Hybrid Rye and Heterosis

This chapter indicates the worldwide distribution and production of rye, reviews the genetical and methodological basis of hybrid rye breeding and seed production, and demonstrates the progress due to hybrid breeding accomplished in Germany during the last two decades. The amount of heterosis in rye is similar to that in maize and thus several times higher than in self‐fertilizing small grains such as wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and rice (Oryza sativa L.). Highest heterosis is found for grain yield and its components kernels per spike and 1000‐kernel weight, whereas plant density usually shows little or even negative heterosis. Significant hybrid vigour also exists for winter hardiness, plant development, pollen production, straw length, and sprouting resistance. Hybrid breeding and seed production in rye is based on cytoplasmic‐genic male sterility as a hybridizing mechanism.