GENETIC DIVERSITY AND TAXONOMIC RELATIONSHIPS WITHIN THE GENUS LENS AS REVEALED BY ALLOZYME POLYMORPHISM

A survey of allozyme polymorphism at 11 loci was carried out on 439 ac cessions from the genus Lens. This comprised 153 Lens culinaris subsp. orientalis, 35 L. odemensis, 117 L. ervoides, 32 L. nigricans, 2 of a differentiated cytotype of L. nigricans and 100 landrace accessions o f the cultivated lentil (L. culinaris subsp. culinaris), from 10 diffe rent countries. The aim of the survey was to determine intra-specific genetic diversity and species relationships, based on phylogenetic and phenetic analyses, particularly regarding the position of L. odemensi s and the differentiated cytotype oft. nigricans. Diversity was descri bed by three statistics. The level of diversity in the cultivated taxo n was lower than in any of the wild species according to two of these statistics, the percentage of polymorphic loci and mean number of alle les per locus. For the third measure (Nei's mean genetic diversity) it was only greater than L. ervoides. Genetic diversity statistics of th e wild species indicated differences in the nature of between-populati on genetic diversity within the different taxa. Phylogenetic analysis suggests that L. odemensis and L. ervoides evolved from a common ances tor, and L. culinaris subsp. orientalis subsequently evolved from L. o demensis. Phenetic analysis, however, places L. odemensis closer to L. culinaris subsp, orientalis than to L. ervoides. Nei's mean genetic d istance of L. odemensis from both L. culinaris subsp. culinaris (0.204 ) and L. culinaris subsp. orientalis (0.110) was greater than the dist ance between them (0.062). This evidence is not conclusive in determin ing whether L. odemensis should retain its specific status. Further cr ossability studies should be carried out on a range of genotypes to as sess the potential for gene flow. The evidence presented shows the dif ferentiated cytotype of L. nigricans to be quite distinct from other L . nigricans accessions, both phenetically and phylogenetically. This i ndicates that the differentiated cytotype of L. nigricans may constitu te a new taxon. Discriminant function analysis reveals that isozymes m ay be useful in validating species classification.