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Poster: Biology & Disease Mgmt: Integrated Pest Mgmt


Cryotherapy and Mini-plant Biological Indexing: New Tools for use in Citrus Clean Stock/Certification Programs
C. RAMADUGU (1), M. Keremane (2), G. Volk (3), J. Hartung (4), G. McCollum (5), R. Lee (2) (1) University of California Riverside, U.S.A.; (2) USDA ARS National Clonal Germplasm Repository for Citrus and Dates, U.S.A.; (3) USDA ARS National Center for Gen

Shoot tip grafting (STG) followed by biological indexing using 10-14 month old indicator plants has been the mainstay for eliminating graft transmissible pathogens (GTP) from citrus accessions. We report the application of cryotherapy (freezing vegetative buds in liquid nitrogen followed by grafting onto seedling rootstocks) as an alternate, effective method for the elimination of certain GTPs. Because larger vegetative buds are used for cryotherapy, up to 1.5 mm, as compared to 0.1 mm of apical meristem buds used for STG, personnel become proficient after 1-2 weeks of training as compared to 6-12 months training needed for STG. We also have developed a biological indexing method using very young (mini) indicator plants, 60-90 days old. Side by side comparisons of 30 accessions using traditional and mini-plant biological indexing indicate the same level of sensitivity between the two methods. The use of mini-plants for biological indexing requires much less time and greenhouse space, also GTP requiring cooler temperatures to produce symptoms may be indexed year-round by placing the mini-plants near the cooling pads in summer. The use of cryotherapy and mini-plant biological indexing will enable citrus clean stock and/or certification programs to be more productive while using fewer resources.