When plant genetic resources people are tired and emotional, and sometimes when they’re not, talk can turn to landraces. What are they? Can they be identified unequivocally? Can they be associated with a geographical location? Are names anything other than a convenient fiction? Whole chapters, if not entire books, have been written on the subject. ((I should know; I wrote one, five years ago, which I’d link to if it had been published.)) There are definitions aplenty, of course, but that’s not the same as an answer.
Wrapped up in the definitions, and the answers, are notions of genetic variability within the landrace population and an element of selection being needed to maintain the landrace’s properties and maybe guide it in new directions. But that, of course, is crucially affected by the breeding biology of the species concerned. Bluntly, species that are reproduced clonally, like figs, say, or potatoes, are unlikely to have any variability within the landrace while those that are obligate outbreeders, such as maize, are going to be much more variable within the population and likely to change over time too. And then there are inbreeders — beans like Phaseolus vulgaris — in which the landrace is probably a mixture of different genetically pretty uniform types, each of which may well breed true, although the proportions of each may vary from season to season and from place to place.
All of which is a long and roundabout introduction to three recent papers in Theoretical and Applied Genetics that tackle the problem of landrace identity, all of them using molecular markers.
Oat (Avena sativa) is normally self-pollinating, but occasional crossing does occur. So we would not expect much variation within a population. Good thing that, because Hermann Buerstmayr and his colleagues sampled DNA from only three individuals in each of 114 oat varieties gathered from around the world. ((Ref to come DOI 10.1007/s00122-008-0843-y))
