Prospects for applications of genomic tools in registration testing and seed certification of ryegrass varieties

Abstract

The ryegrass (Lolium) species, perennial ryegrass (Lolium perenne L.) and Italian ryegrass (Lolium multiflorum Lam.), are the two most important pasture grass species for global temperate regions and are also useful for amenity purposes. Due to an outbreeding reproductive habit, high levels of genetic heterogeneity are present within cultivated varieties. A continual increase in delivery of new cultivars to the marketplace, along with limited capacity to discriminate on the basis of morphological characteristics in a grow-out test, has caused difficulties for distinctness, uniformity and stability (DUS) testing in the current plant variety protection (PVP) system. A range of genomic tools and resources have been generated for ryegrasses, which provide new opportunities and challenges to the current PVP system. In this review, the currently available genomic tools and resources are described, along with prospects for applications to the PVP system and testing for seed certification and purity accreditation.

Exploitation of data from breeding programs supports rapid implementation of genomic selection for key agronomic traits in perennial ryegrass

“…Phenotypic selection for traits of lower genetic complexity such as heading date and also awning, leaf width and length and growth habit, is currently required to achieve registration of Plant Breeders Rights/Plant Variety Rights, under distinctiveness, uniformity and stability (DUS) standards (Wang et al 2016a, b). However, compared to biomass yield, these traits have minimal (if any) direct impact on agronomic performance and instead limit genetic gain by increasing the length of the breeding cycle (through a requirement for additional evaluation trials) and hindering direct agronomic selection (Wang et al 2016a).…”

“…However, compared to biomass yield, these traits have minimal (if any) direct impact on agronomic performance and instead limit genetic gain by increasing the length of the breeding cycle (through a requirement for additional evaluation trials) and hindering direct agronomic selection (Wang et al 2016a). Until systems are altered to allow registration based on genotypic profile, genomic selection (as demonstrated for heading date) may permit selection for discriminatory characteristics at the same time as more important agronomic traits, without requiring additional lengthy and laborious trials which impose negative impacts on genetic gain.…”

“…Phenotypic selection for traits of lower genetic complexity such as heading date and also awning, leaf width and length and growth habit, is currently required to achieve registration of Plant Breeders Rights/Plant Variety Rights, under distinctiveness, uniformity and stability (DUS) standards (Wang et al 2016a , b ). However, compared to biomass yield, these traits have minimal (if any) direct impact on agronomic performance and instead limit genetic gain by increasing the length of the breeding cycle (through a requirement for additional evaluation trials) and hindering direct agronomic selection (Wang et al 2016a ). Until systems are altered to allow registration based on genotypic profile, genomic selection (as demonstrated for heading date) may permit selection for discriminatory characteristics at the same time as more important agronomic traits, without requiring additional lengthy and laborious trials which impose negative impacts on genetic gain.…”

“…However, such assessment is not appropriate for individual plants that are the target of selection in the early stages of breeding programs, which are typically grown under spaced or semi-spaced conditions in order to identify elite genotypes as parents for synthetic varietal production. Moreover, limited correlation has been observed between biomass yield estimates from spaced plants and corresponding sward-based performance (Wang et al 2016a , b ).…”

Insights into deployment of DNA markers in plant variety protection and registration

“…Arens et al 2010), or traits of a quantitative nature (e.g. the time of flowering) which comprise the majority of descriptors in many outbreeding species, such as ryegrass (Wang et al 2016). The measurement of traits is also time-consuming and requires skill and adequate experience (Reid and Kerr, 2007) and in some cases, special conditions or trial designs are required to conduct the tests (e.g.…”