An SSR- and AFLP-based genetic linkage map of tall fescue (Festuca arundinacea Schreb.)

Abstract

Tall fescue (Festuca arundinacea Schreb.) is commonly grown as forage and turf grass in the temperate regions of the world. Here, we report the first genetic map of tall fescue constructed with PCR-based markers. A combination of amplified fragment length polymorphisms (AFLPs) and expressed sequence tag-simple sequence repeats (EST-SSRs) of both tall fescue and those conserved in grass species was used for map construction. Genomic SSRs developed from Festuca x Lolium hybrids were also mapped. Two parental maps were initially constructed using a two-way pseudo-testcross mapping strategy. The female (HD28-56) map included 558 loci placed in 22 linkage groups (LGs) and covered 2,013 cM of the genome. In the male (R43-64) map, 579 loci were grouped in 22 LGs with a total map length of 1,722 cM. The marker density in the two maps varied from 3.61 cM (female parent) to 2.97 (male parent) cM per marker. These differences in map length indicated a reduced level of recombination in the male parent. Markers that revealed polymorphism within both parents and showed 3:1 segregation ratios were used as bridging loci to integrate the two parental maps as a bi-parental consensus. The integrated map covers 1,841 cM on 17 LGs, with an average of 54 loci per LG, and has an average marker density of 2.0 cM per marker. Homoeologous relationships among linkage groups of six of the seven predicted homeologous groups were identified. Three small groups from the HD28-56 map and four from the R43-64 map are yet to be integrated. Homoeologues of four of those groups were detected. Except for a few gaps, markers are well distributed throughout the genome. Clustering of those markers showing significant segregation distortion (23% of total) was observed in four of the LGs of the integrated map.

Inheritance Characteristics of Brown Patch Resistance in Tall Fescue

“…Over half of the markers showed Mendelian segregation ratios, with the majority segregating 1:1. Saha et al (2005) reported similar findings for the markers segregating in their mapping population. Thirty nine percent of the markers showed segregation distortion which is higher than the 23% marker segregation disorder reported by Saha et al (2005) using similar markers for the construction of their genetic linkage map of tall fescue.…”

“…Of these, 43 were polymorphic in parent ATM-21, 72 were polymorphic in parent 110-7, and the remaining 20 were segregating from both parental genotypes. As reported by Saha et al (2005), Mendelian inheritance of 1:1 and 3:1 is expected for the segregating molecular markers because tall fescue is an allohexaploid with disomic inheritance. Sixty-one percent of the markers scored followed normal…”

“…Saha et al (2005) developed the first PCR-based genetic linkage map of tall fescue (2n = 6x = 42) using SSR and amplified fragment length polymorphisms (AFLP) markers. One strategy for utilizing genetic information that is attained from developing these genetic linkage maps is to perform comparative mapping.…”

“…These genome relationships ultimately allow for the cross species transfer of information which can enhance our understanding of the underlying genetic mechanisms controlling traits such as disease resistance. Saha et al (2005) developed the first PCR-based genetic linkage map of tall fescue (2n = 6x = 42) using SSR and amplified fragment length polymorphisms (AFLP)…”

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

“…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.…”