"FasTrack" Breeding to Produce New Plum Pox Virus Resistant Plum Germplasm and Cultivars

Tuesday, July 23, 2013: 12:15 PM
Springs Salon D/E (Desert Springs J.W Marriott Resort )
Ralph Scorza , USDA–ARS, Appalachian Fruit Research Station, Kearneysville, WV
Chris Dardick , USDA–ARS, Appalachian Fruit Research Station, Kearneysville, WV
Ann Callahan , Appalachian Fruit Research Center, USDA–ARS, Appalachian Fruit Research Station, Kearneysville
Chinnathambi Srinivasan , USDA–ARS, Appalachian Fruit Research Station, Kearneysville
Doug Raines , USDA–ARS, Appalachian Fruit Research Station, Kearneysville, WV
Ted M. DeJong , University of California, Davis, CA
Sarah Castro , Plant Sciences Department, University of California, Davis, CA
Plum pox virus (PPV) is one of the most destructive diseases of plum and other stone fruits.  The virus entered the United States in 1999 and currently appears to have been eradicated.  In Canada after a decade-long unsuccessful eradication effort, PPV is under a monitoring and management program.  Over the past 20 years an intensive international research project has focused on the development of genetically engineered (GE) resistance to PPV.  This program has resulted in the development of a GE plum variety ‘HoneySweet’ that has been tested for 15 years in the United States and the European Union. It is highly resistant to PPV and it has received full regulatory approval in the United States.  Resistance to PPV in  ‘HoneySweet’ is RNAi-based and represents a new source of PPV resistance for breeders and for growers.  ‘HoneySweet’ can be used in breeding programs to develop additional resistant varieties and/or rootstocks.  To rapidly incorporate PPV resistance into new plum varieties requires novel approaches to breeding that can reduce or eliminate inherent tree breeding limitations, such as: long juvenility periods; the need for extensive and costly breeding plots; and yearly limitations on flowering and fruiting related to seasonal dormancy.  To address these limitations we have developed a system to dramatically shorten the breeding cycle of plum. "FasTrack" breeding overcomes the juvenility and environmental limitations of flowering and fruiting by incorporating into plums the Poplar FT (PtFT) gene that induces plum trees to flower early and continually.  We have reduced the plum generation cycle from 3–6 years to less than one year.   The "FasTrack" system allows for the rapid incorporation of the PPV resistance transgene into new hybrids.  Hybrids containing the resistance-inducing transgene can be selected immediately following seed germination and an accelerated backcross program is being used to move PPV resistance from 'HoneySweet' into germplasm adapted to different growing areas such as California and the northern United States.   Adapted PPV resistant cultivars that result from this preemptive breeding program will be available to growers in the event that PPV should reappear in the United States.
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