Jonathan Mahoney is a Visiting Research Fellow at the Arnold Arboretum and a recipient of the Deland Award for Student Research. Learn more about his work breeding the next generation of antioxidant-rich fruits in this interview for ARBlog.
What are you studying at the Arnold Arboretum?
I’m studying applied plant breeding of Aronia (chokeberry), whose fruits are highly beneficial for human consumption. It’s a deciduous shrub native to eastern North America. Right now, chokeberry’s place in commercial fruit production and the nursery trade is small. This is largely because although the health benefits of eating Aronia are enormous, the fruit is also very high in tannins and very astringent, so it needs to be processed before eating to make it palatable. The objective of my research is to use hybridization between different plant genera to improve the quality of Aronia fruit and select for desired traits, so that we can breed a better-tasting Aronia fruit with all the same health benefits.
Another thing I’m looking at is the huge lack of genetic diversity in Aronia production––there are only a handful of species in the genus. As we know from history, a monoculture (severe lack of genetic diversity) can set up society for catastrophes like the Irish potato famine. Low genetic variation makes plant populations more vulnerable to changes in the environment such as climate change, pests, and diseases. In this case, when a potato disease struck Ireland in the 1840s, this crucial crop was devastated, along with the society that depended on it. If there had been more variation among potatoes at the time, the disease might not have had such an enormous impact on the country’s crops and economy.
With Aronia, we are looking at intergeneric hybridization to increase the genetic diversity as well as develop a better fruit for eating. Crosses with other fruits such as apples and pears may prove to produce better fruit taste, or other qualities of interest for commercial growers. Of course, intergeneric crosses are not at all simple or easy to facilitate. The first question I have to ask in my research is, “Can we make these crosses at all?”
In order to understand the possibilities with hybridization, we first have to study the mating compatibilities of the genera we want to breed. This is where my work at the Arboretum’s Weld Hill Research Building becomes key. Genetic incompatibilities can occur at different stages of the reproduction process, and exist to prevent inbreeding and hybridization between certain relatives. Understanding the genetic incompatibilities that exist between hybridizations will help our breeding program make informed decisions involving hybrid crosses. To further investigate these mating systems, I’m using microscopy to examine the sexual reproduction process between hybridizations. Another example of a mating barrier is how certain plants flower at different times. We can overcome this type of mechanism by synchronizing flowering time––collecting early flower pollen and using it later on to make crosses with later-flowering plants.
What do you find most compelling or unexpected about your research?
Recently, we managed to cross ×Sorbaronia dippelii from the Arboretum with pear. We didn’t know if the cross would work, so we were really excited when we were able to regenerate seed in-vitro. However, as it turns out, we ran into a barrier called hybrid lethality that occurs in many hybrids between distant relatives. It involves some interaction between pathogen-resistant proteins, and results in the plant looking like it’s infected by pathogens. This was an unexpected and disappointing setback, because we thought we had these hybrid seedlings successfully growing. From a different perspective, though, it was also an interesting development, and posed a new question for us to investigate: what is the mechanism behind hybrid lethality and how can we overcome the barrier? So now we are trying other techniques to see what might work. There’s always something unexpected, but I think the compelling thing is turning the challenges into new questions, and the fact that there are always new questions.
What is the most challenging aspect of your work?
One challenge is that plants can be difficult colleagues to work with. They don’t take the weekends off. You have to plan your time around your research; the plants become a part of your life. It can be very difficult, say, in the spring when we’re trying to make controlled pollinations, and we are trying to synchronize flowering between different plants. Another challenge that can actually be fun is the fact that we are studying non-model organisms (organisms that have not already been thoroughly explored or researched), which is something a lot of scientists at the Arboretum do. It’s challenging to work with plants that have very little information available regarding their genetic makeup. It certainly makes you think differently about your research.
Who or what influenced you most in pursuing science as a career?
I’ve always been interested in the natural world. I worked in a greenhouse throughout high school and as an undergraduate I had internships at the USDA-National Plant Germplasm System and Cornell University. I had wonderful mentors during my undergraduate studies at Iowa State University in the Department of Horticulture who inspired me to continue on to graduate school research. Though I started out learning about plant science and horticulture, the research side of things became more intriguing during my time at Iowa State. There was a particular plant physiology class that hooked me in and got me interested in the details of plant biology. Lastly, my parents and family have always been very supportive of my graduate studies and research career.
What makes the Arboretum a good fit for your study?
The Arnold Arboretum offers a tremendous amount of resources for scientists. Of course, the genetic diversity of the Living Collections is a big draw. My lab at UConn [University of Connecticut] has been using material from here for the past decade. It’s been a terrific resource for our breeding work. At Weld Hill, the top-of-the-line equipment is a huge plus, of course, but what I have found to be truly inspiring are the people here. I can talk to other visiting scientists, Faye [Faye Rosin, Director of Research Facilitation], or Ned [William (Ned) Friedman, Director of the Arnold Arboretum] and get their expertise or learn about an area that I’m not as familiar with.