Highly Diverse Phytophthora infestans Populations Infecting Potato Crops in Pskov Region, North-West Russia

There is limited understanding of the genetic variability in Phytophthora infestans in the major potato cultivation region of north-western Russia, where potato is grown primarily by small households with limited chemical treatment of late blight. In this study, the mating type, sensitivity to metalaxyl, and genotype and population genetic diversity (based on 12 simple sequence repeat (SSR) markers) of 238 isolates of P. infestans from the Pskov region during the years 2010–2013 were characterized. The aim was to examine the population structure, phenotypic and genotypic diversity, and the prevalent reproductive mode of P. infestans, as well as the influence of the location, time, and agricultural management practices on the pathogen population. The frequency of the A2 mating was stable over the four seasons and ranged from 33 to 48% of the sampled population. Both mating types occurred simultaneously in 90% of studied fields, suggesting the presence of sexual reproduction and oospore production in P. infestans in the Pskov region. Metalaxyl-sensitive isolates prevailed in all four years (72%), however, significantly fewer sensitive isolates were found in samples from large-scale conventional fields. A total of 50 alleles were detected in the 141 P. infestans isolates analyzed for genetic diversity. Amongst the 83 SSR multilocus genotypes (MLGs) detected, 65% were unique and the number of MLGs varied between locations from 3 to 20. These results, together with the high genotypic diversity observed in all the locations and the lack of significance of linkage disequilibrium, suggest that sexual recombination is likely responsible for the unique MLGs and the high genetic diversity found in the Pskov region population, resembling those of north-eastern European populations

Cultivation technology influences the occurrence of potato early blight (Alternaria solani) in an organic farming system

Abstract Nowadays, organically produced products have become more popular than ever and interest in them is still growing fast. The early blight causal pathogen Alternaria solani has not been considered a great threat to potato in northern climate conditions in the past and has not been routinely sprayed against. During our study early blight was evaluated in 2010 and 2011 on the plants of a potato cultivar 'Reet' in an organic farming experiment. In our study, both growing seasons were very favourable for early blight development. Significant differences between the two cultivation technologies were found (F 1,12 = 4.84, p = 0.048). In 2010, the area under disease progress curve (AUDPC) value was 303 on cover crop (CC) plots and 990 on CC + M (manure) plots that is three times higher, whereas in 2011, the AUDPC value was 967 on CC plots and 1195 on CC + M plots. Our results confirm that potato early blight has become a serious problem in North-East European organic potato fields and thus susceptible potato cultivars cannot be recommended for growing in an organic farming system. However, it is possible to influence the development severity of early blight by selecting the proper growing technology. Since, in the changing climate conditions and in susceptible cultivars, early blight is a potato disease that can cause early defoliation of plants and crop death, there is a need for resistant potato cultivars

