Identifying open-pollinated populations of field corn as sources of cold tolerance for improving sweet corn

Sweet corn has poor cold tolerance and adaptation to the European Atlantic coast. Our objectives were to identify sources of favorable alleles for improving cold tolerance of three sweet corn hybrids, to compare sources of cold tolerance and early vigor, and to provide additional information on the relationships among different classes of loci and estimators of favorable alleles for cold tolerance. Each of ten field corn populations was crossed to four sweet corn inbreds. The field by sweet corn hybrids, the populations, the inbreds and the target hybrids were evaluated under cold conditions. Estimates of the mean frequencies of four classes of loci in the populations, and six estimators of favorable alleles (lp(iota)mu', PTC, UBND, NI, PNG(g), and PNG(ceg)) and GCA were computed. The population by inbred crosses were significantly different for emergence proportion and survival. Correlations between lp(iota)mu', UBND, PTC and NI were high for emergence proportion. Most estimates of favorable alleles were significantly different from zero but not among populations. PTC was used to choose the best potential donor populations. The US Corn Belt Dent population AS-3(HT)C3 and the Spanish flint population Oroso were the best potential donors of favorable alleles for emergence proportion and survival under cold conditions, respectively. The ability to germinate and survive under cold conditions may be necessary, but it does not ensure adaptation to cold humid springs.