New insights into genotypic thermodependency of cytoplasmic male sterility for hybrid barley breeding

Abstract

The cytoplasmic male sterility (CMS) system msm1 in barley is known to be thermosensitive, sometimes resulting in spontaneous fertility restoration in the absence of the corresponding restorer gene Rfm1. Here, we investigated genotypic differences concerning temperature sensitivity and the plant developmental stage at which elevated temperature induces spontaneous fertility restoration in three CMS mother lines. While one line stayed completely male sterile, a significantly higher fertility was observed in two lines after treatment from growth stage DC 41 until maturation. Microscopic analysis revealed that sterile anthers contained neither intact pollen, nor remains of aborted pollen grains, whereas pollen was visible in anthers of potentially fertile plants. We conclude that the barley CMS system affects anther and pollen development prior to meiosis. Elevated temperature during heading and flowering can lead to a spontaneous fertility restoration by reactivating pollen growth. Nevertheless, genotypic variation exists enabling the selection for stable CMS mother lines and the development of F1 hybrids with high hybridity. As spontaneous fertility restoration due to environmental effects is difficult to phenotype, further investigations will focus on the development of molecular markers for marker‐assisted selection.

High intraspecific diversity of Restorer‐of‐fertility‐like genes in barley

“…As these hybrids were shown to display several advantages over non‐hybrid varieties, including consistency in the seed yield from year to year by better overcoming severe weather conditions and higher resistance to diseases, the prospective benefits of breeding hybrid varieties in barley based on CMS are promising (Muhleisen et al ., , ,b). However, the application of Rfm1 ‐CMS in hybrid breeding in barley is limited due to its thermosensitivity, as spontaneous fertility restoration in the absence of the Rfm1 gene occurs during periods of higher temperatures around heading and flowering time (Bernhard et al ., ). Therefore, the identification of new sources of CMS and alternative restorer genes, the most likely origin of which will be RFL genes from wild barley relatives, will be crucial for the development of new hybrid varieties.…”

A novel way to identify specific powdery mildew resistance genes in hybrid barley cultivars

“…Heterogeneity of hybrid cultivars (F 1 generation) can be caused by more than two genotypes involved in their formation, for example a male sterile female parent, a fertility restorer male parent and fertile maintainer 6 . Heterogeneity may also result from self-pollination if the cytoplasmic male sterility becomes unstable through environmental factors including temperature 35 . Second, some parental cultivars may consist of more than one line.…”

Temperature related instability of a naturally induced cytoplasmic male sterility in industrial chicory (Cichorium intybus L.)

“…In barley, the msm1 CMS system is thermosensitive. Fertility is restored by high temperatures depending on the genotype (Abdel‐Ghani et al., ; Bernhard et al., ). In Brassica napus , both the stability of the pol and nap CMS system are sensitive to elevated temperatures (Burns et al., ; Fan & Stefansson, ).…”

“…However, temperature is the most important environmental factor causing CMS instability in different crops. In Hordeum vulgare , maternally transmitted CMS from H. spontaneum is no longer active during elevated temperatures during heading and flowering (Abdel‐Ghani, Frey, & Parzies, ; Bernhard, Friedt, Snowdon, & Wittkop, ). A similar thermo‐sensitive system has been described for CMS in wheat with Aegilops kotschyi cytoplasm (Song et al., ).…”