Evaluation of late blight resistance on potato varietis importe to Estonia

Kartuli-lehemädanik, mida põhjustab Phytophthora infestans, on üks kõige enam kahju tekitav kartulihaigus juba üle pooleteise sajandi nii Eestis kui ka mujal Euroopas. Lehemädanik võib soodsa ilmastiku korral lühikese ajaga hävitada taime lehestiku, põhjustades seega suure saagikao. Eestis võib haigusest tulenevalt saagikadu ulatuda 20–25%, töötlemata põldudel isegi rohkem. Ilma kartuli-lehemädaniku kontrolli all hoidmata ei ole võimalik saada kõrget ja kvaliteetset saaki. Kartulikasvatajatel on üha suurem huvi kasvatada Lääne-Euroopast imporditavaid kartulisorte, mis on aga Eesti oludes osutunud suhteliselt lehemädaniku õrnadeks. Einola tallu rajatud katse eesmärgiks oli leida Hollandi aretusfirma Agrico 16 kartulisordi hulgast kõige lehemädanikukindlamad ja suurima saagikusega sordid Eesti oludesse ja võrrelda neid Eestis aretatud standard sortidega. Saadud tulemuste põhjal antakse soovitusi kohalikele kartulikasvatajatele. Suurima saagikusega ja ka kõige lehemädanikukindlamateks sortideks osutusid varajane sort ’Evolution’, keskvalmiv sort ’Toluca’ ja hiline sort ’Anti’, mida soovitaks ka kartulikasvatajatele. Saagi andmetest lähtuvalt soovitaks veel sorte ’Maret’, ’Ambition’ ja ’Manitou’. Kõige lehemädaniku kindlamaks sordiks osutus sort ’Toluca’ (haiguskindlus 8,8 palli), mis on tunnistatud Hollandis resistentseks. Ühe aasta katsetulemuste põhjal võib järeldada, et enamus sorte osutus lehemädanikule väga vastuvõtlikuks või vastuvõtlikuks ja neid sorte ei saa kasvatada Eesti tingimustes ilma lehemädaniku keemilist tõrjet teostamata ning ei ole võimalik tõrjekulude kokku hoidmiseks tõrje intervalli pikendada.Potato late blight causing pathogen Phytophthora infestans is one of the most serious and economically important pathogens in potato fields worldwide, including Estonia. Under favourable conditions it can destroy the whole potato haulm and cause a considerable yield loss. In Estonia, the average yield loss due to late blight can reach 20-25% and in untreated fields even more. Without control of potato late blight is not possible to achieve high highquality crop yield. Potato growers in Estonia are more interested to grow western European potato varieties and their concern is based on quality and crop yield. The main aim of research was to find among breeding company Agrico varieties most susceptible varieties to late blight and high yield in Estonian conditions and comparable these with Estonian breeding company varieties. Based on this information suggest potato varieties to growers. In the trial at the Einola Farm 16 Netherlands potato varieties and 4 Estonian varieties included. The trial results showed biggest yield and high resistance on early variety ‘Evolution’, medium late variety ‘Toluca’ and late variety ‘Anti’, which are highly recommended to potato growers in Estonia. Based on trial results and high crop yield we suggest also varieties ‘Maret’, ’Ambition’ ja ’Manitou’. Early and early medium varieties are too susceptible for growing without chemical control against late blight. The most resistant variety was Toluca (foliar blight estimated mean value 8,8), which is immune to foliar blight in its land of origin. Based on one year data we can conclude that most of the tested varieties are too susceptible to late blight to be grown without chemical control against this pathogen in Estonian condition

