Prediction of Semidwarf Culm‐Length Genotypes in Wheat1

Abstract

Two major independent genes, Sd1 and Sd2, control semidwarf culm length in wheat (Triticum aestivum L.) and singly produce very similar culm‐length phenotypes. Culm‐length genotypes of semidwarf lines have normally been determined by evaluating culm‐length distributions for F2 populations of test crosses to known Sd1 and Sd2 lines. In the present study, test crosses of eight semidwarf lines of unknown genotype were made to Sd1 and Sd2 tester lines to test the premise that the magnitudes of variance for coleoptile length and culm length varied directly with one another in F2 populations. The results verified that variance of coleoptile length closely corresponded with the variance of culm length in all F2 populations. The culm‐length genotypes of the eight semidwarf lines were accurately predicted using the F2 coleoptile‐length variance values. The coleoptile test is particularly valuable because measurements can be obtained in 8 days, and the test requires little space and much less labor than the F2 culm‐length method. Identification of culm‐length genotype is a necessary first step before the association of these specific genes with seedling vigor, winter survival, grain yield, quality criteria, and other important traits can be determined.