Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: April 16, 2008
Publication Date: July 21, 2008
Citation: Scorza, R., Hily, J., Callahan, A.M., Damsteegt, V.D., Ravelonandro, M. 2008. The development of 'HoneySweet' - a transgenic Plum pox virus (PPV) resistant plum and the application of intron-hairpin (ihp) RNA technology for PPV resistance in stone fruits. HortScience. 4:1069. Technical Abstract: Genetic engineering (GE) has the potential to revolutionize fruit tree breeding and is an important addition to the fruit breeder's "toolbox". It is an approach that can specifically target genetic improvements and allow for the development of novel, useful traits. In spite of the potential utility of GE for fruit tree improvement, the technology has not, to date, been widely exploited in these species, and no GE temperate fruit species have been released. Plum pox virus (PPV) is a major pathogen of stone fruits that entered the U.S. in 1999 and is the subject of a quarantine and eradication program. We have developed a GE plum clone C5 (cv. HoneySweet) that is highly resistant to PPV through the mechanism of post-transcriptional gene silencing (PTGS), also termed RNA silencing. 'HoneySweet' is an example of GE that can be of significant benefit to growers and consumers, one that can also provide unique genetic material for use in conventional breeding programs. The development and testing, including long-term field test data from several coutries, and current regulatory status in the U.S. of 'HoneySweet' will be presented. Based on the success with 'HoneySweet', we used self-complementary PPV coat protein sequences separated by an intron to produce a "hairpin" RNA (ihpRNA) structure. The ihpRNA construct was used to elicit PTGS to confer resistance to PPV in transgenic Nicotiana benthamiana, where we confirmed the high capacity of ihpRNA constructs for inducing RNA silencing with more than 75% of transformants displaying PTGS. Utilizing ihpRNA technology on plum, we developed a number of GE lines that produced small interfering RNA which are diagnostic for RNA silencing. One plum line has been evaluated and is resistant to PPV demonstrating the direct application of ihpRNA technology for developing virus resistance in woody perennial species.