Linkage map construction in allotetraploid creeping bentgrass (Agrostis stolonifera L.)

Abstract

Creeping bentgrass (Agrostis stolonifera L.) is one of the most adapted bentgrass species for use on golf course fairways and putting greens because of its high tolerance to low mowing height. It is a highly outcrossing allotetraploid species (2n=4x=28, A(2) and A(3) subgenomes). The first linkage map in this species is reported herein, and it was constructed based on a population derived from a cross between two heterozygous clones using 169 RAPD, 180 AFLP, and 39 heterologous cereal and 36 homologous bentgrass cDNA RFLP markers. The linkage map consists of 424 mapped loci covering 1,110 cM in 14 linkage groups, of which seven pairs of homoeologous chromosomes were identified based on duplicated loci. The numbering of all seven linkage groups in the bentgrass map was assigned according to common markers mapped on syntenous chromosomes of ryegrass and wheat. The number of markers linked in coupling and repulsion phase was in a 1:1 ratio, indicating disomic inheritance. This supports a strict allotetraploid inheritance in creeping bentgrass, as suggested by previous work based on chromosomal pairing and isozymes. This linkage map will assist in the tagging and eventually in marker-assisted breeding of economically important quantitative traits like disease resistance to dollar spot (Sclerotinia homoeocarpa F.T. Bennett) and brown patch (Rhizoctonia solani Kuhn).

Mapping QTL for dollar spot resistance in creeping bentgrass (Agrostis stolonifera L.)

“…For QTL analysis, linkage maps were constructed separately for each parent '372' and '549' using the double haploid (DH) population type option available in JoinMap (Van Ooijen and Voorips 2001). The marker data set consisted of all the markers (169 RAPD, 180 AFLP, 18 CDO, 3 BCD, 3 RZ and 36 'Ast' creeping bentgrass EST-RFLP markers) that were used to construct our Wrst map (Chakraborty et al 2005), and an additional 98 heterologous (64 CDO, 33 BCD and 4 RZ) and 76 homologous (Ast) EST-RFLP markers. Analysis of QTL for dollar spot resistance was performed using the two parental maps and the marker data sets separately, again using the DH population type option available in MapQTL software (Van Ooijen et al 2002).…”

“…Detailed descriptions of the origin of the parents, selection criteria and development of the population are available in a previous publication (Chakraborty et al 2005). The 697 progeny individuals have been vegetatively propagated in the greenhouse and only 106 progeny from this population were used to generate the Wrst linkage map in creeping bentgrass (Chakraborty et al 2005).…”

“…Enhanced linkage map of the creeping bentgrass population '549 £ 372' An additional 98 heterologous (64 CDO, 33 BCD and 4 RZ) and 76 homologous (Ast) EST-RFLP markers were mapped onto the existing creeping bentgrass linkage map (Chakraborty et al 2005) (Fig. 1).…”

“…As a Wrst step to detect QTL for dollar spot resistance, we have constructed the Wrst linkage map in creeping bentgrass using 169 RAPD, 180 AFLP and 75 RFLP markers (Chakraborty et al 2005). Analysis of QTL requires a linkage map with densely and uniformly distributed markers.…”

“…Analysis of QTL requires a linkage map with densely and uniformly distributed markers. Therefore, we mapped an additional 174 RFLP markers onto the existing map (Chakraborty et al 2005) and then two separate linkage maps were constructed for parents '372' and '549'. These two separate maps were used to accomplish our main objective, which was to detect the number, location and eVect of QTL for dollar spot resistance based on Weld inoculations over multiple years and locations.…”