Characterization and practical use of self-compatibility in outcrossing grass species

Abstract

Background Self-incompatibility (SI) systems prevent self-fertilisation in several species of Poaceae, many of which are economically important forage, bioenergy and turf grasses. SI ensures cross-pollination and genetic diversity but restricts the ability to fix useful genetic variation. In most inbred crops, it is possible to develop high performing homozygous parental lines by self-pollination which then enables the creation of F1 hybrid varieties with higher performance, a phenomenon known as heterosis. The inability to fully exploit heterosis in outcrossing grasses is partially responsible for lower levels of improvement in breeding programmes compared to inbred crops. However, SI can be overcome in forage grasses to create self-compatible populations. This is generating interest in understanding the genetical basis of self-compatibility (SC), its significance for reproductive strategies and its exploitation for crop improvement, especially in the context of F1 hybrid breeding. Scope We review the literature on SI and SC in outcrossing grass species. We review the currently available genomic tools and approaches used to discover and characterise novel SC sources. We discuss opportunities barely explored for outcrossing grasses that SC facilitates. Specifically, we discuss strategies for wide SC introgression in the context of the Lolium-Festuca complex and the use of SC to develop immortalised mapping populations for the dissection of a wide range of agronomically important traits. The germplasm available is a valuable practical resource and will aid understanding of the basis of inbreeding depression and hybrid vigour in key temperate forage grass species. Conclusions A better understanding of the genetic control of additional SC loci offers new insight into SI systems, their evolutionary origins and reproductive significance. Heterozygous outcrossing grass species that can be readily selfed facilitate studies of heterosis. Moreover, SC introduction into a range of grass species will enable heterosis to be exploited in innovative ways in genetic improvement programmes.

Observed autogamy in Baobab (Adansonia digitata L.)

“…Although, self-incompatibility ensures cross-pollination and genetic diversity, it makes the xing of useful genes di cult (Cropano et al, 2021). In addition, self-compatible clones will not need pollinators when used to establish plantations (Munoz-Sanz et al, 2020).…”

Fine-Mapping and Comparative Genomic Analysis Reveal the Gene Composition at theSandZSelf-incompatibility Loci in Grasses

“…The absence of a functional gene copy of an SI determinant, disrupting the initial self-recognition process, is not the only source of self-compatibility ( Do Canto et al 2016 ). Similarly, a recombination event between the SI determinants, silencing of the SI determinants, or a mutation interfering with the downstream cascade of SI unlinked to the S - and the Z -locus represent other sources of self-compatibility ( Do Canto et al 2016 ; Cropano et al 2021 ).…”

EPFL peptide signalling ensures robust self‐pollination success under cool temperature stress by aligning the length of the stamen and pistil

“…It is also known that environmental changes sometimes induce temporal pollination‐type conversions (Kalisz & Vogler, 2003; Kalisz et al, 2004). Furthermore, it has been pointed out that converting the pollination type from cross‐pollination to self‐pollination could provide an advantage from an agricultural viewpoint because species that can be maintained and propagated by self‐pollination are easily stored and distributed as seeds (Cropano et al, 2021; Yang & Mackenzie, 2019). In this study, we showed that the reduction in EPFL6 activity causes the failure in self‐pollination at a cool temperature (Figure 1).…”