Virulence, genetic diversity, and putative geographical origin of sunflower broomrape populations in Morocco

Sunflower broomrape (Orobanche cumana Wallr.) was detected for the first time parasitizing sunflower in Morocco in 2016. Seeds of three broomrape populations from two separate areas of Morocco, Souk Al Arbaa (populations SA1 and SA2) and Meknès (Population MK1) were collected. The populations’ virulence, genetic diversity, and putative area of origin were examined. Race classification using a set of sunflower differential lines showed that MK1 was a race-E population, while SA1 and SA2 were race-G populations. The analysis with 192 SNP markers showed that SA1 and SA2 populations are genetically similar and very distant from the MK1 population. The three populations exhibited low intrapopulation diversity. Comparisons with populations from other areas showed that MK1 was introduced from a race-E population from the Guadalquivir Valley gene pool in Southern Spain, probably before 1988. Populations SA1 and SA2 showed close relationships with a population from Russia, although more exact knowledge of the origin of these populations requires further investigation. Since the SA and MK populations were collected from areas located approx. 100 km apart, the risks of mixing and recombining both gene pools to produce more virulent variants must be considered.