About 9% of the total soybean acreage and about 50% of the total corn acreage in Nebraska was irrigated at least once during the growing season in 1975. The 1975 state averages for irrigated soybeans and irrigated corn were 2220 and 7605 kg/ha respectively. Obviously, this yield differential (in relation to the price and production cost differentials) accounts for the reason most farmers utilize their irrigated acreage for corn rather than soybeans.

F2 linkage results are presented in Table 1 with a= XV, b = Xy, c = xY, and d = xy for the gene pairs listed in the fonn of Xx and Vy. Percentage recombination was obtained as previously (Buzzell, 1974). The fg1 gene appears to be loosely linked with dt1 in Linkage Group 5.

Genetic base of major conmercial soybean cultivars is very narrow. The top 10 most widely grown cultivars in the U.S. have been developed from 17 parent lines (Hartwig, 1973). Recently three soybean Plant Introductions, namely, PI 171.451, PI 227.687 and PI 229.358, have been found to have good leaf-feeding resistance to Mexican bean beetle (Epilachna varivestis Mulsant) (Van Duyn et al., 1972) and corn earworm (Heliothis zea Boddie) (Hatchett et al., 1976; Joshi and Wutoh, 1976).