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

The impact of isolation on Estonian populations of Phytophthora infestans

Phytophthora perekonda kuulub enam kui 60 liiki olulisi taimehaiguste tekitajaid, millest Phytophthora infestans on üks enim uuritud patogeen ülemaailmselt. Lehemädanikutekitaja patogeen, mis on seenetaoline mikroorganism pani aluse fütopatoloogiale kui teadusele, ning tema arenemist ja levikut uuritakse siiani. Euroopas ja s.h. ka Eestis levib patogeeni „uus“ populatsioon, omades kahte paarumistüüpi A1 ja A2 ning paljunedes suguliselt moodustades oospoore. Ühtlasi on muutunud ka patogeeni ökoloogia, epidemioloogia, virulentsus, fungitsiidiresistentsus ning vastupidavus ebasoodsatele ilmastikuoludele. Varasemalt on uuritud P. infestans populatsioone ainult mandri Eestis. Saartelt alustati lehemädaniku isolaatide kogumisega 2012. aastal, mistõttu ei olnud enne käesolevat tööd uuritud, millised populatsioonid seal levivad. Antud töö eesmärk oli uurida kas saarte populatsioonid sarnanevad mandri populatsioonidega või mitte. Kokku koguti 2012. aastal mandri Eesti ning Lääne-Eesti kartulipõldudelt 152 isolaati. Ühe tüüpilise haiguslaiguga lehtede (isolaatide) kogumine toimus haiguse erinevates epidemioloogilistes faasides terve kasvuperioodi vältel. Patogeeni populatsioonide fenotüübiliseks iseloomustamiseks viidi isolaadid puhaskultuuri, milledega hiljem teostati katsed, selgitamaks välja paarumistüüpide ning virulentsusfaktorite esinemine. Paarumistüüpide kooseksisteerimine põldudel näitab potentsiaali suguliseks paljunemiseks ning oospooride tekkeks, mis on oluline näitaja populatsioonide iseloomustamiseks. Mandri Eestis jagunes paarumistüüpide suhe peaaegu 1:1, saartel domineeris A1 (70,5%). Saarte omavahelises võrdluses domineeris Saaremaal A2, ning Hiiumaal A1, mistõttu oli Saaremaal A2 paarumitüüpide esinemissagedus sarnane mandri Eestiga. 3 Virulentsusfaktoreid on kokku 11, mis kõik suudavad jagu saada kartuli resistentsusgeenidest (r-geenid), mida on samuti 11. Saarte ja mandri omavahelises võrdluses jäi keskmiseks virulentsusfaktorite arvuks 6,1 (mandril) ja 6,5 (saartel) ning domineerivaks patotüübiks (rassiks) kujunes 1.2.3.4.7.10.11. Leitud rass sarnanes varasemate uuringute käigus, Eestis ning Euroopas, leitud rassidega. Lääne-Eesti saartel levivaid populatsioone tuleks kindlasti edasi uurida kuna ühe aasta tulemused ei iseloomusta saarte populatsioonide tegelikku olukorda.Phytophthora genus includes more than 60 species of important plant pathogens, which Phytophthora infestans is one of the most studied pathogen worldwide. Late blight pathogen, which is a fungus-like microorganism laid the foundation for phytopathology as science, and its development and spread are still being researched. In Europe and also in Estonia spreads pathogen „new“ population which owns two mating types, designated A1 and A2 and is able to reproduce sexually by forming oospores. It also has changed pathogen ecology, epidemiology, virulence, fungicide resistance and resistance to unfavorable weather conditions. Estonian populations of P. infestans have been previosly studied only in mainland. Late blight isolates collecting from Estonian islands started in 2012 to study which populations are spreading there because before this thesis it was unknown. The aim of the research was to investigate whether populations of the Estonian islands is similar or not compared to the continental populations of Estonia. In 2012 a total of 152 isolates from potatofields in Estonian mainland and western islands were collected. Isolate collection was carried out troughout the growing season in various epidemiological stages of the pathogen. For phenotypic characterization of the pathogen populations collected isolates were grown in vitro for conduct experiments to establish the presence of virulence factors and mating type. Mating type coexistence in fields shows potential for sexual reproduction and forming oospores, which are an important indicator for the populations characterization. In Estonian mainland the mating type proportion was almost 1:1, in islands the dominant mating type was A1 (70,5%). When compared islands together it was shown, that mating type A2 dominated in Saaremaa unlike Hiiumaa where the dominant one was A1 mating type. Because of that the Saaremaa A2 mating type proportion was similar to the mainland. 5 There is a 11 known virulence factors that can all overcome 11 potato resistance genes (r-genes). Through the comparison of Estonian islands and mainland the average number of virulence factors were 6.1 (in mainland) and 6.5 (in islands) and the dominant pathotype (race) was 1.2.3.4.7.10.11. Found race was similar to the previous race surveys which were conducted in Estonia and Europe. The populations situation in West-Estonian islands should be definitely investigate further because the one-year results doesn’t characterize pathogen populations in long-term

