Date of Graduation

12-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Plant Science (PhD)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

John R. Clark

Committee Member

Maria Elena Garcia

Second Committee Member

Richard E. Mason

Third Committee Member

Craig S. Rothrock

Fourth Committee Member

Allen L. Szalanski

Keywords

Biological sciences, Fruit crops, Genetics, Plant breeding

Abstract

Quantitative trait loci (QTL) utilizing a pedigree-based analysis (PBA) approach was performed in the peach breeding program for the first time. The pedigree consisted of seven-F1 populations, their parents, ancestors, and cultivars. Flesh firmness and titratable acidity (TA) were examined in 2011, 2012, and 2013. For TA, a consistent and strong QTL was identified on the proximal end of linkage group (LG) 5 of the peach genome. For flesh firmness, two QTLs were located on LG 4. The first QTL was located on the chromosomal region where the slow-melting flesh (SMF) DNA test was identified, and the second QTL was identified in the region of the endopolygalacturonase (endoPG) gene. However, the QTLs on LG 4 were not always consistent. These results indicate that PBA approach for QTL analysis can be applied with success in this mature and ongoing peach breeding program with the aim to find molecular markers associated with relevant quality traits, which is the first step to apply marker-assisted breeding (MAB). Also, DNA tests associated with TA and flesh firmness were analyzed with data taken in 2013 and 2014 on this pedigree and other seedlings, selections, and cultivars to predict acidity levels and flesh texture with the final goal to validate these DNA tests and apply MAB. These tests were able to predict correctly the expected acidity levels and flesh textures of the tested individuals.

Firmness and texture are critical traits in blackberry for breeders, growers, and consumers. Crispy and extremely firm fruits were characterized for two blackberry selections which had been observed to have low color reversion (a postharvest disorder). Firmness of these selections and its seedlings were tested in 2013 and 2014. Results indicated that crispy selections had superior firmness and a higher postharvest storage potential compared to cultivars and other selections in the program. These results are important, because firmness will be increased and color reversion will be reduced by use of this germplasm. This research also contributed to better understanding of the physical aspects of crispy and non-crispy genotypes, providing more information about this aspect of blackberries.

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