AgEBB-MU CAFNR Extension
Green Horizons
Volume 24, Number 2
Spring 2020
Participatory Chestnut Breeding:
Creating a Participant Network to Characterize Genetic Diversity
and Grow the Midwest Chestnut Industry
Ron Revord and Michael Gold
Over the past 25 years, U.S. chestnut cultivation for nut production has increased through grower-led advancement. In the Midwest, a predominant reason for this growth is the long-standing, steady progress made by exceptionally dedicated growers and the University of Missouri Center for Agroforestry partners to develop regional markets. Grassroots chestnut production over the past decade has led to the successful establishment of multiple farmer cooperatives (e.g., Michigan, Ohio, Iowa) and many new regional markets in the Midwest. Multiple years of market research indicate that annual demand exceeds supply (Gold et al. 2006; Gold and Cai 2019) and that chestnut cultivation must expand accordingly. In fact, the number of chestnut farms in the United States grew by 57 percent from 2012 to 2017, hundreds of which are now approaching mature bearing years including over 400 new chestnut farmers in midwestern and neighboring states (NASS, 2017).
In the late 1990's, the University of Missouri's Center for Agroforestry initiated an extensive germplasm collection and evaluation effort for Chinese chestnut (Castanea mollissima) and interspecific hybrids (Mori et al. 2018). The majority of chestnut orchards in the region are primarily comprised of half-sibling seedling families from open-pollinated Chinese chestnut cultivars, with unknown local performance specificity needed for long-term success. However, these plantings can contribute to the identification of superior trees that have recombined desirable traits and improved adaptability (Miller, 2003; Anagnostakis, 2012). Currently, there are more than 7,000 chestnut seedlings of bearing age (representing 20 half-sib families) on farms in the Midwest.
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Roger and Kay Smith |
Presently, each of several Midwestern states are annually producing tens of thousands of pounds of chestnuts that meet the high-grade standards for local markets. All of this production is sold out within two months of harvest (typically within weeks). Growth in demand continues to outpace supply, even as mature orchards and plantings expand. In 2018, Iowa growers (68) took 40,000 lbs. of high-grade chestnut to market through the Prairie Grove Growers cooperative. Production capacity from 59 individual Missouri growers ranges upwards from 10,000 lbs. In Ohio, growers of the Route 9 Cooperative have steadily increased production to 100,000 lbs. with 75 farms of bearing age. Similar trends have been observed in a half dozen other states in or neighboring the Midwest. All of these states have a roughly equal number of young, non-bearing orchards, increasing the number of bearing farms from 330 to over 600.
The economic success of chestnut as a tree crop is dependent upon consistent yields and high nut quality, both complex traits. In general, Chinese chestnuts have desirable nut characteristics, including a round shape and preferable size (12 g), a detachable pellicle, and widely loved flavor and texture. This species also has good to superior blight resistance, excellent phytophthora resistance, and cold hardiness. However, Chinese chestnut yields are half that of the Euro-Japanese hybrids, which are favored in low frost areas such as California and parts of Europe. Now, the breeding need for chestnut is to identify and combine desirable attributes into an elite group of superior parents with known combining ability, while expanding the genetic base to increase stress resistance and minimize nut defects. Thus, there is a need to systematically identify exceptional individuals in the expanded on-farm gene pool.
This year, the University of Missouri Center for Agroforestry, in collaboration with the University of Notre Dame and several grower partners, received a 3-year, $923,155.00 grant from the USDA Specialty Crop Multi-State Program to respond to this need by creating a participant network to characterize genetic diversity of superior on-farm germplasm and support the growth of the Midwest chestnut industry. The project team will formalize a participatory network of chestnut growers to characterize on-farm germplasm and assemble sets of superior selections.
The main objectives of this project are to:
- Develop a database of on-farm chestnut germplasm in the Midwest;
- Expand the genetic base of Phytophthora root rot resistance in Castanea germplasm;
- Characterize the phenotypic diversity of top database selections; and
- Characterize the diversity, parentage, and ancestry of the database selections.
Building genetic improvement efforts from this pre-existing material capitalizes on decades of farmer investments and evaluations, and creates an opportunity to assemble the improved genetic base necessary to establish a dedicated breeding program that can support future growth of the Midwest chestnut industry.