Pathogenic and molecular diversity in highly virulent populations of the parasitic weed O robanche cumana(sunflower broomrape) from E urope

Summary The parasitic weedOrobanche cumana(sunflower broomrape) constrains sunflower production in eastern and southernEurope and in theMiddleEast. Although genetic resistance is the most effective control method, new parasite races evolve overcoming sunflower resistance. In this work, highly virulent populations ofO. cumanawere analysed for pathogenicity and genetic diversity. The virulence of 11 populations fromHungary,Romania,Spain andTurkey was assessed and compared after infection of sunflower inbred lines to differentiate races of the parasite under glasshouse conditions. Molecular diversity among and within 27 parasite populations was studied byRAPD‐PCR,UPGMAandamovaanalyses. Highly virulent raceFwas identified inHungary,Spain andTurkey. The most virulent race (G) was also found inTurkey. The molecular analysis among highly virulent populations ofO. cumana identified four molecular clusters, respectively, grouping populations fromCentralSpain,Hungary,SouthSpain andTurkey. The genetic homogeneity within parasite populations was confirmed, since no molecular divergences were found within them. This work constitutes the first geographical study ofO. cumanatogether with pathogenicity and molecular traits inherent to each geographical group, and provides useful information for possible phylogenetic analyses ofO. cumana. In addition, molecular markers associated with geographical origin could be developed and used as diagnostic tools to track new broomrape introductions into areas free of virulent races where they might represent a threat to sunflower production.