Date of Award

Spring 2024

Project Type

Thesis

Program or Major

Genetics

Degree Name

Master of Science

First Advisor

Iago Hale

Second Advisor

Rebecca Sideman

Third Advisor

Kelley W. Thomas

Abstract

Kiwiberry (A. arguta (Siebold & Zucc.) Planch. Ex Miq.) is a functionally rich, grape-sized aromatic fruit crop that can tolerate cold temperatures up to -30 °C. It is a lesser-known species within the Actinidia genus that has the potential for commercialization especially in cold regions like New England owing to its smooth skin, and aromatic and intense tropical flavor. Kiwiberry is a vine crop that takes about 3-5 years to reach reproductive maturity, indicating a long breeding cycle. In addition, it is a dioecious crop that requires identification and maintenance of male and female vines in the vineyard. In this scenario, the traditional breeding process is resource-intensive for labor, space, time, and money. Instead, using molecular breeding techniques such as marker-assisted selection would effectively reduce the breeding cycle allowing the study and selection of traits related to flowering phenology, fruit attributes, nutrition, and biochemical compounds early in a breeding program.The broad objective of this research was to discover markers for genetic improvement of commercially important traits related to kiwiberry. Chapter 1, in general, highlights the importance of marker-assisted selection on kiwiberry breeding and identifies important traits related to vine growth, fruit attributes, nutrition, and anti-nutritional compounds. Among these traits, the first research objective was to phenotype an antinutritional compound; oxalate, an irritant compound found as calcium oxalate raphide crystals in both fruit tissues (pulp and skin) (Chapter 2). Since kiwiberry is eaten along with the skin, it uplifts the overall oxalate profile of the fruit. Higher oxalate intake especially the crystals can cause throat irritation and in the long run, may lead to kidney stones formation. So, two biparental mapping populations were developed with the cross of a high oxalate female line with ‘Ananasnaya’ and a low oxalate female line ‘74-8’ with a common male line ‘F7’ with an intent to create a segregating mapping population. For the first objective, I hypothesized that at least one of the mapping populations was segregated. The next objective was to understand the relationship between oxalate content in pulp and skin to identify if lowering oxalate in pulp tissue affects oxalate deposition in the skin tissue. It was identified that both populations were segregating and there was a positive relationship between pulp and skin. Next, it was concluded that pulp would be the better tissue to move forward for phenotyping in consideration of the majority of fruit being pulp and the relationship between the oxalate content in the fruit tissues. The research focus shifted with the spring freeze event on May 17th, 2023 that killed all the buds before anthesis. Inflorescence structure being an important component of yield, the next step was to discover markers associated with the mean flower numbers per cluster; also defined as floral density. Chapter 3 had specific objectives to identify markers associated with floral density and validate them in different genetic backgrounds. For the first objective, genetic linkage maps were constructed using a pseudo-backcross marker set for the female line 74-8. Then, quantitative trait loci (QTL) analysis was done to identify potential candidate markers using the linkage maps and floral density phenotypic data from 74-8/F7 population. To validate the identified potential markers; the second objective, a comparative genomics approach was taken. Actinidia eriantha genome was used to identify independent potential markers within the previously identified QTL region from the pseudo backcross marker set for the female line Ananasnaya. The bulk segregant analysis of the identified new markers was performed using phenotypic data from Ananasnaya/F7 population to confirm the marker-trait association. From this analysis, 3 markers were identified in the 74-8 pseudo backcross marker set to be associated with floral density in terminating shoots, and 10 co-located markers were identified from the Ananasnaya pseudo backcross marker set around the 74-8 pseudo backcross markers, providing preliminary validation. Although these findings are preliminary, they provide a good foundation for applying marker-assisted selection in kiwiberry breeding.

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