Creation of a framework genetic linkage map of colonial bentgrass and the identification of genomic regions associated with dollar spot resistance

Abstract

Creeping bentgrass (Agrostis stolonifera L. 2n=4x=28, A2A2A3A3) is a cool season turfgrass known for its lateral growth habit, fine texture and ability to tolerate low mowing heights. One of the biggest maintenance problems for creeping bentgrass is the fungal disease dollar spot caused by Sclerotinia homoeocarpa. Currently the disease is controlled through heavy fungicide use but a more practical long term approach lies through the development of resistant cultivars. Colonial bentgrass (A. capillaris L. 2n=4x=28, A1A1A2A2) is a species related to creeping bentgrass which is resistant to dollar spot. We have generated fertile creeping x colonial bentgrass interspecific hybrids. One plant, designated TH15, was backcrossed with a different creeping plant to generate a mapping population which segregated for dollar spot resistance. The objective of this thesis was to determine which areas of the colonial bentgrass genome are associated with dollar spot resistance. To do this we used the hybrid backcross population to generate a framework genetic linkage map of colonial bentgrass. We created and annotated EST libraries for both creeping and colonial bentgrass and used these libraries as a resource for mapping genes. A new approach to marker development, termed dideoxy polymorphism scanning, was developed to efficiently map genes on the colonial bentgrass map. The colonial bentgrass linkage map contains 212 AFLPs and 110 gene based markers and totals 1157 cM. By comparing phenotypic data obtained from field trails we identified regions potentially associated with dollar spot resistance in colonial bentgrass. The segregation of resistance in the backcross population suggests a three gene recessive epistasis model for dollar spot resistance in colonial bentgrass. By comparing genotypes we identified colonial bentgrass loci on groups 2A1 and 3A1 that are common in all resistant individuals. We hypothesize that genes related to dollar spot resistance may lie on these groups. Other resistant backcross individuals not included in the mapping population also shared these loci proportions significantly higher then expected by random chance (p < 0.05). This lends additional support to our model of dollar spot resistance in colonial bentgrass.%%%%