Utilization of heterotic patterns within Corn Belt germplasm for adapting, grouping and selecting exotic maize populations

This research was conducted with the objectives of determining: (i) potential use of Reid Yellow Dent-Lancaster Sure Crop heterotic pattern (RYD-LSC H-P) in the incorporation of exotic germplasm into Corn-Belt germplasm, (ii) potential use of RYD-LSC H-P in grouping germplasm which has undefined H-P, and (iii) potential use of progeny derived from exotic x adapted populations based on agronomic and grain quality performance. Adaptation over five years of random mating and mild selection of four adapted x exotic populations (NCMT populations) is described. NCMT populations were formed on basis of genetic background, breadth of genetic base, and RYD-LSC H-P. Populations NCMT1 and NCMT2 were defined respectively as narrow and broad genetic base, while NCMT3 and NCMT4 were defined as LSC and RYD types. Selection of full-sib and S$\sb1$ progeny was based on data obtained during summer of 1990, at Lincoln and Mead, NE. The top 60 lines from each population were crossed to FR36 and FR1075, which represent both sides of the RYD-LSC H-P. During summer of 1991 test-crosses from each population were evaluated at York and Lincoln, NE. S$\sb3$ lines per se were evaluated at Lincoln the same year. Results indicated that H-P involved in the formation of populations NCMT3 and NCMT4 was maintained through five cycles of adaptation. Results also support use of H-P for incorporation of exotic into adapted material. Potential for grouping genotypes with undefined H-P was shown in NCMT1 and NCMT2, where approximately 50% of the lines were grouped on each side of the H-P. Proportion of lines of NCMT3 (LSC) and NCMT4 (RYD) was approximately 70% into the expected heterotic side. Favorable adaptation was observed in all NCMT populations, where some test-crosses outyielded B73 x Mo17 and exhibited similar or superior agronomic characteristics. S$\sb3$ lines from NCMT populations also exhibited competitive grain yield and agronomic characteristics compared to inbreds FR36 and FR1075. Additionally, samples from test-crosses of each population had superior grain quality as compared to B73 x Mo17