USDA’s Hemp Handbook Builds a Shared Genetic Resource for Research and Breeding

The U.S. Department of Agriculture is building a national hemp germplasm collection while creating standardized methods for evaluating the plant’s genetic diversity. The effort is centered at the USDA Agricultural Research Service’s Plant Genetic Resources Unit in Geneva, New York, where researchers collect, preserve and characterize hemp accessions from the United States and other countries.

The project’s primary reference is the USDA Hemp Phenotyping and Protocol Handbook. Version 4, published December 16, 2025, updates the earlier Hemp Descriptor and Phenotyping Handbook and places greater emphasis on practical protocols and research workflows.

The handbook is designed to help breeders and researchers identify accessions with useful combinations of traits, recognize gaps in the collection and improve the conservation of hemp genetic resources. It provides standardized approaches for recording plant architecture, flowering behavior, sex expression, seed characteristics, cannabinoid profiles, fiber quality, pathogens and other agronomic and biochemical traits.

Those measurements are intended to make accessions easier to compare. Data generated by the USDA-ARS Hemp Germplasm Laboratory are being added to the Hemp section of GRIN-Global, the USDA’s online system for documenting and distributing plant genetic resources. The database gives professional researchers and breeders access to passport information and characteristic data associated with preserved materials.

The USDA collection was established in 2021 as part of a broader effort to document and conserve hemp genetics after decades in which legal restrictions limited domestic research. The agency’s Hemp Germplasm Laboratory reports that its collection includes more than 600 accessions from 35 countries. The work is not simply the restoration of a single seed bank destroyed during prohibition; it is the development of a modern, documented collection with controlled regeneration and publicly accessible data.

Version 4 expands or adds protocols for several specialized tasks, including cannabinoid analysis, seed viability, seed shattering, seed-to-seed regeneration, flower induction, tissue culture and the evaluation of seed oils, fatty acids, moisture and protein. It also includes procedures for collecting feral hemp, threshing seed, cloning plants and managing fungal specimens generated through research.

One unusual part of the project addresses pollen conservation. Hemp is wind-pollinated, and its small, mobile pollen makes it difficult to maintain genetic purity outdoors. The USDA therefore studies controlled-environment regeneration and is developing practical tools and methods for collecting, preserving and distributing pollen for research and breeding.

The collection supports a basic need in crop improvement: reliable information about which genetic materials possess traits suited to particular uses. Hemp breeders may be looking for improved fiber strength, seed yield, oil composition, disease resistance, flowering behavior or consistently compliant cannabinoid levels. Standardized measurements make those traits more useful than names or informal descriptions alone.

The effort also reflects hemp’s complicated regulatory history. The USDA’s domestic hemp production rules, issued after the 2018 Farm Bill, define the regulatory framework for producing hemp and require compliance with THC testing and other conditions. The USDA-ARS collection and its handbook do not replace those production requirements, nor do they certify commercial varieties. Instead, they provide research infrastructure that can help breeders and scientists develop better-documented cultivars for fiber, grain, seed oil and other applications.

By combining preserved germplasm, controlled regeneration, standardized phenotyping and searchable records, the USDA is addressing one of the obstacles created by hemp’s long period of restricted research: a lack of consistent information about the crop’s genetic resources. The result is a foundation for more rigorous breeding and conservation, rather than a guarantee that every proposed hemp application will prove economically or scientifically viable.