Phytophtora porri Foister VKLJUČUJE DVE RAZLIČNI GOSTITELJSKO SPECIFIČNI VRSTI

  Willem A. Man in ’t Veld1, Arthur W.A.M. de Cock2, Elena Ilieva3 and C. André Lévesque4

1 Plant Protection Service, Department of Mycology, 6700 HC, Wageningen, Nizozemska
2 Centraalbureau voor Schimmelcultures, 3508 AD Utrecht, Nizozemska
3 Plant Protection Institute, Kostinbrod 2230, Sofia, Bulgaria
4 Eastern Cereal and Oilseed Research Centre, 960 Carlington Avenue, Ottawa, Canada

   

Glivo Phytophthora porri smo izolirali iz obolelih rastlin iz rodu Allium in iz rodu Brassica.. Phytophthora porri, izolirana iz rastlin iz rodu Allium, ne more okužiti rastlin iz rodu Brassica in obratno. Morfološke razlike med izolati iz rastlin iz rodu Allium in iz rastlin iz rodu Brassica so komaj opazne in se prekrivajo. Razlike med posameznimi izolati v njihovi sposobnosti za okužbo pa močno nakazujejo, da P. porri sensu lato najverjetneje vključuje dve različni gostiteljsko specifični vrsti. Da bi preverili, če  Phytophthora porri predstavlja eno samo homogeno vrsto, smo uporabili izoencimske analize in sekvenciranje neprevedljivih sekvenc ribosomske DNA (ITS, sestavljen iz ITS1, 5.8S in ITS2). Pri 16 sevih, izoliranih iz rodu Allium, in desetih sevih, izoliranih iz rodu Brassica, smo analizirali izoencime malat dehidrogenaze (MDH), izocitrat dehidrogenaze (IDH) in laktat dehidrogenaze (LDH), ki skupno zajemajo 4 domnevne lokuse. Pri sevih, izoliranih iz rastlin iz rodu Allium, smo odkrili samo 5 izoencimskih alelov, medtem ko so imeli sevi, izolirani iz rastlin iz rodu Brassica, 6 drugačnih alelov. Očitno reprodukcija med obema populacijama ni mogoča zaradi genskih zaprek, ki onemogočajo prosti pretok genov. Sekvenčna analiza ITS regije je dodatno pokazala izrazite in dosledne razlike med izolati iz rastlin iz rodu Allium in izolati iz rastlin iz rodu Brassica. Podobno je restrikcijska analiza mitohondrijske DNA pokazala dosledne razlike med mitohondrijsko DNA izolatov iz rastlin iz rodu Allium in mitohondrijsko DNA izolatov iz rastlin iz rodu Brassica. Na osnovi rezultatov izoencimskih analiz, sekvenciranja ITS regij in  restrikcijke analize mitohondrijske DNA ter na osnovi  morfologije in patogenosti zaključujemo, da Phytophthora porri Foister ni homogena vrsta, ampak dejansko vključuje dve vrsti in sicer Phytophthora porri sensu stricto in Phytophthora brassicae sp. nov. 

 

 

ABSTRACT

  Phytophthora porri Foister harbours two distinct host specific species

 

Phytophthora porri has been isolated from diseased Allium and Brassica plants. Phytophthora porri isolated from Allium is not capable to infect Brassica plants and vice versa. Morphological differences between isolates obtained from Allium and isolates obtained from Brassica are subtle and show overlap. The differential infection capability, however, strongly suggests that P. porri sensu lato possibly contains two different host specific species. Isozyme analysis and sequence analysis of the internal transcribed spacer regions (ITS, consisting of ITS1, 5.8S and ITS2) of the ribosomal DNA gene repeat were used to examine whether Phytophthora porri represents a single homogeneous species. Sixteen strains isolated from Allium, and ten strains isolated from Brassica, were analyzed with malate dehydrogenase (MDH), isocitrate dehydrogenase (IDH) and lactate dehydrogenase (LDH), comprising altogether four putative loci. Five isozyme alleles were only detected in strains isolated from Allium, whereas in strains obtained from Brassica six other alleles were observed. Apparently the two populations are reproductively isolated from each other by genetic barriers to gene flow. In addition sequence analysis of the ITS regions showed marked and consistent differences between isolates from Allium and isolates from Brassica. Similarly, restriction enzyme analysis of mitochondrial DNA revealed that mtDNA patterns of strains obtained from Allium differed consistently from those isolated from Brassica. Based on isozyme data, ITS sequence analysis, restriction enzyme analysis of mitochondrial DNA, morphology and pathogenicity, it was concluded that Phytophthora porri Foister is not a homogeneous species, but actually contains two species, Phytophthora porri sensu stricto and Phytophthora brassicae sp. nov.