Master of Science, The Ohio State University, 2019, Horticulture and Crop Science

U.S. black raspberry (BR) production is currently limited by narrowly adapted, elite germplasm. Improved understanding of genetic control and stability of pomological traits will inform the development of improved BR germplasm and cultivars. To this end, analysis of a multiple-environment trial of two BR mapping populations derived from crosses of commercial cultivars with wild accessions has provided insights into genetic variation, genotype-by-environment interactions (GEI), quantitative trait loci (QTL), and QTL-by-environment interactions (QEI) of fruit quality traits among diverse field environments. Genetic components and stability of four fruit size traits and six fruit biochemistry were characterized in two mapping populations following their evaluation over three years at four distinct locations representative of current U.S. BR production. GEI of pomological traits were described using two methods: mixed model analysis and Bayesian Finlay-Wilkinson regression. Both methods revealed relatively stable genetic control of the four fruit size traits across the tested production environments and less stable genetic control of the six fruit biochemistry traits. Further, Finlay-Wilkinson regression revealed individuals contributing to GEI for each trait. Ten QTL associated with three fruit morphology traits and five QTL associated with two fruit biochemistry traits were identified. Of the fifteen total QTL, eleven exhibited significant QEI. Closely overlapping QTL revealed linkage of several fruit size traits: fruit mass, drupelet count, and seed fraction. Further, alignment of linked markers to the BR genome revealed genomic regions associated with these traits. These and related findings are expected to guide further genetic characterization of BR fruit quality, management of breeding germplasm, and development of improved BR cultivars for U.S. production.

Committee: Jonathan Fresnedo Ramirez (Advisor); Leah McHale (Committee Member); Joseph Scheerens (Committee Member) Subjects: Genetics; Horticulture

Master of Science, The Ohio State University, 2017, Horticulture and Crop Science

Root systems are known to have profound influences on nearly every aspect of plant development and biology, including vegetative and reproductive capacity. However, the specific impacts of intra-specific combinations of root and shoot systems, when combined in physical hybrids, on important physical, chemical, and sensory properties of Capsicum annumm pepper fruit are largely unknown. Grafting was used to combine the canopy and root system of two types of Capsicum plants (producers and non-producers of capsaicin and small, more elongated versus large, blocky fruit), thereby making it possible to examine the separate and combined roles of variety-specific roots and shoots in shaping key fruit characteristics, among them the concentration of capsaicin. Capsaicin is an ideal metabolite to study root-shoot interaction and roles because early stages of its biosynthetic pathway occur in the roots, with final assembly in the fruit at advanced stages of development. Fruit size, shape, wall thickness, and soluble solids levels were similarly tracked as they and capsaicin influence consumer acceptability and fruit marketability. The overall program involved field studies in 2016 and 2017, a targeted wintertime greenhouse study, and consumer sensory analysis. Overall, it was found that the Capsicum variety supplying the root system of the grafted plant had little influence on the variables measured when a sweet pepper was used as a scion. When a hot pepper was used as a scion the root system played a large role in influencing the capsaicinoid profile of the fruit. Implications of this finding include: a) that the variables measured are influenced by more than the root systems used here and b) that it may possible to employ rootstock-scion combinations without concern over rootstock influence on fruit in commercial production.

Committee: Matthew Kleinhenz (Advisor); Joseph Scheerens (Advisor) Subjects: Biology; Botany; Food Science; Horticulture