Third Phase in the Yield Evaluation of Synthetic Varieties of Maize1

Nine synthetic maize (Zea mays L.) varieties, 36 variety crosses, and four single‐cross hybrids were evaluated for yield at eight Corn Belt locations in six states. This is the third phase of a program for sequentially evaluating the yield potential of synthetic varieties developed as improved sources of breeding material. ‘Iowa Stiff Stalk Synthetic #2’ ✕ ‘Pa. Intermediate Synthetic’ and ‘Iowa Stiff Stalk Synthetic #2’ ✕ Iowa Long Ear Synthetic' were the high‐yielding variety crosses. They approached the yield level for two of the single‐cross hybrid checks. The stability parameters showed the regression coefficients to be sirnilar, and the variety crosses had lower deviation mean squares. ‘Iowa Two‐ear Synthetic’ was the highest‐yielding variety per se, and Iowa Stiff Stalk Synthetic the lowest, which agrees with previous phases of testing. Iowa Synthetic #2 and ‘Tuxlan’ included exotic germplasm and yielded as well per se and in crosses as Iowa Stiff Stalk Synthetic. Midparent heterosis in the third phase was 14%.