Cytoplasmic Male Sterility (CMS) — Rye

In winter rye breeding, the primary CMS systems are the P-type (Pampa) and G-type (Gülzower). The P-type is characterized by the difficulty in selecting restorers due to the low frequency of corresponding genes in natural populations. The application of these systems eliminates the need for manual emasculation when producing hybrid seeds, ensuring the development of heterotic forms with yields 10–12% higher than those of population varieties.

To evaluate these systems, the fertility restoration index (RI) is used, determined in testcrosses as a percentage. RI values below 1–2% are characteristic of maintainer lines, whereas full grain set in commercial hybrids requires RI values ranging from 67% to 90%. The stability of sterility expression in the female line and the efficiency of fertility restoration in the male parent are critical factors in preventing floret sterility.