Browsing by Subject "Honeycrisp"
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Item Characterizing the host response and genetic control in 'Honeycrisp' to apple scab (Venturia inaequalis)(2014-01) Clark, Matthew DanielTwo novel apple scab resistance loci have been identified in the apple cultivar Honeycrisp, an emerging cultivar in North America that is utilized in apple breeding programs worldwide. Greenhouse inoculation experiments with the apple scab fungal pathogen, Venturia inaequalis, identified a resistance defense response in `Honeycrisp' and its ancestors `Keepsake', `Frostbite', and `Northern Spy' seven days after inoculation. The defense response ranged from necrotic and chlorotic lesions to stellate necrosis and class 3b lesions (with sporulation). A hallmark of the resistance defense response is autofluorescence at the infection site in cleared leaf tissue. Several `Honeycrisp' progeny populations were screened with monoconidial isolates of V. inaequalis and segregated 3:1 for resistance, suggesting two resistance genes inherited from `Honeycrisp'. A consensus `Honeycrisp' linkage map with 1091 SNP markers was constructed for use in mapping. Two resistance loci were mapped using linkage mapping and quantitative trait loci mapping approaches. Marker haplotypes were constructed to trace the inheritance of resistance loci. Rvi19 mapped on linkage group 1 at ~50 cM. In the Rvi19 haplotype, the 138 bp allele for the Ch-Vf1 marker cosegregates with resistance, and is identical by state (IBS) with the Rvi17 resistance in `Antonovka'. Rvi19 is transmitted from `Frostbite' to `Keepsake' to `Honeycrisp', and into the resistant progeny of `Honeycrisp'. The other locus, Rvi20, mapped onto linkage group 15, and is IBS with a marker haplotype found in the susceptible cultivar Golden Delicious. Rvi20 is transmitted to `Honeycrisp' from an unknown parent. Molecular marker haplotypes were used to identify advanced selections in the University of Minnesota breeding program with pyramided scab resistance. Candidate genes were identified at each haplotype that can serve as starting points for identifying the functional genes conferring resistance. A collection of V. inaequalis isolates was assembled and curated from six locations in Minnesota for screening scab resistance. These 80+ isolates were examined for genetic diversity and population structure and provide a snapshot of the diversity of the pathogen present at this time.Item Elucidation of the extended pedigree of ‘Honeycrisp’ apple and genetic architecture of its susceptibility to soft scald and soggy breakdown postharvest fruit disorders and zonal leaf chlorosis disorder(2017-06) Howard, NicholasThe apple (Malus × domestica) cultivar Honeycrisp has become important economically and as a breeding parent due to its ultra-crisp fruit texture, its ability to retain this high level of fruit crispness in storage, and its resistance to apple scab. However, ‘Honeycrisp’ has several detrimental traits that have not been satisfactorily evaluated genetically. Additionally, the original pedigree records for ‘Honeycrisp’ were previously determined as incorrect and this lack of pedigree information has impeded thorough genetic analyses in studies involving ‘Honeycrisp’. The objectives of the research in my dissertation were to identify and genetically describe the parents and grandparents of ‘Honeycrisp’ and to use this new pedigree information in pedigree-based analyses to examine the genetic architecture of its susceptibility to fruit soft scald and soggy breakdown postharvest fruit disorders and zonal leaf chlorosis disorder. Towards these objectives, a high quality genetic map was created using single nucleotide polymorphism data from the apple 8K Illumina Infinium® SNP array and five large families with ‘Honeycrisp’ as a common parent. ‘Keepsake’ was verified as one parent of ‘Honeycrisp’ and ‘Duchess of Oldenburg’ and ‘Golden Delicious’ were identified as grandparents through a previously unknown parent that was identified to be the University of Minnesota selection MN1627. Two quantitative trait loci (QTL) were consistently identified on linkage groups (LGs) 2 and 16 for both soft scald and soggy breakdown. ‘Honeycrisp’ is homozygous for an identical by state haplotype identified at the LG2 QTL that was consistently associated with increased incidences of soft scald and soggy breakdown. ‘Honeycrisp’ inherited the deleterious haplotypes at the LG2 QTL from grandparent ‘Keepsake’ and great-grandparent ‘Grimes Golden’. A large effect QTL for zonal leaf chlorosis was identified on LG9 and a recombinant haplotype that ‘Honeycrisp’ inherited from ‘Duchess of Oldenburg’ at this QTL was associated with increased ZLC in offspring of ‘Honeycrisp’. The LG9 QTL was located approximately between 5 and 10 cM away from a major QTL for skin over color. ‘Honeycrisp’ is heterozygous for skin over color at this location. In ‘Honeycrisp’, the haplotype associated with increased zonal leaf chlorosis at the LG9 QTL is in coupling phase with the haplotype associated with red color at the LG9 skin over color QTL. All of these major QTL were consistently identified across all years of analysis. These new discoveries will be useful in apple breeding efforts involving ‘Honeycrisp’, its ancestors, and its progeny.