Genetic Diversity And Association Mapping Of Forage Quality In Bermudagrass

Bermudagrass is a warm season grass used for the production of forage and turf.The grass thrives in the tropical and subtropical regions.Due to the recent global warming phenomenon,expansion of the tropical belt has occurred increasing the demand for bermudagrass cultivars suitable for forage production.Unfortunately,being a warm season grass,bermudagrass has poor forage quality.Thus,a need to improve the forage quality of bermudagrass exists.Genetic diversity analysis and association mapping of forage quality followed by the selective choice of bermudagrass accessions meant for forage production is a feasible means of addressing this issue.This thesis presents research work involving wild Chinese,African and commercial bermudagrass accessions to facilitate forage quality association with allele markers and screening for cultivars suitable for establishment of a forage bermudagrass germplasm.Firstly,it reports about genetic diversity analysis and association mapping of forage quality in 60 bermudagrass accessions collected from five geographical regions in China.We analyzed and associated 8 phenotypic traits observed in the wild accession with 1474 allele markers.We therefore phenotyped,genotyped,analyzed population structure,kinship,genetic diversity,and performed marker-trait association.Significant variations in 8 phenotypic and physiological traits were observed among the 60 accessions.A total of 1474 alleles were amplified by 104 SSR primers.The average gene diversity and polymorphic information content(PIC)for the study sample were 0.2097 and 0.1748 respectively.The clustering analysis suggested that geographic origin influenced genetic distances between accessions.A total of 76 markers significantly associated with the traits,each at P<0.01.Remarkably,three of them associated with two traits each at P<0.01.Nevertheless,only 41 significant marker-trait associations(MTAs)were observed after Bonferroni test was separately conducted for each trait.Forty-one microsatellites had significant associations with 8 forage-quality-related traits.Secondly,it gives an account of variation in phenotypic and physiological traits of 264 samples of native bermudagrass from China and Africa as well as commercial cultivars associated with feed value.We analysed the data for 5 traits(Biomass,Crude ash,Crude Protein,Moisture content and Height)using SAS studio university edition.Afterwards,we conducted membership function method of fuzzy mathematics to determine which accessions would be suitable candidates for the establishment of a forage germplasm.We identified six accessions(WBD 117,WBD 82,WBD 18,WBD 28,WBD 125 and HLX-WBD-3)as possible candidates for use in forage production breeding programs because they ranked high in the list of membership function values calculated using five traits as indicators of forage quality.Therefore,the identified marker-trait associations provide a feasible means of genetically improving forage quality in bermudagrass after further authentication.Our study also adds knowledge of bermudagrass wild accessions suitable for use in forage production and improvement of feed value of bermudagrass.