Contribution of the Long Arm of Chromosome 10 to the Total Haterosis Observed in Five Maize Hybrids

Knowledge of the contributions of different chromosome segments to the expression of quantitative traits is limited. Information on the relative importance of loci on different chromosome arms could be used to identify blocks of genes that might be useful for improving inbreds and their hybrid progeny. One suggested technique to evaluate the relative importance of different chromosome arms of maize (Zea mays L.) for trait expression has been the use of B-A translocations. The objective of our study was to measure the contributions of the 1OL segments from the inbreds B55, CI187-2, Oh43, M14, and N25 to the total heterotic effect observed in the hybrid of W22 and the respective inbreds. Field studies were conducted that included three strains of W22, their crosses to B55, CI187-2,Oh43, N25, and M14; and their crosses to five W22 lines that carried a substitution from each of the five non-W22 lines for the distal 67% of the long arm of chromosome 10 (1OL). Data were collected for 11 plant and ear traits. Significant differences (P ≤ 5 0.05) were detected among the three strains of W22 and their crosses. The differences, however, did not show a consistent pattern among strains for the 11 traits. Significant midparent heterosis was detected for most traits in the hybrids of the normal and 10L segment lines for grain yield and components of yield. The percentage of midparent heterosis accounted for by the 1OL segment ranged from 9.4 to 20.8% for yield. There were differences among traits for the effects of segment 1OL on trait expression, with the greatest effect for tasselbranch number and the least for kernel weight. These studies suggest that the use of B-A translocations to analyze more chromosome segments may be informative and may make possible the combining of different segments for creating superior lines and hybrids. Joint contribution: USDA-ARS and Journal Paper no. J-12931 of the Iowa Agric. and Home Economics Exp. Stn., Project 2728.