Our objective was to compare the phenotypic variability within S2 x S2 hybrids of maize (Zea maize L.) with hybrids of the same lines advanced to the S8 generation and with various check hybrids. Twenty-two S2 x S2 hybrids and their 22 S8 x S6 derivatives, along with six check hybrids, were grown for one year. Plant-to plant variability within each hybrid for nine traits was calculated on the basis of individual plant measurements of 10 plants per plot in 10 replications. Mean yield of the S2 x S2 hybrids was similar to that of the S8 x S6 hybrids. The S2 x S2 hybrids differed significantly in plant-to-plant variability for plant height, ear moisture percentage, ear weight, kernel-row number, and ear diameter. As a group, the S2 x S2 hybrids were significantly more variable than the S8 x S6 hybrids were significantly more variable than the S8 x S6 hybrids for all traits except car diameter. Compared with the check hybrids, the S2 x S2 hybrids were similar to the double-related-line single cross check. All S2 x S2 hybrids had at least three traits more variable than the pure line, single-cross check. Many of the S2 x S2 hybrids, however, were more uniform than the other check hybrids for plant and ear height. The genotypic heterogeneity within the S2 x S2 hybrids accounted for about 32% of the plant-to-plant variability whe compared with the single-cross check, B73 x Mo17. These data suggest that selection among S2 x S2 hybrids may be possible for acceptable plant-to-plant variability. Such hybrids may be advantageous to seed producers because of the grater vigor of the S2 lines for seed production.

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