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The beer industry has grown steadily in the United States over the past decade, thanks in large part to the growing popularity of craft breweries. This growth is expected to continue with an estimated market value of $146 billion by 2025. To meet growing demand from beer lovers, breweries need a steady supply of the three main ingredients in beer: barley, hops and yeast.
Sarah Carey, a postdoctoral fellow in the Department of Crop, Soil, and Environmental Sciences at Auburn University’s College of Agriculture, recently received a $225,000 two-year postdoctoral fellowship from the U.S. Department of Agriculture. Agriculture of the National Institute of Food and Agriculture, or USDA NIFA, to develop genomic tools to sustainably accelerate hop breeding programs. Carey also works for the HudsonAlpha Institute of Biotechnology in the laboratory of Alex Harkesassistant professor in the Department of Crop, Soil, and Environmental Sciences and researcher on the faculty of HudsonAlpha.
Although the United States is the world’s second largest producer of hops, most hops are grown in the Pacific Northwest due to the temperature and climate requirements of today’s hop varieties. Globally, hop production in 2020 increased by more than 1,100 hectares, or approximately 2,056 American football fields. In an effort to increase hop production to satisfy all hopped beer enthusiasts, scientists and breeders are trying to create new varieties of hops that can grow across the United States.
Marrying genomic technology, traditional breeding
Hops are the flowers, or cones, of a plant called Humulus lupulus. The glands inside the hop cone produce bitter acids and other essential oils which are important in helping to keep beer fresh longer and helping beer retain its head of foam. However, one of the most popular attributes of hops is to add a “hoppy” aroma, flavor and bitterness to beer. Hops are very sensitive to their environment and can only be grown on a commercial scale in certain regions of the country.
In addition to their limited geographic footprint, hop cultivation is also complicated by the fact that only female plants develop economically valuable hop cones. The male plants are needed for breeding purposes but should be separated from the females in the field so that they do not fertilize the female plants, causing unintended crossbreeding and seed production which negatively affects the flavor profile of the beer. Using traditional breeding methods, breeders must wait up to two years to determine if a given plant in the field is male or female.
One way to improve the hop industry is to identify sex-determining genes to better control the sex of the plant. However, few hop varieties have had their genome sequenced to the level and quality necessary to study sex chromosomes. The Carey fellowship project aims to create high-quality, fully-chromosomely assembled reference genomes for the five H. lupulus varieties.
Reference genomes and other genomic tools developed during Carey’s fellowship will help identify genetic markers of sex determination, allowing plant breeders to identify the sex of plants earlier. Early identification of male plants would reduce water and land use and allow more female plants to grow. The tools will also allow breeders to identify genetic markers of other valuable traits like drought tolerance and pest resistance.
“This scholarship gives me the opportunity to take the skills I learned studying mosses and evolutionary genetics in graduate school and apply them to an agricultural crop,” Carey said. “By doing this work at HudsonAlpha, I will also be immersed in cutting-edge genomics that I can combine with my current skills to create a hop breeding pipeline that is directly useful to the botanical and agricultural world.”
A pipeline to create regional hops
Carey already intends to use the genomic resources she is developing over the next three years to create a hop from Alabama. She and the Harkess lab collaborated with Auburn researchers, like André da Silva’s lab, to begin the process of growing hops in Alabama, a state that sits outside of most people’s environmental comfort zone. hop varieties. They plan to breed different varieties to make different genetic crosses, building on hop genomes and genetic markers from Carey’s project to establish hop varieties that can grow in the climate and environment here in Alabama.
“Sarah has built a powerful network of collaborators and stakeholders that encompasses industrial, academic, agronomic and biotech partners to come together to grow a new crop in a new place,” Harkess said. “Hops grow in an extremely limited geographic region, complicated by its unique reproductive biology and sex chromosomes. Sarah approaches these issues from a different perspective, taking advantage of the immense diversity of hop species, the evolutionary histories of these species, and her unique skills in assembling complex plant genomes and sex chromosomes.
As part of her fellowship, Carey also plans to create the Southeastern Hop Alliance to build a community of hop scientists, breeders, brewers, and other hop industry stakeholders. Carey hopes to hold symposia at Alabama breweries to bring alliance members together and provide updates on genome references and tutorials on using the tools she’s building. From this community, Carey aims to learn the many facets of hop breeding and the hop industry to better develop genomics tools for the needs of the people who actually use them.
“I am so grateful for the opportunity the USDA NIFA Postdoctoral Fellowship gives me,” Carey said. “I’m learning about hop breeding from an academic, non-profit, and industry perspective, while learning the ins and outs of developing high-quality genomics toolkits. The end result, from the point From a scientific perspective, will be genomics tools that will help accelerate hop breeding programs. But from a personal perspective, this fellowship will give me the skills I need to launch my career in plant genomics to new heights. exciting.
Key collaborators contributing to the Hops Genome Project include Joshua Havill, PhD candidate at the University of Minnesota-Twin Cities; Gary Muehlbauer, McKnight University Professor Emeritus at the University of Minnesota-Twin Cities; Katherine Easterling, Principal Investigator and Hopsteiner; Paul Matthews, Principal Investigator and Hopsteiner; and da Silva.
To hear Carey talk more about his research on hops, listen to this episode from the HudsonAlpha podcast Small shipments.