Mont.) de Bary is a causative agent of the most harmful potato disease, late blight. The pathogenicity of P. infestans is associated with (a)virulence genes (Avr genes). Changes in the composition and nucleotide sequence of these genes lead to the emergence of new races of the pathogen, which affect potato varieties previously considered resistant. Therefore, to successfully combat late blight, it is important to study polymorphisms in Avr genes in populations of this pathogen. We conducted a large‐scale molecular and phytopathological study of P. infestans strains collected in European Russia. In this study, polymorphisms of 11 Avr genes were analysed using SSCP analysis and sequencing. The genes included Avr1, Avr2, Avr2‐like, Avr3a, Avr3b, Avr4, Avr8, Avr‐Smira1, Avr‐blb1, Avr‐blb2 and Avr‐vnt1. As a result, the allelic composition of Avr genes was studied and new alleles unique to Russia were identified in Russian populations of P. infestans for all studied Avr genes, with the exception of Avr4 and Avr8. The vast majority of the Avr1, Avr2‐like, Avr3a, Avr4, Avr‐vnt1 and Avr‐Smira1 gene sequences correspond to known virulence variants of these genes that avoid recognition by the corresponding potato resistance genes. The Avr‐blb2 gene was represented by approximately equal amounts of virulent and avirulent variants. Predominantly avirulent variants were found for the Avr‐blb1 gene. The Avr2, Avr3b and Avr8 genes were represented only by avirulent variants. Summarising the results of our study, we can conclude that the populations of the European territory of Russia differ from the populations of Europe and the USA in the allelic composition of virulence genes. We failed to detect a dominant clonal lineage in the territory of Russia, and the Russian population of P. infestans is highly diverse. [ABSTRACT FROM AUTHOR]

In recent years, skin blemish diseases of potato (including black dot (BD) caused by Colletotricum coccodes) have begun to be important for global potato marketing, since consumers often reject tubers with an imperfect appearance, which results in financial losses caused by the disposal of unwanted potatoes. Like for many non-fatal plant diseases, BD severity may depend on the immune status of plants influenced by other infectious agents. Using a set of 98 potato cultivars differing in their late blight (LB) resistance, we examined the correlation between the intensity of their infection with LB determined by their LB resistance and the occurrence of the BD disease under field conditions with a high background level of both diseases. Using LB-susceptible (Arizona) and moderately susceptible (Sante) cultivars, we also evaluated the effect of a crop protection against LB on BD development under the same field conditions. A strong negative correlation (r = −0.81, p < 0.05) between the LB resistance and the BD occurrence has been revealed. An experiment using the two cultivars, chemically protected against LB, showed a significant reduction in BD occurrence of 30% (cv. Arizona) and 20% (cv. Sante) compared to the untreated controls; the total yield and marketability of potatoes increased by 103.6 and 62.5% for cv. Arizona and by 65.9 and 43.8% for cv. Sante. The reduction in the LB affection of potato is one of the key factors improving the immune status of potato cultivars in relation to BD infection, so methods of LB protection should be included in a complex approach to BD control. [ABSTRACT FROM AUTHOR]

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A coiled coil-nucleotide binding site-leucine-rich repeat gene RB/Rpi-blb1 isolated from Solanum bulbocastanum confers broad-spectrum resistance to Phytophthora infestans and is currently employed in potato breeding for durable late blight (LB) resistance. RB homologues were reported in several Solanum species; some of them retained defence function. Here, we report additional evidence on RB-like sequences in 21 Solanum species of the section Petota. The panel of Solanum species was screened with three RB-related PCR markers. RB-like sequences were found in every tested Solanum accession, suggesting universal distribution of RB structural homologues among Solanum genomes, while locus-specific RB-629 was found only in 15 species. Phylogenetic analysis of RB-629 sequences suggested a highly conservative pattern of polymorphisms that was neither species- nor series-specific. Apparently, duplication and evolution of RB-like loci preceded Solanum speciation. Marker presence and particular haplotypes were not immediately associated with high LB resistance. [ABSTRACT FROM AUTHOR]