Figure 24.  As corn breeders began to develop inbreds and double-cross hybrids in the first half of the 20th century, smut resistance was improved substantially simply by selecting against smut susceptibility in breeding populations and among inbred lines. The improvement of the first group of double-cross hybrids compared to the previously grown open-pollinated cultivars is evident from the distributions of relative smut incidence for 1,052 double-cross hybrids and 340 open-pollinated cultivars evaluated in 48 experiments throughout Ohio from 1933 to 1938. (Data from: Stringfield, G. H., and D. H. Bowman, 1942. J. Am. Soc. Agron. 34:486-494.) BACK