Plant genetic adaptedness to climatic and edaphic environment

Summary Genetic adaptation implies the shaping of population and species gene pools in response to environmental challenges. The two components of the abiotic land environment are climate and soil, both of which determine much of the evolutionary adaptedness of plants as, besides representing a set of surrounding physical, chemical and sometimes limiting traits, they determine the availability of nutrients and energy, of which they are the immediate source. Ecogeographical distribution of species and ecotypes and different physiological mechanisms and developmental patterns are good evidence of plant adaptedness to soil and climate. However, it is not always easy to determine the underlying genetics of adaptive processes, because 1) environmental factors to which the plants are responding are not always evident and are sometimes too complex, 2) several genes may be involved in the response to a given environmental factor, and 3) the same gene/s may be involved in different adaptive responses. In particular, data on Avena species and temperature as a key environmental factor will be used to illustrate some examples of climatic and edaphic adaptedness. Temperature affects the genetic evolution and geographical distribution of all organisms, and a great deal of evidence indicates that species and populations are genetically adapted to different temperature regimes. Isozymes and other molecular markers have helped in the understanding of the genetic basis of adaptedness. There are many examples of correlation between isozyme and DNA-marker variation and environmental differences. For many population geneticists, isozyme markers are just genetic markers with little or no direct involvement in adaptation. However, metabolic processes are controlled by enzymes, influenced by the environment and used to react in response to it. Evidence that isozymes, and perhaps other molecular polymorphisms, are directly involved in adaptedness will be also presented. Molecular genetic analyses at gene and population levels are opening the ways to a better understanding of plant genetic adaptation.