Late blight resistance of potato varieties and impact to crop yield

Kartuli-lehemädanik, mida põhjustab Phytophthora infestans, on üks kõige enam kahju tekitav kartulihaigus juba üle pooleteise sajandi nii Eestis kui ka mujal Euroopas. Lehemädanik võib soodsa ilmastiku korral lühikese ajaga hävitada taime lehestiku, põhjustades seega suure saagikao. Eestis võib haigusest tulenevalt saagikadu ulatuda 20-25%, töötlemata põldudel isegi rohkem. Ilma kartuli-lehemädaniku kontrolli all hoidmata ei ole võimalik saada kõrget ja kvaliteetset saaki. Kartulikasvatajatel on üha suurem huvi kasvatada Lääne-Euroopast imporditavaid kartulisorte, mis on aga Eesti oludes osutunud suhteliselt lehemädaniku õrnadeks. Einola tallu rajatud katse eesmärgiks oli leida Hollandi aretusfirma Agrico 14 kartulisordi ja 2 aretise hulgast kõige lehemädanikukindlamad ja suurima saagikusega sordid Eesti oludesse ning saadud tulemuste põhjal anda soovitusi kartulikasvatajatele. Suurima saagikusega sortideks osutusid hilisemapoolsed kartulisordid, kuna lehemädanik lööbis suhteliselt hilja (1 august) ja pikema kasvuperioodiga sordid suutsid efektiivselt ära kasutada augusti lõpus ning septembri algul tulnud sademeid. Kombineerides lehemädaniku vaatlusandmeid ja saagiandmeid, siis soovitaks ühe aasta katse põhjal kartulikasvatajatele hilisemapoolseid suurima saagikusega sorte ’Ambition’, ’Fontane’, Excellent’, ’Manitou’ ja ‘Red Baron’. Kõige lehemädaniku kindlamaks sordiks osutus sort ’Toluca’ (haiguskindlus 7,2 palli), mis on tunnistatud Hollandis resistentseks. Ühe aasta katsetulemuste põhjal võib järeldada, et enamus sorte osutus lehemädanikule väga vastuvõtlikuks või vastuvõtlikuks ja neid sorte ei saa kasvatada Eesti tingimustes ilma lehemädaniku keemilist tõrjet teostamata ning ei ole võimalik tõrjekulude kokku hoidmiseks tõrje intervalli pikendada.Potato late blight causing pathogen Phytophthora infestans is one of the most serious and economically important pathogens in potato fields worldwide, including Estonia. Under favourable conditions it can destroy the whole potato haulm and cause a considerable yield loss. In Estonia, the average yield loss due to late blight can reach 20-25% and in untreated fields even more. Without control of potato late blight is not possible to achieve high high-quality crop yield. Potato growers in Estonia are more interested to grow western European potato varieties and their concern is based on quality and crop yield. The main aim of research was to find among breeding company Agrico varieties most susceptible varieties to late blight and high yield in Estonian conditions and based on this information suggest potato varieties to growers. In the trial at the Einola Farm 14 potato varieties and 2 breeding lines were included. The trial results showed bigger yield on medium late varieties and were influenced on the length of growing period and larger amounts of precipitations on late August and the beginning of September. Based on results of late blight observation trial and crop yield we suggest medium late varieties ‘Ambition’, ‘Fontane’, ‘Excellent’, ‘Manitou’ and ‘Red Baron’. Early and early medium varieties are too susceptible for growing without chemical control against late blight. The most resistant variety was Toluca (foliar blight estimated mean value 7.2), which is immune to foliar blight in its land of origin. Based on one year data we can conclude that most of the tested varieties are too susceptible to late blight to be grown without chemical control against this pathogen in Estonian conditions

High Temporal Variability in Late Blight Pathogen Diversity, Virulence, and Fungicide Resistance in Potato Breeding Fields: Results from a Long-Term Monitoring Study

Long-term site-specific studies describing changes in the phenotypic variability of Phytophthora infestans populations allow quantitative predictions of pathogen spread and possible outbreaks of epidemics, and provide key input for regional resistance breeding programs. Late blight samples were collected from potato (Solanum tuberosum) breeding fields in Estonia during a twelve-year study period between 2001 and 2014. In total, 207 isolates were assessed for mating type and 235 isolates for metalaxyl resistance and 251 isolates for virulence factors. The frequency of mating types strongly fluctuated across the years, whereas the later period of 2010–2014 was dominated by the A2 mating. Despite fluctuations, both mating types were recorded in the same fields in most years, indicating sustained sexual reproduction of P. infestans with oospore production. Metalaxyl-resistant and intermediately resistant strains dominated in the first years of study, but with the progression of the study, metalaxyl-sensitive isolates became dominant, reaching up to 88%. Racial diversity, characterized by normalized Shannon diversity index decreased in time, varying from 1.00 in 2003 to 0.43 in 2013. The frequency of several virulence factors changed in a time-dependent manner, with R2 increasing and R6, R8, and R9 decreasing in time. Potato cultivar resistance background did not influence the frequency of P. infestans mating type, response to metalaxyl, and racial diversity. However, the diversity index decreased in time among isolates collected from resistant and susceptible cultivars, and remained at a high level in moderately resistant cultivars. These data demonstrate major time-dependent changes in racial diversity, fungicide resistance, and virulence factors in P. infestans, consistent with alterations in the control strategies and popularity of potato cultivars with different resistance

