Eräiden ristisiittoisten viljelykasvien jalostuksesta Yhdysvalloissa

Authors

• Juhani Paatela Maatalouskoelaitos, kasvinviljelysosaslo, Tikkurila

DOI: https://doi.org/10.23986/afsci.71266

Abstract

During the last growth season 1949 the author has had an opportunity to acquaint himself e.g. with the plant breeding work in the United States, especially in Minnesota, Colorado, Utah, New Mexico, and in Beltsville Maryland. In this paper a short survey of the inbreeding, heterosis, and the combining ability has been given. Also the most common methods used in the breeding of corn, sugar beet, and forage crops have been described. As to the corn breeding work the top cross nursery, methods of production of single-cross and double-cross seed, and of maintaining inbred lines for seed production of hybrid corn, predicting the yield of double crosses by means of the yields of single crosses, as well as the three-way cross, and convergent crossing methods, and the production of synthetic variety have been described. The history concerning the breeding of sugar beet in U.S.A. has been shortly reported, including e.g. the methods used in breeding for disease resistance (leaf spot and curly top), selfing and production of hybrids, the means of polyploidy (tetraploids and triploids) as well as male sterility, the breeding for single and double germ seeds in relation to the mechanization of the field operations, and changing the shape of sugar beet from peg-top in shape to globe shape beets in order to get an easy-lifting beet and thus reduce the breakage of roots and costs in harvesting them mechanically. In describing the breeding methods of forage crops the polycross method and its use for producing hybrid seed has been reported in the main points. Comparisons with the open pollinated, polycross progenies and selfed progenies of alfalfa have given equally good results as to the combining ability (57). It therefore seems to be of paramount importance to find as self sterile and as good combining open pollinated lines as possible in order to get the greatest hybrid vigor in double cross hybrids or in synthetic varieties.