Breeding a Better Berry

Tuesday, October 23, 2012
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Last summer, the second-generation hybrid strawberry plants that were grown from seed at the University of New Hampshire (UNH) became top performers for a local grower. “Randy Warren told us they were the healthiest and most vigorous plants he’s ever had,” says Tom Davis, Professor of Plant Biology and Genetics in the College of Life Sciences and Agriculture (COLSA) at UNH. Davis has been immersed in multi-institutional research on the genome of this New England and international favorite for the last six years, with the aim of adding sophisticated DNA fingerprinting and computational methods to the plant breeder’s toolbox.

Davis and his Ph.D. student, Lise Mahoney, embrace plant breeding as a tasteful art that integrates science and aesthetics.  Working together at the New Hampshire Agricultural Experiment Station (NHAES), their aim is to develop new varieties that will meet the changing needs of growers in the region while addressing consumer demands for high quality, locally grown produce and value-added horticultural products.  

Davis and Mahoney are especially excited about the newly acquired strawberry genome sequence that enables them to develop tools for marker-assisted breeding. “It’s an approach that takes advantage of the DNA fingerprints of the plants to predict what their characteristics will be,” says Davis about this multidisciplinary aspect of his research that expands his capabilities. “We are trying to generate the kinds of basic knowledge about strawberry genes and genetics and strawberry germplasm that can be used to more effectively breed strawberries.” Davis and Mahoney maintain thousands of strawberry plants at the Woodman Farm and in the Macfarlane Greenhouse for their studies. These facilities, operated by the NHAES, are an invaluable asset to their resource intensive research.

NHAES Faculty Fellow and Professor of Biology, Anita Klein, understands the challenges involved in breeding the strawberry plant. “Strawberry is an extremely difficult plant to breed because it is an octoploid, having eight chromosome sets instead of the usual two. Also, strawberry varieties are propagated vegetatively,  – break off a runner and root it,” says Klein. “The problem is that over many generations, these vegetatively propagated plants build up a load of pathogens. By using a marker-aided breeding approach, Davis and his colleagues might be able to break this cycle of being stuck with vegetatively propagated materials.” 

In addition to selecting plants with higher disease resistance, Mahoney has gained expertise in identifying molecular markers – or DNA features – which are associated with other traits that she and Davis are interested in breeding into their plants. With the goal of becoming a commercial plant breeder after graduation, Mahoney says, “I’d like to breed strawberries with excellent fruit quality and disease resistance, which are long bearing and locally adapted to the Northeast.” Mahoney is also introducing beautiful flower colors into some of her strawberry breeding lines, including shades of dark red and lavender.

In addition, Davis and Mahoney are working with DNA fingerprinting in association with the United States Department of Agriculture’s (USDA) RosBREED Project. “The research is conducted on crops in the Rosaceae family, such as tart cherries, peaches, apples, strawberry. We’re concentrating on the strawberry component, along with other universities that are also doing research in strawberries and breeding,” says Mahoney. “With that project, about 1100 different strawberries will be genotyped – DNA fingerprinted – and also phenotyped, which is the traits description. We will then analyze the resulting database to associate traits with specific DNA fingerprints, which becomes a great predictive tool for our program.” Mahoney’s particular passion is the pigments in the strawberry fruits – the anthocyanins – and the DNA markers of those anthocyanins that are also associated with antioxidant values.

Davis undergirds the newly acquired genomic information with many years of basic research findings on the genetic diversity of wild and cultivated strawberries. During that time, he’s educated undergraduate and graduate students, trained postdocs, collaborated with international scientists, and published a series of papers on the topic. Together, Davis and Mahoney are developing a plant breeding program in response to changing circumstances and opportunities, which will enable them to continuously develop adapted and productive varieties. “Plant breeding is a moving target,” says Davis, to which Mahoney adds. “It’s continuous improvement.”