Field Trials of Plum Clones Transformed with the Plum pox virus Coat Protein (PPV-CP) Gene

Abstract

Transgenic clones C2, C3, C4, C5, C6, and PT-6, of plum (Prunus domestica L.) transformed with the coat protein (CP) gene of Plum pox virus (PPV), PT-23 transformed with marker genes only, and nontransgenic B70146 were evaluated for sharka resistance under high infection pressure in field trials in Poland and Spain. These sites differed in climatic conditions and virus isolates. Transgenic clone C5 showed high resistance to PPV at 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 nontransgenic 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 a few mild symptoms on single, isolated shoots, even up to 8 years post inoculation. These results clearly indicate the long-term nature and high level of resistance to PPV obtained through genetically engineered resistance.

Biotech/GM crops in horticulture: plum cv. HoneySweet resistant to Plum pox virus

“…This is in agreement with the results obtained in France and Romania (Ravelonandro et al 1997(Ravelonandro et al , 2002, and in Spain and Poland (Malinowski et al 2006). Original results were obtained when graft inoculated trees were exposed to a very high infection pressure with IB being allowed to reach the size of 20-30% of the supporting HoneySweet tree (Figure 2).…”

“…Sharka disease is the most devastating disease of plum and is responsible for the reduction or loss of the plum production in many areas of Europe ). In the past 22 years of research by an international team of public sector scientists, a GM plum highly resistant to PPV was developed and thoroughly tested in the greenhouse and field, in the USA and Europe -the Czech Republic, France, Poland, Romania, and Spain for the resistance to PPV and for environmental safety (Scorza et al 1994;Ravelonandro et al 1997Ravelonandro et al , 2000Ravelonandro et al , 2002Hily et al 2004Hily et al , 2007Polák et al 2005Polák et al , 2008aMalinowski et al 2006;Capote et al 2007Capote et al , 2008Zagrai et al 2008aZagrai et al ,b, 2010). An original trial of a high and permanent infection pressure of PPV-Rec alone and in combinations with Prune dwarf virus (PDV) and Apple chlorotic leafspot virus (ACLSV) was initiated in the Czech Republic (Polák et al 2008a,b).…”

"HoneySweet" Plum—A Valuable Genetically Engineered Fruit-Tree Cultivar

“…HoneySweet) [6]. "HoneySweet" plum has proven to be highly resistant to PPV [7] and this high level of resistance has remained stable in European field tests for over 15 years under high PPV infection pressure [8]. Resistance in "HoneySweet" is based on gene silencing or RNA interference (RNAi) which is a natural virus defense system in plants [9].…”

Genetic Transformation Strategies in Fruit Crops

“…Obtained by transformation of ´Bluebyrd´ explants, C5 was derived from transformation events using A. tumefaciens strain C58/Z707 containing a binary plasmid with the coat protein (CP) PPV gene plus the 3' non-translated region of the viral genome (EMBL Accession No X16415, Teycheney et al, 1989). The high degree of resistance observed has been stable in more than 10 years of evaluations in greenhouses and in the field (Hily et al, 2004;Malinowski et al, 2006;Polák et al;. In C5, the clone has exhibited resistance associated to RNA interference (RNAi), i.e.…”