Assessing the genetic diversity of ten camellia taxa

Darfler, Joshua H. L.
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University of Delaware
Camellias have been cultivated for centuries beginning in ancient China, and have become important worldwide for both ornamental and economical reasons. The genus is the largest within the Theacea , and has been estimated to consist of 100-300 different species. Ornamental species of camellias have been growing at Longwood Gardens since the founding of the estate by Pierre S. du Pont, and were in fact one of the first species to be planted in the conservatory upon its completion in 1921. When Longwood Gardens became a Public Horticulture Institution, the first director identified camellias as one of the target genera for the newly created research department, with the goal of breeding new cultivars of camellias that were consistently cold hardy in the region, and could be used for outdoors display. Today camellias are still a focus for the Longwood Gardens Research Department, and several cultivars have been released that exhibit exceptional cold resistance in the area. Breeding practices, however, have drastically changed since the founding of the camellia-breeding program at Longwood Gardens in the late 1960s. New technologies allow for the quick and efficient analysis of genetic material in order to better understand the genetic diversity of species, and to allow breeders to screen prospective new parent lines for their use in future crosses. This research focuses on three such technologies - DNA analysis, next-generation RNA sequencing (RNA-seq), and flow cytometry - and assesses their feasibility for future use with Longwood Gardens' research program. A group of ten Camellia species was selected as an initial sample, and additional camellia cultivars were included when possible. This research showed that DNA and RNA sequencing could provide deeper insight into the relatedness of different camellia species, and if desired this research could be expanded to include more Camellia species from the Longwood camellia collection. This genetic analysis, however, requires specialized equipment, which may prove to be a large financial investment with potentially small practical returns. The use of flow cytometry, however, could prove to be very beneficial for Longwood Gardens, allowing breeders to quickly assess the genome size of camellia accessions and to potentially screen seedlings for hybrid genome sizes. Furthermore, flow cytometry has a much lower initial startup cost, which could even be potentially avoided by renting time on the flow cytometer located on the University of Delaware's campus. Results from this study can be used to guide Longwood Gardens as they move forward with the camellia-breeding project, and provide insight into some of the pros and cons of different genetic analysis technologies. Furthermore some results can be immediately be used to direct breeders in their selections of new species to include in and exclude from future crosses.