II. STICKLER. F. C. and PAULI, A. W. 1961. Leaf removal in grain' sorghum. I. Effects of certain defoliation treatments on yield and components of yield. Agron. J. 53:99-102. 12. WHITEHEAD,W. L. 1962. The breeding behavior 9f phe)1otypically diverse grain sorghum varieties in hybrid combinations. Ph.D. Thesis.

gorical and continuous variables. The LM combines the levels of all the categorical variables into one unique mul-When evaluating genetic resources, data on continuous and catetinomial variable, W, with m levels; for example, com-

Five cycles of reciprocal recurrent selection in two synthetic varieties of maize (Zea mays L.) were summarized. Yields of the varietal cross and one parental variety were increased significantly, but the yield of the other variety de, creased slightly. Expected gain in the varietal cross yield, calculated from pooled heritabilities and selection differential, was 7.2% per cycle, but observed gain was only 1.7% per cycle.In the sixth cycle, selection among S1 plants was substituted for selection among S0 plants. Selection within the randomly mated varietal cross was initiated for comparison with selection within the two parental varieties individually. Estimates of genetic variance within the parental populations in the sixth cycle were higher than for the three previous cycles, and genetic variance was higher within the randomly mated varietal cross than within the parental varieties.

A diallel of 45 single‐cross hybrids from 10 inbred lines of maize (Zea mays L.), and a balanced set of 45 doublecross hybrids from the same inbred lines plus 10 commercial hybrids, were grown at 21 locations throughout the U.S. Corn Belt in 1965 and 1966. The purpose was to compare the stability of single‐cross and double‐cross hybrids. Two single crosses, as stable as any of the double crosses, were identified. These two single crosses outyielded the four commercial single crosses by 11%, and the three commercial double crosses by 13%. Although single crosses differed in their ability to respond to more favorable environments, the most important stability parameter appeared to be the deviation mean square. Since all types of gene action appeared to be involved in this stability, potentially useful single crosses must be evaluated over a wide range of environmental conditions to identify stable, high‐yielding single crosses for commercial release

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