Alternaria Black Spot (Alternaria brassicae) Infection Severity on Cruciferous Oilseed Crops

The increase in the cultivation area of cruciferous oilseed crops and the use of short crop rotation has resulted in the enhanced spread of several major pests in Northern latitudes. There is currently limited information about incidence and severity of Alternaria black spot disease (Alternaria brassicae) on the main oilseed crop, spring oilseed rape (Brassica napus), in the Northern Baltics. Thus, spring oilseed rape and five alternative cruciferous oilseed crops were selected and their resistance to black spot disease was evaluated in field conditions during two growing seasons. We hypothesized that spring oilseed rape is more susceptible to Alternaria black spot disease than other alternative cruciferous oilseed crops. Both growing seasons were warmer and drier compared to the long-term average, and were thus suitable for A. brassicae development and assessments. In both years, incidence of Alternaria black spot infection was recorded on all cruciferous species, yet the disease development differed considerably among the crops. During both growing seasons, black mustard (B. nigra) plants were the most infected. Based on our observations during warm growing seasons we conclude that alternative oilseed crops such as Sinapis alba, Eruca sativa and Raphanus sativus are more resistant to the Alternaria black spot infection than the traditional oilseed crops and thus, possess a great potential to grow with limited chemical disease control in Northern Baltic conditions

The variability of Phytophthora infestans isolates collected from Estonian islands in the Baltic Sea

Knowledge of a pathogen's genetic variability and population structure is of benefit to effective disease management. In this study, 193 isolates of Phytophthora infestans collected from three Estonian islands, were characterized over three years using SSRs marker data complemented by information on their mating type and resistance to metalaxyl. In combination with SSR marker data from samples in the neighbouring Pskov region of north west Russia, the impact of regional and landscape structure on the level of genetic exchange was also examined. Among the Estonian islands 111 P. infestans isolates, forty-nine alleles were detected among twelve SSR loci, and 59 SSR multilocus genotypes (MLGs) were found, of which 64% were unique. The genetic variation was higher among years than that among islands, as revealed by AMOVA. The frequency of metalaxyl-resistant isolates increased from 9% in 2012 to 30% in 2014, and metalaxyl resistant was most frequent among A1 isolates. The test for isolation by distance among the studied regions was not significant, and coupled with the absence of genetic differentiation revealed gene flow, and the absence of local adaptation. The data are consistent with a sexual population in which diversity is driven by an annual germination of soil-borne oospores. The absence of shared genotypes over the years has important implications when it comes to the management of disease. Such population diversity can make it difficult to predict the nature of the outbreak in the coming year as the genetic makeup are different for each year.</p

Cultivation technology influences the occurrence of potato early blight (Alternaria solani) in an organic farming system

Nowadays, organically produced products have become more popular than ever and interest in them is still growing fast. The early blight causal pathogen Alternaria solani has not been considered a great threat to potato in northern climate conditions in the past and has not been routinely sprayed against. During our study early blight was evaluated in 2010 and 2011 on the plants of a potato cultivar ‘Reet’ in an organic farming experiment. In our study, both growing seasons were very favourable for early blight development. Significant differences between the two cultivation technologies were found (F1,12 = 4.84, p = 0.048). In 2010, the area under disease progress curve (AUDPC) value was 303 on cover crop (CC) plots and 990 on CC + M (manure) plots that is three times higher, whereas in 2011, the AUDPC value was 967 on CC plots and 1195 on CC + M plots. Our results confirm that potato early blight has become a serious problem in North-East European organic potato fields and thus susceptible potato cultivars cannot be recommended for growing in an organic farming system. However, it is possible to influence the development severity of early blight by selecting the proper growing technology. Since, in the changing climate conditions and in susceptible cultivars, early blight is a potato disease that can cause early defoliation of plants and crop death, there is a need for resistant potato cultivars