Genetic diversity in coconut (Cocos nucifera L.) revealed by restriction fragment length polymorphism (RFLP) markers

A study of the genetic diversity in coconut by RFLP analysis was performed in 100 individuals representing 10 Tall and seven Dwarf local populations or 'ecotypes' from various geographical origins. Nine cDNA clones from rice, one mitochondrial DNA clone (CoxI) and one genomic clone (rDNA) from wheat were used as probe for southern hybridization. The distribution of the 40 polymorphic bands revealed by rice cDNA clones was studied using a multivariate analysis and allowed to identify two main genetical groups. The first one includes the ecotypes from the Far East and from the South Pacific, whereas the other one comprises the ecotypes from India, Sri Lanka and Western Africa. The rDNA and the CoxI probes confirm this distinction. The Far East and the Pacific regions which were the most likely center of origin also exhibit the widest polymorphism. The associations between the Panama Tall and the Pacific group and between the West African Tall and the Indian Ocean group reflect their likely origin. The Comoro Tall appears to be intermediate between the two main groups, and could reflect the old migration route between Indonesia and Madagascar. All Dwarf varieties belong to the first group, even those collected in West Africa. Those were probably introduced from Asia and Pacific at the beginning of the century. The cross-pollinating Tall ecotypes were generally more polymorphic than the self pollinating Dwarf ecotypes. The legitimacy of two hybrids between ecotypes was confirmed and maternal inheritance of mitochondrial genome was observed.