Hybrid performance among six-rowed × two-rowed winter barleys (Hordeum vulgare L. and Hordeum distichum L.).

A two-rowed winter barley cultivar, Carstens, was crossed with 22 6-rowed barley cultivars and one 2-rowed cultivar. The parents and hybrids, which were 2-rowed, were grown at two locations in two seasons. An F2 generation of each cross was included in the second season. The hybrids and parents were compared for winter survival, heading date, height, number spike bearing tillers, rachis nodes per spike, 1000-kernel weight, and grain weight. The hybrid significantly exceeded the higher parent in most crosses for height, number rachis nodes per spike, and in every cross for 1000-kernel weight. Significant midparent heterosis was observed in most crosses for winter survival. Heterosis for grain weight was obtained in the 2-rowed × 2-rowed cross. The 2-rowed parents were distinctly less hardy than the 6-rowed parents and expression of characters like number of tillers and grain weight was confounded with winter survival. In hybrids from 6-rowed × 2-rowed crosses the increased number of rachis nodes per spike and heavier kernels contribute to higher grain yields, but these influences are offset by the restricted row number and fewer kernels per spike.