Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/1997
Publication Date: N/A
Interpretive Summary: The commercial corn industry is based on crosses among pairs of highly uniform lines that show superior hybrid performance. A major study was completed in one of these hybrids in which genetic factors (chromosomal segments) were identified that contributed significantly to the yield of grain. It was suspected that some of these chromosomal segments were comprised of several individual genes. This manuscript reports the results from a later investigation in which one of these segments (a region on the fifth corn chromosome that showed a major effect on grain yield) was studied in more depth. It was found that at least four individual genes were present in the targeted chromosomal segment. Results from this and similar studies should provide plant breeders with information that will allow more efficient breeding strategies for generating high performing corn hybrids.
Technical Abstract: In 1992 a study identifying QTLs in a maize B73 x Mo17 population detected a major effect on yield related traits on chromosome 5. To further investigate this effect, a set of BC2S1 lines were created that contained an introgressed segment of Mo17 in a B73 background. A reciprocal set of lines with a B73 donor segment in a Mo17 background was also created. BC2S1 lines were genotyped using 16 RFLP and 2 isozyme markers that mapped to chromosome 5. Using this method, this one large effect on chromosome 5 has been broken into four smaller QTLs. Two of these effects appear to act in a dominant manner, being present in one testcross but not the other. The third QTL suggests additivity with the Mo17 allele always superior. The last effect near UMC1 does not show any consistent mode of expression and could be spurious. The largest of these factors has been mapped to a 13.4 cm interval near AMP3. If the observed results are true, and other QTLs with large effects showed similar complexity, marker aided breeding of these regions could be difficult. Especially if the marker aided breeding was based on early generation (backcross, F2, or F3) data, where the intricate nature of a region cannot be resolved.