ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 102, No. 3 (2015), p. 335–342
DOI 10.13080/z-a.2015.102.043

The structure of mating type, metalaxyl resistance and virulence of Phytophthora infestans isolates collected from Latvia



Potato late blight, caused by the oomycete Phytophthora infestans (Mont.) de Bary, is one of the most serious potato (Solanum tuberosum L.) diseases, causing considerable yield loss in potato production worldwide, including Latvia. At present, the data on the population characteristics of P. infestans in Latvia is sparse. Therefore, the main aim of this study was to collect new data on Latvian isolates of P. infestans, to determine the main characteristics of the pathogen, particularly mating types, metalaxyl resistance and virulence with Black’s differential set of potato genotypes containing resistance (R) genes R1–R11.

During 20102012, 181 isolates of P. infestans were collected from 23 potato fields, from 13 locations in Latvia. Out of 181 isolates tested, 52.5% were A1, 43.1% – A2 and 4.4% – self-fertile mating type. Of 116 isolates screened for resistance to metalaxyl, 25.9% were resistant, 19.8% – intermediate and 54.3% – sensitive. More than 80% of isolates were virulent to R1, R3, R4, R7, R10 and R11, while 33% or fewer isolates were virulent to R5, R8 and R9. The least frequent was virulence against R9 in 24% of isolates. Our study revealed that the Latvian population of P. infestans is diverse. The proportion of mating types and the occurrence of both A1 and A2 in the same field indicate the possibility of sexual recombination in Latvian fields. Thus, it is very important to keep the crop rotation system, to prevent soil contamination with long-living oospores. The Latvian population of P. infestans shares many similarities with other European populations, which suggests gene flow between populations.

Key words: mating type, metalaxyl resistance, potato late-blight, virulence.

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