|Hughes Watson, Pamela|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2004
Publication Date: 4/6/2004
Citation: Hughes Watson, P.L., Scorza, R. 2004. Evaluation of long term disease resistance in mature field-grown plum pox virus resistant plum trees (Prunus domestica L.). American Pytopathological Society Potomac Division 2004 Meeting, Book of Abstracts. p. 22. Interpretive Summary:
Technical Abstract: Plum pox virus (PPV), a member of the genus Potyvirus, is one of the most destructive viral diseases of Prunus species. PPV causes fruit symptoms such as light green or yellows rings, deeply engraved rings and spots, and brown gum-like deposits in the flesh of plum (Prunus domestica L.) rendering the fruit unmarketable and resulting in economic losses for producers. Traditional plant breeding has produced few varieties of Prunus that are highly resistant to PPV. Through the use of genetic transformation, PPV resistant plum trees containing the PPV coat protein (CP) have been produced. PPV-CP transgenic plum clone C5 was found to be highly resistant to PPV. C5 plants displayed characteristics typical of post-transcriptional gene silencing (PTGS), including a high level of transcription in the nucleus, low levels of transgene mRNA in the cytoplasm, and methylation of the silenced PPV-CP transgene (Scorza et al., 2001). DNA methylation has consistently been associated with PTGS in many species. The aim of the current study was to evaluate the level of methylation of the PPV-CP transgene in leaf tissue from 6-8 year old field-grown C5 trees. PPV-CP transgene DNA C5 trees was stable and consistently more highly methylated at three time points (April, July, and October) during the three growing seasons in comparison to other PPV-CP transgenic plums that were neither silenced nor PPV resistant. Methylation levels in C5 started out relatively low in April, increased to their highest levels in July, and then decreased again in October. Even though methylation levels decreased in October, these levels were at least twice those measured in April. This study demonstrates both the long term stability and seasonal fluctuation of PTGS-related transgene methylation in a perennial fruit tree.