HETEROTIC PATTERNS AMONG OPEN-POLLINATED SWEET CORN CULTIVARS

Heterotic patterns in sweet corn are weakly defined, Most sweet corn i nbreds are descended from three open-pollinated cultivars: 'Golden Ban tam', Stowell's Evergreen', and 'Country Gentleman'. Heterotic and phy logenetic relationships among these three cultivars and others are not clearly known, This investigation was designed to investigate the het erotic patterns among some historically important open-pollinated swee t corn cultivars: 'Country Gentleman', 'Golden Bantam','Lindsey Meyer Blue','Stowell's Evergreen','Howling Mob', and 'Pease Crosby', The 15 possible hybrids from the diallel cross plus the 6 parents were grown in midspring and late summer plantings. Heterosis and combining abilit y effects were estimated for 13 traits, Hybrid x planting date interac tions mere significant for most of the main traits, hence, planting da tes were analyzed separately, Average midparent heterosis for grain yi eld was 29.17% in the first planting date and 57.04% in the second pla nting. Midparent heterosis for yield and plant height were highest for hybrids with 'Country Gentleman' as a parent, 'Stowell's Evergreen' w hen crossed to 'Pease Crosby', 'Lindsey Meyer, and 'Golden Bantam' exh ibited high heterosis, The two late-maturity cultivars 'Country Gentle man' and 'Stowell's Evergreen' had higher general combining ability th an the four early-maturity cultivars for most traits, Specific combini ng ability was seldom significant, Yield of 'Country Gentleman' hybrid s averaged over all crosses and planting dates was the highest, These data indicate a strong heterotic pattern-'Country Gentleman' x 'Pease Crosby', 'Golden Bantam', and 'Lindsey Meyer Blue'-and a weaker one-'S towell's Evergreen' x 'Pease Crosby','Golden Bantam', and 'Lindsey Mey er Blue'.