Correlated effects of exotic pollen‐fertility restorer genes on agronomic and quality traits of hybrid rye

In CMS (cytoplasmic male sterility)‐based hybrid rye (Secale cereale L.) breeding, effective pollen‐fertility restoration is an essential prerequisite for achieving maximum grain yield on the one hand and for minimizing ergot (Claviceps purpurea) infestation on the other. Restorer genes for the CMS‐inducing ‘Pampa’ cytoplasm derived from landraces collected in Iran and Argentina are used by breeders for achieving this goal. Here, restorer genes from four germplasm sources (‘Altevogt 14160’, ‘IRAN III’, ‘Trenelense’ and ‘Pico Gentario’) were analysed by producing three‐way cross hybrids between an elite CMS single cross and pollinators with and without a given restorer gene. Materials were evaluated on large drilled plots for restorer index (RI), grain yield, plant height and other traits in six environments. In experiment 1, a restorer gene from ‘Altevogt 14160’ was used. Seven pairs of marker‐selected carrier and non‐carrier backcross lines served as pollinators. In experiment 2, the pollinators were 17 backcross line pairs from the other three germplasm sources. These lines were grouped as high (RI > 67%) and low restorers (RI < 30%), respectively, using testcrosses with a highly diagnostic CMS tester. Hybrids carrying an exotic restorer gene suffered from a significant grain yield reduction by 4.4% and 9.4% and were 9.3 and 4.8 cm taller in experiments 1 and 2, respectively. Thousand‐kernel weight was reduced, whereas quality traits were only slightly affected. For all traits, significant genetic variance existed among the testcrosses to the presence vs. absence of a given exotic restorer gene. This offers a chance for the breeder to reduce or ultimately overcome the presently observed performance reductions brought about by exotic restorer genes.