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United States Department of Agriculture

Agricultural Research Service

Research Project: Acquisition, Evaluation and Conversation of Temperate Forage Legume Genetic Resources Title: Importance of gene flow to germplasm conservation and development

Author
item Greene, Stephanie

Submitted to: The Science of Gene Flow in Agriculture and its Role in Co-existence
Publication Type: Proceedings
Publication Acceptance Date: August 29, 2011
Publication Date: N/A

Interpretive Summary: Gene flow is an important evolutionary process that has contributed to the genetic diversity of our crop species. Diverse crop gene pools are a reservoir of useful traits that plant breeders rely on to meet ongoing production challenges. This reservoir of diversity is often referred to as germplasm. Gene banks conserve and make available germplasm so scientists and plant breeders can identify and deploy useful traits. The USDA National Plant Germplasm System (NPGS) manages over 542,000 germplasm accessions. A large part of our work is to increase accessions when seed numbers decline. An important objective during seed increase is maintaining the genetic integrity of original samples. This is especially critical for crops that are cross pollinated, such as alfalfa, corn and sunflower. To prevent inadvertent gene flow, accessions of cross pollinated crops are isolated by various means such as insect or pollen proof cages or bags, or separated by barriers or geographically. As GE (genetically engineered) crops come on line, germplasm collection users, both domestic and international have expressed concern that non-GE germplasm remain free of transgenes. Maintaining seed purity in alfalfa is particularly challenging, given that the species is highly out crossing, and is pollinated by insects, especially bees, which can move long distances. A second concern is the occurrence of feral alfalfa populations that may act as reservoirs for transgenes, helping to bridge the distance between GE and GE-sensitive alfalfa. Further research will help us clarify the challenges of controlling gene flow to prevent the adventitious presence of GE traits. This summer we carried out a baseline survey of feral alfalfa in California, Idaho and Washington counties that are major producers of alfalfa seed. The survey will also include Prosser, WA, where the USDA alfalfa collection is currently increased. The survey teams took extensive data on the occurrence of populations and also sampled leaf and seeds, which will be tested for the round-up ready trait. We also established a pilot project to examine the feasibility of moving the alfalfa germplasm increase program to Central Ferry, Washington, an isolated location away from alfalfa hay and seed production areas. This fall myself, and USDA, ARS colleagues Drs. Rick Boydston and Ruth Martin, and WSU Entomologist, Doug Walsh, will begin a 4 year project funded by the NIFA-BRAG program to study gene flow in alfalfa from a landscape perspective. This will provide valuable information that will support coexistence efforts within the alfalfa industry, but also support our efforts to minimize transgene flow into the USDA alfalfa germplasm collection.

Technical Abstract: Gene banks conserve and make available valuable germplasm that scientists and plant breeders can deploy to develop useful traits. The USDA National Plant Germplasm System (NPGS) manages over 542,000 germplasm accessions. A large part of our work is regenerating accessions when seed numbers decline. A central tenet in germplasm conservation is that the genetic integrity of original samples needs to be maintained during seed storage, increase and cleaning. This is critical for crops that are cross pollinated. To prevent inadvertent gene flow, accessions of cross pollinated crops are isolated using insect or pollen proof cages, or separated by barriers or geographically. As GE (genetically engineered) crops come on line, germplasm collection users, both domestic and international, have expressed concern that non-GE germplasm remain free of transgenes. Maintaining seed purity in alfalfa (Medicago sativa subsp. sativa) is particularly challenging. The species is highly outcrossing, and is pollinated mainly by species of hymenoptera, which can travel long distances. Feral alfalfa populations can also occur, which may act as reservoirs to support transgene flow. Further research will help us clarify the challenges of controlling alfalfa gene flow to prevent the adventitious presence of GE traits. This summer we carried out a baseline feral alfalfa survey. We used a spatially balanced survey design implemented in ARC GIS 10. Surveys were conducted in California, Idaho and Washington counties that are major producers of alfalfa seed. Extensive data on the occurrence of populations was taken, and leaf and seeds were sampled. Collected tissue will be tested for the round-up ready trait using RUR Test Strips (Sdix, MO. USA), and positives confirmed using event-specific PCR tests. A pilot project was carried out to examine the feasibility of moving the alfalfa germplasm increase program to Central Ferry, Washington, which is located on the Snake River, isolated from alfalfa hay and seed production areas. This fall myself, and USDA, ARS colleagues Drs. Rick Boydston and Ruth Martin, and WSU Entomologist, Doug Walsh, will begin a 4 year project funded by the NIFA-BRAG program to study gene flow in alfalfa from a field and landscape perspective. Our objectives are (1) to examine how leaf cutter and alkali bees transmit RRA across fields and how that affects harvest strategies to separate seed for non AP sensitive and AP sensitive markets; (2) to characterize feral and feral-RRA hybrid alfalfa in roadsides, orchards, vineyards and near irrigation canals for fitness parameters such as seed production, seed dormancy and viability, longevity in the seed bank, seedling establishment and plant persistence to determine how important and to what extent control strategies are required; (3) to track RR transgene flow from RRA hay and seed production fields into feral alfalfa to understand the role feral alfalfa plays as a transgene reservoir and conduit for long distance transgene dispersal; (4) to study the transmission of the RR transgene from RRA hay fields to conventional seed fields to refine isolation distances by taking into account distance and landscape variables. This will provide valuable information that will support coexistence efforts within the alfalfa industry, but also support our efforts to minimize transgene flow into the USDA alfalfa germplasm collection.

Last Modified: 12/21/2014
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