Polymorphism in the lengths of restriction fragments of;he whole cpDNA mole
cule was studied in cultivated olive and in oleaster (wild olive) over the
whole Mediterranean Basin. Seventy two olive cultivars, 89 very old trees c
ultivated locally, and 101 oleasters were scored for ten endonucleases. Mor
eover, maternal inheritance of cpDNA in olive was shown by analysing the pr
ogeny of a controlled cross between two parents which differed in their cpD
NA haplotypes. In the whole species, three site- and three length-mutations
were observed, corresponding to five distinct chlorotypes. The same chloro
type (I) was predominant in both oleasters and cultivated olive trees, conf
irming that these are closely related maternally. Three other chlorotypes (
II, III and IV) were observed exclusively in oleaster material and were res
tricted either to isolated forest populations or to a few individuals growi
ng in mixture with olive trees possessing the majority chlorotype. An addit
ional chlorotype (V) was characterised by three mutations located in distin
ct parts the cpDNA molecule but which were never observed to occur separate
ly. This chlorotype, more widely distributed than the other three, in both
cultivated and wild olive, and occurring even in distant populations, was o
bserved exclusively in male-sterile trees showing the same specific pollen
anomaly. However, in the present study, no evidence was provided for a dire
ct relationship between the occurrence of the cpDNA mutations and male ster
ility. It is suggested that the large geographic distribution of chlorotype
V may be related to the high fruit production usually observed on male-ste
rile trees. These may be very attractive for birds which are fond of olive
fruit and spread the stones efficiently. Probably for the same reason, peop
le preserved male-sterile oleasters for long periods and, in several places
, used male-sterile cultivars over large areas.