GENETIC DIVERSITY IN APRICOT, PRUNUS-ARMENIACA, AIMED AT IMPROVING RESISTANCE TO PLUM POX VIRUS

Plum Pox Virus, a non-persistent virus transmitted by aphids, causes s erious damage to stone fruits. The apricot tree is very Sensitive and in order to breed apricot cultivars resistant to Plum Pox Virus and es tablish breeding strategies, genetic diversity based on 10 enzymatic s ystems, six of which were polymorphic, has been studied. The plant mat erial studied, 94 accessions, included the most important apricot cult ivars grown in PPV-affected areas. Genetic diversity is high and showe d important differences between the three geographical groups studied (North African, European and North American). The North American group was very diverse and allozymes can be used to identify three subgroup s. Some North American PPV-resistant cultivars were very distant from the rest of the cultivars, mainly due to the presence of rare alleles found in an Asian apricot related species. These results support the h ypothesis that Asian-related species might be the origin of PPV resist ance within the North American cultivars. Three North American cultiva rs have been considered as putative donors of PPV resistance to the Eu ropean cultivars because of their agronomic behaviour; chilling requir ements and distance from European cultivars. However, to increase the genetic variability of the European group and thereby to favour recomb ination, the study of Asian apricot resources is also recommended.