NUMERICAL MORPHOLOGICAL ANALYSIS OF LETTUCE CULTIVARS AND SPECIES (LACTUCA SECT LACTUCA, ASTERACEAE)

L. sativa L. cultivars were compared morphologically with accessions of L. saligna L., L. serriola L., and L. virosa L. in order to define the infra- and interspecific variation. Multivariate analysis (principal component analysis) distinguished four groups corresponding with the four species. Infraspecific variation (e.g., colour, leaf shape) within L. sativa is the largest, because breeding has caused a large variation in vegetative features; infraspecific variation within L. serriola is also large. Three plants of one accession were placed between L. sativa and L. serriola because they showed morphological characteristics of both species. They are still classified as L. sativa. The morphological differences between L. sativa and L. serriola are too large to consider these two as one species. The descent of the cultivar groups and the four species is described.