TEMPERATE MAIZE INBREDS DERIVED FROM TROPICAL GERMPLASM .2. INBRED YIELD TRIALS

Tropical maize (Zea mays L.) is a germplasm resource that may contribu te genes for high yield and disease resistance to temperate breeding p rograms. Yet, this resource has not been utilized extensively, mainly because of the poor agronomic performance and photoperiod sensitivity that often accompany tropical germplasm. The objective of this study w as to determine the agronomic performance of 95 inbred lines derived i n North Carolina from 100% tropical germplasm. Ninety-five lines were derived from seven tropical commercial hybrids and intercrosses among them, using two complete cycles of pedigree selection. Visual selectio n emphasized early flowering, silk-tassel synchrony, low ear placement , standability, prolificacy, and ear quality. The inbreeding coefficie nt of plants within these lines was 0.96 to 0.98. Agronomic performanc e was evaluated in inbred yield trials during 1990 at three locations. Grain yields ranged from 0.68 to 3.76 Mg ha(-1). The highest yielding check inbred, NC252 (an improved B73), yielded 3.65 Mg ha(-1), slight ly less than the best experimental inbred. Mean percent stalk lodging ranged from 0 to 16%, and root lodging was infrequent. Grain moisture at harvest was mostly within the range of the checks. The genetic corr elation between grain yield and number of ears per plant was 0.72, whi le the correlation between grain yield and moisture was not significan t. Several lines possessed excellent combining ability and inbred perf ormance. The best Line, 1497-2, produced testcrosses competitive with the best commercial hybrids and as a Line per se performed as well as the best public inbreds available for North Carolina.