Optimizing regeneration protocols for native Seeds of Success—collected milkvetch (Astragalus spp.) genetic resources

Authors: Hallwachs, Bailey; MARTIN, ELIZABETH - Lewis And Clark State College; HELLIER, BARBARA - Retired ARS Employee; Irish, Brian

Submitted to: Native Plants Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2025
Publication Date: 6/16/2025
Citation: Hallwachs, B.S., Martin, E., Hellier, B., Irish, B.M. 2025. Optimizing regeneration protocols for native Seeds of Success—collected milkvetch (Astragalus spp.) genetic resources. Native Plants Journal. 25(3):179-191. https://doi.org/10.3368/npj.25.3.179.
DOI: https://doi.org/10.3368/npj.25.3.179

Interpretive Summary: The USDA ARS National Plant Germplasm System (NPGS) holds extensive collections of diverse plant species native to the United States. A large proportion of these are wild relatives of crops that contribute to the genetic diversification in U.S. agricultural production. Unlike crop species, many of these collections lack basic information on how to germinate and produce seed which are critical for long-term conservation. Milkvetches are important native forage legume and restoration species in the Western U.S., are well represented in the NPGS collections, and lack essential management information. In this research protocols for successful germination, field establishment, identification of ideal pollinator and to produce sufficient quality seed were developed for a subset of native milkvetch species. Protocols developed will increase efficiencies in how milkvetches are conserved and managed long-term in the collections and could also be applied in larger-scale production of native seed commercially.

Technical Abstract: The USDA ARS National Plant Germplasm System (NPGS) conserves and promotes the use of important agricultural and ecological plant genetic resources and their associated information. Within the NPGS collections of ~600,000 accessions, a subset of over 23,000 representing 147 plant families, have been acquired though the Bureau of Land Management (BLM) Seeds of Success (SOS) program. Many of these taxa lack basic biological information (e.g., germination/pollination biology) critical to seed regeneration and long-term germplasm conservation. To address knowledge gaps, we used five native milkvetch (Astragalus L. [Fabaceae]) species two-to optimize germination protocols, characterize phenological and phenotypic traits, and test pollinator efficiency using managed and naturally occurring pollinators. Germination trials tested three cold stratification (0, 2, or 6 weeks in 4°C (40°F) cold storage) and two germination temperature, (low: 15/25°C [59/77°F] and high: 20/30°C [68/86°F] treatments in a full factorial design in a germinator, successful germinates were used in field trials. Optimal pollination method (honeybee (Apis mellifera Linnaeus [Apidae]), alfalfa leaf cutter bee (Megachile rotunda Fabricius [Megachilidae]), and open pollination) were tested in the field. Plants were transplanted in a randomized complete block design to two sites (Prosser and Pullman, WA) in the fall of 2020. A. drummondii had significantly higher germination for both accessions and temperature treatment levels compared to the (A.canadensis, A. lentiginosus, A. lonchocarpus). Only A. canadensis L. and A. bisulcatus had sufficient survival to move forward with pollinator treatments. Statistically significant differences were not found in pollinator treatments for seed set or yield (p>0.05). A. canadensis seemed to perform generally better than other species with the highest number of established and surviving plants, good seed set, and highest seed yields. This research provides needed information that can be used in the active long-term germplasm management of these milkvetch species and points to the need for further research on protocols to safeguard these important plant genetic resources.