Characterization of malus germplasm and QTL mapping of fruit quality traits

It is important to obtain knowledge of the genetics of Malus in order to efficiently maintain genetic diversity, as well as breed and select future apple cultivars. Germplasm characterization can reveal knowledge of genetic relatedness of accessions and is important towards the goal of increasing this genetic knowledge. This can lead to more efficient germplasm management and efficiency in breeding programs such as appropriate selection of genetically diverse parents and selection of superior genotypes. Furthermore, location of quantitative trait loci (QTL) can lead to the development of markers for marker assisted breeding. By selecting for markers closely linked to significant QTL, early selection can efficiently increase the probability of selecting cultivars that have positive fruit-quality attributes. Genetic diversity and relatedness was studied in a Malus germplasm collection to characterize 174 accessions of various Malus species and cultivars. This collection was genotyped using 17 robust simple sequence repeats (SSR) markers spanning all linkage groups. SSRs are particularly useful markers as they are co-dominant, highly variable, highly reproducible, and require a very small amount of DNA. Multiple alleles were amplified for all SSRs. Phenotypic traits were recorded, including fruit size, fruit weight and fruit shape, and fruit quality characteristics including firmness, total soluble solids, and total titratable acids, were evaluated. Cluster analysis was performed and dendrograms revealing four and five distinct clusters were constructed based on both genotypic and morphological data, respectively. Additionally, QTL were identified for a segregating mapping population of ‘Co-op 17’ x ‘Co-op 16’ cross. Phenotypic data were collected for fruit firmness, shape, weight, total soluble solids, and total titratable acids. A total of 502 SSRs derived from three sources, bacterial artificial chromosome (BAC) end sequencing, expressed sequence tag (EST) sequences, and previously published markers, were used to genotype progeny. Linkage groups were mapped, and despite genotype by environment interactions and sometimes low heritability, 21 QTL were mapped using simple interval mapping. Kruskal-Wallis rank sum test and multiple QTL mapping were performed to validate putative QTL.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2010

Author dc:creator

• Potts, Sarah M.

Contributors dc:contributor

• Korban, Schuyler S.

• apple
• malus
• germplasm
• diversity
• Quantitative trait loci (QTL)

Statement dc:rights

• Copyright 2010 Sarah Marie Potts

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/17042

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/17042