The potato late blight pathogen Phytophthora infestans: changes in epidemiology and population structure

Kartuli-lehemädanikku põhjustav patogeen Phytophthora infestans on pälvinud palju tähelepanu kartulikasvatajate kui ka fütopatoloogide seas. Niiskuse ja jahedate temperatuuride ( < 20 ˚C ) olemasolul võib patogeen hävitada terve kartuli maapealse ja –aluse osa v.a juured, vähem kui nädalaga. Enam kui pooleteise sajandi jooksul on selle haigustekitaja leviku piiramiseks ja tundmaõppimiseks välja töötatud suurel hulgal fenotüübilisi ja geneetilisi markereid. Viimase kolmekümne aasta jooksul on üritatud tõrjuda patogeeni „uut“ suguliselt levivat populatsiooni, mis on vastupidavam keskkonna- ja ilmastikuoludele ning püsides nakkuslik mitu aastat järjest. Käesoleva töö eesmärgiks oli selgitada muutusi, mis on toimunud patogeeni epidemioloogias ning populatsioonide struktuuris. Millisel määral ja kui palju on pooleteise sajandi jooksul patogeen muutunud. Uurimustöös kasutati vanemaid ja uuemaid võõrkeelseid retsenseeritud teadusartikleid, mille andmeid oleks võimalik omavahel võrrelda ning antud töös kasutada. Antud töös toodi välja millised muutused on toimunud P. infestans patogeeni epidemioloogias ning populatsioonides. Viimase kolmekümne aasta jooksul on need märgatavalt muutunud. „Vana“ populatsioon, mis levis vegetatiivselt on „uue“ populatsiooni poolt välja vahetatud (eelkõige Euroopas). „Uus“ populatsioon levib suguliselt, mille tagajärjel võivad tekkida oospoorid. Sellest tulenevalt lööbib nakkus põldudel varem, patogeeni eosed on elujõulisemad ja vastupidavamad keskkonna- ja ilmastikuoludele suutes nakkuslikud püsida mitu aastat järjest. Euroopas on erinevate teadlaste katsete tulemusena leitud suur populatsioonide genotüübiline mitmekesisus ning kõrge A2 paarumistüüpide esinemissagedus, mis võib viidata sugulisele paljunemisele.Potato pathogen Phytophthora infestans that causes potato late blight, has attracted a lot of attention among the potato growers and phytopathologists. Precence of humidity and cool temperatures (<20 ˚ C) are perfect for the pathogen to destroy a whole potato and ground-share basis excluding the roots, less than a week. More than over a 165 years learning of the pathogen has helped develope a large amount of phenotypic and genetic markers. Over the last thirty years has been tried to control the pathogen "new" sexually spreading population, which is more resistant to environmental and climatic conditions, and the infection persists for several years in a row. Purpose of this study was to identify the changes that have occurred in the epidemiology and population structure of the pathogen. To what extent and how much the pathogen has changed over the 165 years. In this study was used older and newer foreign-language reviewed research articles, and the data was compared with each other in this paper. The aim of this work was to brought out what changes have occurred P. infestans pathogen populations and epidemiology. Over the last thirty years, they have changed significantly. „Old“ population, which spread vegetatively has been replaced by a „new“ population (especially in Europe). The "new" population spreads sexually, which may cause oospores. Becuse of this pathogen infects fields nearly a month earlier, the pathogen spores are viable and resistant to environmental and weather conditions, being able to remain infectious for several years in a row. In Europe has been found a large genotypic diversity in populations, and the high incidence of mating type A2, which may indicate sexual reproduction

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