Genetic diversity in wild cereals: Regional and local studies and their bearing on conservation ex situ and in situ

The current alarming global crisis and extinction of biodiversity affect negatively the planet's biosphere. Conservation of biodiversity is one attempt to alleviate the pending extinction of the biosphere by humans. Genetic diversity, the basis of evolution by natural selection, is gravely threatened in the progenitors of cultivated plants and its exploration, evaluation, conservation in situ and ex situ is imperative to guarantee sustainable development. This is illustrated by the population genetics and ecology of two important progenitors of cereals, wild wheat and barley. The wild cereals are rich in adaptive genetic diversity in the Fertile Crescent, primarily in Israel, which is their center of origin and diversity. The 40-55% intrapopulation diversity level in the wild cereals contrasts sharply with the average of 80% in outbreeders. Genetic diversity in wild wheat and barley is structured, particularly in wild emmer wheat, as an 'archipelago' ecological and genetic structure. These include central, semi-isolated and ecologically peripheral and marginal isolated populations, where specific alleles and allele combinations predominate as coadapted blocks of genes, adaptive to diverse ecological stresses. These involve both physical (climatic and edaphic) and biotic (pathogens and parasites) stresses at macro- and microgeographical scales. Complementary in situ and ex situ conservation is imperative across the geographic range of these species, to safeguard their immensely important genetic resources for crop improvement.