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

Abstract

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.

Ergot infection in winter rye hybrids shows differential contribution of male and female genotypes and environment

“…Klotz (2002) already showed that, similar to our results, an introgression of already 25% of the IRAN IX gene reduced ergot severity by 70%. It should be noted, however, that hybrids with a maximum percentage of a non-adapted restorer gene suffer from a significant grain yield reduction in earlier backcross stages (Miedaner et al 2017). The variance components of genotype, inoculum, environment and their interactions were all significant, the environment was the most important factor for all traits.…”

“…While the European restorer sources for the P cytoplasm are only partial restorers and prone to environmental changes and the seed parents, non-adapted, monogenically inherited restorer genes from Iranian primitive rye and Argentinean landraces provide nearly full restoration (Miedaner et al 2005). The latter showed, however, a considerable yield penalty even in higher backcross generations (BC 4 to BC 5 , Miedaner et al 2017). Additionally, the amount of pollen available from hybrid cultivars depends on the ease of restoration and/or physiological resistance mechanisms of the female parent.…”

Genetic mapping of pollen fertility restoration QTLs in rye (Secale cereale L.) with CMS Pampa

“…The marker-assisted selection (MAS) breeding process was streamlined by the development of sequencecharacterized amplified region (SCAR) markers based on RAPD and AFLP markers tightly linked to the critical QTLs (Stracke et al 2003). However, long intervals between the markers flanking the Rfp1 (2.9 cm) and Rfp2 (5.2 cm) QTLs are problematic because the region may encode undesirable genes surrounding the introgressed allele (Frisch and Melchinger, 2000;Miedaner et al 2017). Recent development of accurate conserved ortholog set (COS) markers (TC300731 and TC256739) delimiting Rfp1 within a 0.7 cm interval (Hackauf et al 2012) and an EST-derived CAPS marker, c28385, which co-segregates with Rfp3 (Hackauf et al 2017), was also beneficial.…”

New PCR-specific markers for pollen fertility restoration QRfp-4R in rye (Secale cereale L.) with Pampa sterilizing cytoplasm

“…A high linkage drag of undesirable genes with the 4R QTL was observed in hybrids (Miedaner et al 2000(Miedaner et al , 2017. Two markers, namely Xtc256739 and Xtc300731, flanking the Rfp1 gene at distances of 0.3 cM and 0.4 cM were evaluated (Hackauf et al 2012).…”