II. Genetic Stocks

Necrosis genes in U. S. varieties of common wheat

K. TSUNEWAKI and Y. NAKAI

Laboratory of Genetics, Kyoto University, Kyoto, Japan

Necrosis, which often occurs in wheat hybrids, is classified into necrosis in a narrow sense and chlorosis. Two complementary genes. Ne₁ on chromosome 5B and Ne₂ On chromosome 2B (XIII), control the former (TSUNEWAKI 1960), and genes Ch₁, Iocation unknown, and Ch₂ on chromosome 3D control the latter (HERMSEN 1966, TSUNEWAKI 1966). We are investigating the distribution of those genes in various geographical populations of common wheat in order to throw a light on its phylogenetic differentiation. In this article, results with the U. S. common wheat will be given.

We obtained 300 U. S. varieties of common wheat (Triticum aestivum) from Dr. J. C. CRADDOCK, World Collection of Small Grains, USDA. Of those 282 varieties were crossed to three testers for necrosis and chlorosis genes and their genotypes were determined. The results are given in Table 1. (Detailed analysis of the results was published in the Canadian Journal of Genetics and Cytology Vol. 9 : 385-393, 1967.) Most variety names were abbreviated according to BRIGGLE and HEYNE (Wheat Newsletter 6 : 17-24, 1959). Growth habit of each variety was also determined, as shown in the table by growing plants in growth chambers, that were operated at 20C with 16hr illumination of 20,000 luxes. Varieties that headed after three months from sowing were determined as spring, those with visible ears inside the leaf sheath as intermediate and those showing no ear formation as winter type. Table 1 : pp.10-18.