Genetic linkage mapping of an annual × perennial ryegrass population

Abstract

Annual (Lolium multiflorum Lam.) and perennial ( L. perenne L.) ryegrass are two common forage and turfgrass species grown throughout the world. Perennial ryegrass is most commonly used for turfgrass purposes, and contamination by annual ryegrass, through physical seed mixing or gene flow, can result in a significant reduction in turfgrass quality. Seed certifying agencies in the United States currently use a test called seedling root fluorescence (SRF) to detect contamination between these species. The SRF test, however, can be inaccurate and therefore, the development of additional markers for species separation is needed. Male and female molecular-marker linkage maps of an interspecific annual x perennial ryegrass mapping population were developed to determine the map location of the SRF character and to identify additional genomic regions useful for species separation. A total of 235 AFLP markers, 81 RAPD markers, 16 comparative grass RFLPs, 106 SSR markers, 2 isozyme loci and 2 morphological characteristics, 8-h flowering, and SRF were used to construct the maps. RFLP markers from oat and barley and SSR markers from tall fescue and other grasses allowed the linkage groups to be numbered, relative to the Triticeae and the International Lolium Genome Initative reference population P150/112. The three-generation population structure allowed both male and female maps to be constructed. The male and female maps each have seven linkage groups, but differ in map length with the male map being 537 cm long and the female map 712 cm long. Regions of skewed segregation were identified in both maps with linkage groups 1, 3, and 6 of the male map showing the highest percentage of skewed markers. The (SRF) character mapped to linkage group 1 in both the male and female maps, and the 8-h flowering character was also localized to this linkage group on the female map. In addition, the Sod-1 isozyme marker, which can separate annual and perennial ryegrasses, mapped to linkage group 7. These results indicate that Lolium linkage groups 1 and 7 may provide additional markers and candidate genes for use in ryegrass species separation.

Four QTLs determine crown rust (Puccinia coronata f. sp. lolii) resistance in a perennial ryegrass (Lolium perenne) population

“…This figure is in the same order of magnitude as that previously reported in other Lolium studies Jones et al, 2002a, b;Thorogood et al, 2002;Faville et al, 2004;Inoue et al, 2004;Warnke et al, 2004). Apparent segregation distortion can be due to statistical error, genotyping and scoring errors or can be a real biological phenomenon.…”

“…In this procedure, the mapping family consists of an F 1 progeny derived from a pair-cross between two unrelated, highly heterozygous individuals. This mapping approach has been applied with success in several species (apple, Maliepaard et al, 1998;poplar, Wu et al, 2000), and also in Lolium (Faville et al, 2004;Warnke et al, 2004).…”

Orchardgrass (Dactylis glomerata L.) EST and SSR marker development, annotation, and transferability

“…To test the primers within Lolium, two plants that are parents to an interspecific L. perenne (L.) 9 L. multiflorum (Lam. ), MFA 9 MFB, ryegrass mapping population were used (Warnke et al 2004). For all samples, DNA was extracted using the QIAGEN 96-well extraction kit and following the manufacturer's recommendations.…”

“…The remainder of SSR primers showed amplification products larger than the 500 bp capillary gel resolution parameters used, weak amplification, no amplification. When comparing transferability of SSR primer amplification to three related forage grass species, tall fescue (F. arundinaceum), perennial ryegrass (L. perenne), and annual ryegrass (L. multiflorum), 43% (506) of orchardgrass primers amplified strong products among four tall fescue bulk samples, and 39% (457) among the two ryegrass parents of the MFA 9 MFB interspecific mapping population (Warnke et al 2004). …”

“…As EST-SSRs markers are derived from transcribed regions, they are likely to have a high success of amplification and associated gene annotations (Varshney et al 2005), and are useful for in silico comparisons to the homologous sequences in other species (Bushman et al 2008). EST-SSR markers have been used in genetic and comparative mapping in a number of forage grass species (e.g., Jones et al 2002b;Warnke et al 2004;Saha et al 2005;Alm et al 2003;Studer et al 2008). Additionally, EST libraries with long sequence reads constitute crucial reference sequences for further sequencing and functional genomics studies using ''Next-Generation'' methods.…”