Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/4/2005
Publication Date: 4/11/2006
Citation: Malinowski, T., Cambra, M., Capote, N., Zawadzka, B., Gorris, M., Scorza, R., Ravelonandro, M. 2006. Field trials of plum clones transformed with the plum pox virus coat protein (ppv-cp) gene. Plant Disease. 90:1012-1018. Interpretive Summary: Genetic engineering offers the promise of disease control through non-chemical means. This technology could have important uses for tree fruits which are subject to a number of difficult to control disease problems including virus diseases. One of the most devastating virus diseases is plum pox virus which is an exotic disease organism that has recently invaded the U.S. We have developed plum pox virus resistant plum trees through genetic engineering. These had, until now, been determined to be resistant through artificial greenhouse tests. The true test of resistance can only be determined through long-term field studies. We report here a 7 to 8 year field test conducted in two European countries (Spain and Poland) that show conclusively that the genetically engineered plums are highly resistant to plum pox virus. This work shows the potential of genetic engineering for disease control in tree fruit crops.
Technical Abstract: Transgenic clones: C2, C3, C4, C5, C6 and PT-6, of plum (Prunus domesticaL.) transformed with the coat protein (CP) gene of Plum pox virus (PPV), PT-23 transformed with marker genes only, and non-transgenic B70146 were evaluated for sharka resistance under high infectioin pressure in field trials in Poland and in Spain. These sites differed in climatic conditions and virus isolates. Transgenic clone C5 showed high resistance to PPV in both sites. None of the C5 trees became naturally infected by aphids during seven (Spain) or eight (Poland) years of the test, although up to 100% of other plum trees (transgenic clones and non-transgenic control plants) grown in the same conditions showed disease symptoms and tested positively for PPV. Although highly resistant, C5 trees could be infected artificially by chip budding or via susceptible rootstock. Infected C5 trees showed only few mild symptoms on single, isolated shoots, even up to eight years post inoculation. These reults clearly indicate the long-term nature and high level of resistance to PPV obtained through genetically engineered resistance.