Infraspecific differentiation of garlic (Allium sativum L.) by isozyme and RAPD markers

Abstract

Garlic (Allium sativum L.) is a sterile species of considerable variability with respect to morphological and physiological features. The crop presumably originated in West to Middle Asia from its progenitor A. longicuspis Regel and was transported from there to the Mediterranean and other areas of cultivation. In order to clarify older classification schemes, often based on small or biased collections, we used isozyme and RAPD markers to analyze and structure a collection of 300 accessions, many of which were gathered in Middle Asia close to the assumed center of origin. All of the accessions were first investigated with isozymes, and 48 were selected for a RAPD analysis. The resulting molecular markers were used to construct neighbor-joining dendrograms to group the accessions and to indicate the genetic distances between them. Based on the dendrograms and in conjunction with some morphological features, we propose an infraspecific classification of garlic with four major groups. In agreement with the results of other workers, A. longicuspis lies within the range of the species A. sativum. Numerous forms with varying degrees of domestication are part of our longicuspis group, from which presumably the more derived cultivar groups originated. The origin and spreading of the crop are discussed with respect to the geographical distribution and the genetic distances of the accessions.