No abstract

Plum pox virus (PPV) is one of the most devastating diseases of Prunus species. Since few sources of resistance to PPV have been identified, transgene-based resistance offers a complementary approach to developing PPV-resistant stone fruit cultivars. C5, a transgenic clone of Prunus domestica L., containing the PPV coat protein (CP) gene, has been described as highly resistant to PPV in greenhouse tests, displaying characteristics typical of post-transcriptional gene silencing (PTGS). We show in this report that C5 trees exposed to natural aphid vectors in the field remained uninfected after 4 years while susceptible transgenic and untransformed trees developed severe symptoms within the first year. C5 trees inoculated by chip budding showed only very mild symptoms and PPV could be detected in these trees by IC-RT-PCR. The PPV-CP transgene in C5 was specifically hyper-methylated with no detectable expression. These results indicate both stability and efficiency of PTGS-based PPV resistance in plum under field conditions.

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.

Prehistory has produced evidence for two meaningful regularities in human evolution: tool making and the collection and use of ochre. Tools and tool making have been acknowledged as fossil indicators of human skill, mental capacities, and social and cultural development.

This paper concerns the development of an immunosensor for detection of Plum pox virus in plant extracts. The sensor was based on gold electrodes modified with: 1,6-hexanedithiol, gold nanoparticles, anti-PPV IgG polyclonal antibody and BSA. It was used for determination of the virus in extracts from plum (Prunus domestica) and tobacco (Nicotiana benthamiana) leaves. The proposed electrochemical impedance spectroscopy (EIS) immunosensor displayed a very good detection limit of 10 pg/mL and a wide dynamic range from 10 pg PPV/ mL to 200 pg/mL. The presence of extracts from plant materials has no influence on the immunosensors response. The immunosensor was capable of discriminating between samples from healthy plants and samples containing 0.01 % of extract from infected plant material. The conditions for immunosensor regeneration are also presented.