About 600 cultivars or strains of wheat, collected from Mediterranean countries, including the USSR, and classified as
Triticum aestivum, T. compactum, T. spelta, or
T. macha of common wheat, were studied for necrosis and chlorosis genotypes by crossing them to three testers of known genotypes. On the basis of the results, the geographical distributions of
Ne1 and
Ne2 genes for necrosis and
Ch1 and
Ch2 genes for chlorosis were clarified.
For necrosis genes, the western border of the Asian type population, in which
Ne1-carriers predominate over
Ne2-carriers, extended from Egypt to the Caucasus through Turkey. Between two areas occupied by the Asian type population and the Western type population, in which
Ne2-carrier are dominant over
Ne1-carriers, transitional type populations containing both
Ne1- and
Ne2-carriers at moderate frequencies were found. This transitional zone covers Portugal, Spain, Italy and the USSR (excluding the Caucasus). Two non-carriers regions, where frequencies of both
Ne1 and
Ne2-carriers were very low, were found in this area. These are the Balkan Peninsula (Yugoslavia, Rumania, Bulgaria, Greece and Western Turkey) and the Near East (South Turkey, Syria, Lebanon and Jordan). The latter is, however, not definitive, because of the small number of materials examined. An
Ne1-carrier region, where the frequency of
Ne1 gene is extremely high (60-99%), was found in the North Iran-Armenia-Central Turkey region.
For chlorosis genes, the common wheat populations of all countries investigated showed extremely high frequencies of
Ch2-carriers (88-100%). No
Ch1-carrier was found, except two collections of
T. macha from the Caucasus. Thus, the Mediterranean population of common wheat is the same as those in other parts of the world.
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