Under First Lady Michelle Obama, the White House kitchen garden has been expanded and reinvigorated to include a wide range of herbs, fruits, and vegetables. It serves to educate people, especially children, on the importance of good nutrition and the role that vegetables and fruits can play in improving health. The sweet potatoes that were planted in the garden were provided by North Carolina State University (NCSU) and include Covington, a variety developed at NCSU…
The genus Cercis, commonly known as redbud, is a valuable commodity to the landscape industry in North America and can be found growing in numerous regions across the globe. Cercis consists of approximately 10 species, often cultivated as medium sized trees or shrubs possessing a variety of interesting morphological characteristics. Careful examination of these traits and how they are inherited can help plant breeders better understand the genetic mechanisms that lead to specific phenotypes and allow for a greater degree of control while manipulating these characteristics in future breeding programs. David Roberts thesis involves three major areas of research; examining the genome size of more than 30 Cercis taxa, determining chlorophyll and carotenoid concentrations in the leaf tissue of yellow leaf Cercis cultivars and investigating the modes of inheritance for various morphological traits found in select Cercis cultivars.
Most recently, David Roberts completed a working draft of my inheritance study, which documents several intriguing occurrences within our populations of interest. This study was possible thanks to the extensive breeding populations of Cercis previously established by Dr. Dennis Werner. Dr. Werner’s impressive collection of Cercis has allowed research modes of inheritance that underlie numerous ornamental phenotypes including weeping architecture, purple leaf color, gold leaf color and variegated leaf type. Characteristics like purple leaf color and weeping architecture have proven to be the result of recessive traits, inherited in a simple Mendelian fashion while the variegated phenotype of C. ‘Floating Clouds’ can be attributed to maternally inherited genes. The most challenging (and interesting) aspect of Mr. Roberts research so far, has come from investigating the inheritance of a gold leaf cultivar, C. ‘Hearts of Gold’. It was originally hypothesized that the gold leaf color found in C. ‘Hearts of Gold’ was simply inherited and recessive in nature. However, F2 plants derived from C. ‘Covey’ (green leaf, weeping habit) x C. ‘Hearts of Gold’ (yellow leaf, upright habit) do not fit any known segregation ratio and exhibit unexpected phenotypes. In addition, an unusually high number of albino mutants were recovered from the F2 progeny of this cross. Interestingly, when the albino mutants and gold leaf mutants were combined into a single category (yellow), 10 out of 13 families fit a 3:1 ratio for green leaf : yellow leaf phenotypes (P<.05). While the exact reason behind this distortion in segregation is unknown, one possible explanation could come in the form of transposons. A large number progeny recovered from crosses involving C. ‘Hearts of Gold’ demonstrate a type of unstable variegation that is often attributed to transposon activity (fig. 1). While the transposon theory might explain how the unexpected phenotypes occurred, it does not adequately explain the high proportion of albino progeny. The most likely explanation is that the gold-leaf trait in Cercis is polygenic in nature and that through recombination, lethal mutations occur at a relatively high frequency. One of the most mysterious aspects of my research has also proven to be one of the most educational. David Robers quandary has led to discussions with professors of not just horticulture and genetics but crop science, plant biology and forestry as well. While Mr. Roberts does not currently (and may never) have an explanation for this phenomenon, trying to fit the pieces of this puzzle together has been a truly enlightening experience.
After months of planning, the cuttings arrived in July and another year in the North American Poinsettia Trials was started. The Trials are a cooperative effort with Jim Barrett and Paul Fisher at the University of Florida and Wayne Brown at the Vineland Research and Innovation Centre in Ontario. Homewood Nursery and Garden Center, in north Raleigh also participates, bringing a commercial perspective to the Trials. This Trial program has been evaluating poinsettias, in cooperation with the poinsettia breeder companies, for 21 years since it was started in 1993.
This year we had 113 poinsettia cultivars from five suppliers to grow and compare, including 16 new cultivars and 19 experimental cultivars representing the latest in breeding efforts and future introductions. We had two main trials: One in which the cuttings were all planted at the same time and grown without plant growth regulators (pgr). In the other trial the planting date and pgr applications were varied to produce a managed crop that was as uniform in height as possible across all cultivars. We had a number of other smaller trials and experiments this year as well. We host two open houses to show all of the cultivars and research to growers and the general public.
One of the most distinctive new varieties, Princettia, is a hybrid between the traditional poinsettia, Euphorbia pulcherrima, with red bracts and a wild species, Euphorbia cornastra, with white bracts. The Princettias had brilliant white, pink and red bracts (see photo at left).
It is with regret that we say goodbye to departmental computer technician, Paul Stanley. Paul graduated this semester and has taken a position with Google. He has been a tremendous help to the department and we wish him well in the next chapter of his life.
Please join us in welcoming Luis Duque and Amber Harmon to the department. Both will be working with Craig Yencho, Luis as research associate and Amber as research technician.
In September, Rebecca Dunning of CEFS joined the faculty as a research assistant professor and George Allen, research associate professor, retired. Post-doc Shingo Nagaya left NC State, and post-doc Tara Nash will complete her program in December.
It is with pleasure that we note our own Brad Thompson graduated with his master’s degree in December and will continue to work with Jonathan Schultheis and his program. Congratulations!