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Genotypic and Phenotypic Diversity in Ontario Bean (Phaseolus vulgaris) Breeding Germplasm Derived from Interspecific Crosses with Phaseolus acutifolius

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Title: Genotypic and Phenotypic Diversity in Ontario Bean (Phaseolus vulgaris) Breeding Germplasm Derived from Interspecific Crosses with Phaseolus acutifolius
Author: Turner, Fawn
Department: Department of Plant Agriculture
Program: Plant Agriculture
Advisor: Pauls, K. PeterVan Acker, Rene
Abstract: Common bacterial blight (CBB) reduces the overall yield of Phaseolus vulargis L. (common bean), and most importantly, reduces the marketable yield due to lesions and discolouration of the seed, caused by the bacteria Xanthomonas axonopodis. Genetic resistance to CBB has been identified in Phaseolus acutifolius A. Gray (tepary bean), a member of common bean’s tertiary gene pool. Two sources of genetic resistance from tepary bean (PI 319443 and PI 440795) have been incorporated into germplasm in Ontario. A major locus for CBB resistance, introgressed on chromosome 8, has been used to develop several CBB resistant varieties. Whereas CBB resistance is well studied in this germplasm, little work has been done to characterize agronomic traits at large or other possible effects of P. acutifolius introgression. The objectives of this thesis project were to investigate the genetic and phenotypic diversity within the University of Guelph’s bean breeding program (including population structure and evolutionary relationships with tepary bean), to determine trait correlations (including with CBB resistance), and to identify significant marker-trait associations. Thirteen genotypes from Ontario’s bean breeding program and a population of 212 RILs derived from a three-way cross of AC Compass*//Rexeter/Apex were assessed in the field for 23 agronomic traits, and six additional genotypes were used for structure and diversity assessments. Stem colour at harvest was evaluated for the first time in common bean. Gains in selection were seen for several traits, while others had low phenotypic variation in this population. Nucleotide diversity was determined to be 3.4 x 10^-4 and STRUCTURE analyses identified three primary groupings among this germplasm. Evolutionary relationships with tepary bean and CBB resistance were the primary drivers in this population’s structure and patterns among other traits were not as strong. A genome-wide association study (GWAS) with the 13 Ontario genotypes and 212 AC Compass*//Rexeter/Apex RILs identified 172 significant marker-trait associations. Most notably, QTL for yield were stable on chromosomes 2 and 9, and QTL for lodging and harvestability were stable on chromosome 7. The findings of this study offer many opportunities to improve common bean breeding efforts and understandings.
Date: 2021-08
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