Date of Graduation

7-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Plant Science (PhD)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

Shi, Ainong

Committee Member

Korth, Kenneth L.

Second Committee Member

Szalanski, Allen L.

Third Committee Member

Kral, Timothy A.

Fourth Committee Member

Srivastava, Vibha

Keywords

Colorimetry; Cultivar development; GWAS; Muscadine; Peach; QTL

Abstract

Peach: Peaches [Prunus persica (L.) Batsch] are routinely chilled to increase shelf-life. Exposure to temperatures of 5° C for two weeks can induce chilling injury (CI) symptoms, including flesh mealiness (or wooliness) and a lack of juiciness. Phenotypic data were collected on seven biparental F1 peach populations maintained at the University of Arkansas Fruit Research Station. A genome wide association study (GWAS) was performed using TASSEL 5 which identified four quantitative trait loci (QTLs) associated with expressible juice, four QTLs for mealiness, five QTLs for soluble solids, and three QTLs for fruit weight. Exploiting these genetic markers could help breeders identify fruit quality traits in seedlings through marker-assisted selection (MAS).

Muscadine: Two biparental F1 muscadine (Vitis rotundifolia Michx.) populations were phenotyped for flower sex and berry color, and genotyping-by-sequencing (GBS) was performed to produce high-density genetic linkage maps. A total of 1244 SNP markers in population Black Beauty [BB] x Nesbitt [N] and 2069 SNP markers in population Supreme [S] x Nesbitt [N] were mapped to 20 linkage groups (LG) for each population. The results support previous studies revealing an evolutionary bifurcation of V. vinifera chromosome 7 into two independently segregating linkage groups in the muscadine, or, conversely, a possible fusion of muscadine-derived chromosomes into chromosome 7 of V. vinifera. The locus controlling flower type in muscadine mapped to a region spanning 4.6 – 5.1 Mbp on chromosome 2, while the berry color locus mapped to a region spanning 11.1-11.9 Mbp on chromosome 4. These high-density linkage maps lay the groundwork for marker-assisted selection (MAS) in muscadine and provide clues to the evolutionary relationship of the muscadine with V. vinifera.

Colorimetry: Precise color identification is critical in many scientific fields, and horticulture is no exception. Plant breeders must be able to effectively discern colors among plant parts and provide accurate descriptions when applying for legal protections. The RHS Colour Chart is currently recognized as the most universally accepted method of assigning color descriptions in horticulture. The RHS Colour Chart relies on manually matching plant parts with the labeled color chips provided. Color perception in humans is complicated by many factors, including the type and quantity of illumination available as well as the individual’s own physiological abilities and limitations. Scientific colorimeters have been developed to serve as an objective way to study color, and many hypothetical color space models have been created to enhance this field of study. The CIE 1976 L*a*b* (CIELAB) color space is widely recognized as a scientific standard and was used in this study. Traditional colorimeters have been bulky and expensive lab equipment, but a new, portable, inexpensive LED-based color scanner called the Nix Pro Color Sensor™ has recently become available. Multiple studies were conducted comparing the Nix Pro with the Konica Minolta CR-400 colorimeter and the RHS Colour Chart paint chip system. The results indicate the Nix Pro, which is inexpensive, yields consistent results, and features built-in color matching capabilities, could be a very useful tool for horticulturists and plant breeders.

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