The objective was to study the effects of different plant stand densities on the relationships of important plant and ear characters to grain yield for testcrosses of maize (Zea mays L.) inbred lines. The inbred lines, in the F5 generation and originating from M14xC103, were evaluated in two groups, based on high and low hybrid performance in an earlier study. Our study was done in six environments with low, intermediate, and high stand densities in each environment. At the low density only plant and ear heights were correlated significantly with yield; at the intermediate density ear diameter and shelling percentage, in addition to plant and ear heights, were correlated significantly with yield; at the high density all characters except 300‐kernel weights and dates of pollen shed and silk emergence were correlated significantly with yield.

The F1, F2, F3, and F4 generations of 20 selected maize (Zea mays L.) inbred families were evaluated by testcross performance to determine the efficacy of selection in three successive segregating generations to improve combining ability for yield. Ten lines had high yield performance and 10 lines had low yield performance as determined by testcrosses of the F5 or F6 generation. The high‐performance families had F2's equal to, or better than, their F1 source, and nine families were improved by selection in the F3 or F4, or both. Five low‐performance families had F2 yields below those of the F1 source, and not enough gain by selection was realized to have the F4 at the yield level of the F1. The other five low‐performance families had F2 yields at least equal to their F1 source, but no further gains in yield were obtained by selection.

Signature was redacted for privacy. Signature was redacted for privacy. Signature was redacted for privacy.

No abstract