Citrus Shoot Tip Cryopreservation
Gayle M. Volk, USDA-ARS National Laboratory for Genetic Resources Preservation, 1111 S. Mason St., Fort Collins, Colorado 80521<EMAIL_ADDRESS>Robert Krueger, USDA-ARS National Clonal Repository for Citrus and Dates, 1060 Martin Luther King Blvd., Riverside, California 92507.
Brittany Moreland, USDA-ARS National Clonal Repository for Citrus and Dates, 1060 Martin Luther King Blvd., Riverside, California 92507.
Remi Bonnart, USDA-ARS National Laboratory for Genetic Resources Preservation, 1111 S. Mason St., Fort Collins, Colorado 80521.
Ashley Shepherd, USDA-ARS National Laboratory for Genetic Resources Preservation, 1111 S. Mason St., Fort Collins, Colorado 80521.
Outline
- Introduction to the USDA National Plant Germplasm System Citrus collection
- Introduction to the citrus shoot tip cryopreservation procedure
- Harvesting and preparing budwood
- Cutting nodal sections of budwood
- Surface sterilization
- Shoot tip excision
- Shoot tip processing and liquid nitrogen exposure
- Long-term storage
- References
- Additional information
- Acknowledgments
The citrus shoot tip cryopreservation procedure is available to download here.
1. Introduction to the USDA National Plant Germplasm System Citrus Collection
Access to diverse citrus genetic resources is critical for breeding new citrus cultivars that yield more and have higher quality fruit with improved resistance to pathogens and to changing environmental conditions. The USDA-ARS National Plant Germplasm System (NPGS) maintains a very diverse collection of about 600 pathogen-tested accessions of citrus under protected screenhouse conditions at the National Clonal Germplasm Repository for Citrus and Dates (NCGRCD) in Riverside, California (Video 1). Additional non-pathogen-tested accessions are maintained in cooperation with the University of California, Riverside. Many of the accessions within the NPGS citrus collection are disease-free and available to scientists worldwide for citrus research and for the development of new cultivars. The collection is backed-up in greenhouses at the University of California, Riverside, but is still somewhat susceptible to extreme weather, pests, pathogens, vandalism, etc. because trees are kept in pots within vulnerable greenhouses and screenhouses. Consequently, the pathogen-tested citrus collection is being cryopreserved for long-term security back-up at the National Laboratory for Genetic Resources Preservation (NLGRP) in Fort Collins, Colorado.
This chapter describes the process that enables cryopreservation of citrus shoot tips.
Video 1. Robert Krueger, curator of the NPGS citrus collection, provides a video-introduction to the collection.
2. Introduction to the citrus shoot tip cryopreservation procedure
The citrus shoot tip cryopreservation procedure has many steps that will be described and demonstrated. It starts with the harvest of budwood from screenhouse plants in the USDA National Plant Germplasm System genebank in Ri