Date of Graduation

12-2011

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor

John R. Clark

Committee Member

Elena Garcia

Second Committee Member

Jon T. Lindstrom

Third Committee Member

Cameron P. Peace

Keywords

Biological sciences; Endopolygalacturonase; Fruit breeding; Fruit flesh; Post-harvest storage

Abstract

This study determined the effect of pre-cold storage treatment on P. persica genotypes, developed a protocol for the evaluation of breeding selection and cultivar storage performance, and provided information on post-harvest performance of these individuals. Additionally, characterization of the peach and nectarine flesh types, validation of endopolygalacturonase (endoPG) DNA markers, and investigation of endoPG marker allele combinations associated with the slow-melting-flesh (SMF) trait were done.

Fruit from 30 individuals were harvested at minimum- and well-mature states. After conditioning for 24 h at 20 ◦C, all 2010 fruit were exposed to 2 min of 1 ◦C 100 ppm chlorinated hydro-cooling, a 2 min 50 ◦C hot water dip, or rinsed with ~2 ◦C water. Fruit in 2011 were not treated due the lack of significant differences among treatments in 2010. All fruit were stored at 1 ◦C for 4 weeks, with samples removed weekly. Changes in soluble solid content (SSC), pH, TA, skin and flesh characteristics, flavor, firmness, mealiness, juiciness, and browning were evaluated. Differences were found between the non-melting, slow-melting, and melting-flesh types and storage length for skin variables, firmness, and juiciness. Interactions among genotypes, maturities, storage lengths, textures, and fruit types were found. To characterize flesh types, validate endoPG DNA markers, and establish allelic associations with SMF, the softening trends of five cultivars, 16 selections, and 142 seedlings were evaluated at the well-mature state and changes in firmness were measured. Leaf samples were collected for DNA extraction and endoPG-6, endoPG-1-SSR, and SNP genotyping. All genotyping was conducted by a collaborating lab with the assistance of the RosBREED project. All results were compared to assess the accuracy of analysis, determine genotype flesh types, and find associations between allelic combinations and the SMF trait. The endoPG-6 marker matched genotypes to melting (MF) and non-melting flesh (NMF) type classifications based on firmness trends in 89% of the genotypes. No specific endoPG-1-SSR or SNP allele combinations were found to be associated with the SMF trait.

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