Articles
PROGRESS IN THE BIOLOGICAL AND MOLECULAR STUDIES OF SOME IMPORTANT VIRUSES OF SOLANACEAE IN THE MEDITERRANEAN
Since 1988, outbreaks of CMV strains either supporting or not a satellite RNA (CARNA5) have recurred in solanaceous vegetables grown in the Mediterranean area.
Tomato crops were the most affected displaying a variety of disease patterns.
Evolution of CMV strains and associated satellites in the field was analysed mainly in Spain and Italy so that several CARNA5 variants were characterised at the molecular and biological level.
In Italy, a CARNA5 variant with necrogenic phenotype in tomato was recently isolated from naturally infected tobacco plants giving a clue to the possible sources of necrogenic types.
TSWV is widespread and since 1989 its recurrent epidemics became a limiting factor for the cultivation of many ornamental and vegetable species also in France, Italy and Soain.
The most important natural vector of TSWV is the thrips Frankliniella noccidentalis, now endemic in several areas.
Its presence, together with long distance movement of infected plants or propagating material can be considered the major single factor of the increasing incidence of TSWV-induced diseases in Mediterranean countries.
TSWV is currently identified by ELISA and by digoxigenin-labelled riboprobes.
Dominant genes for resistance in tomato have been identified and breeding for commercial types is in an advanced stage, whereas the results of preliminary breeding in pepper are under evaluation.
Most of the research on TYLCV isolates has addressed: i) comparative sequencing of genomic DNA, ii) study of trnasmission mechanism and identification of natural reservoirs; iii) control of viral epidemics.
Comparison of the deduced amino acid sequences of the putative ORFs of some Mediterranean TYLCV isolates showed high degree of similarity of the viral coat protein between isolates of the same cluster, strongly suggesting a similar mode of insect transmission.
This was demonstrated for an Italian isolate which persists in the vector for a shorter time (8 days) than the Israeli isolates (25 to 35 days). Much effort was also devoted to development of diagnostic methods (serological and molecular) to detect the virus in plants and vectors and to genetics and biotechnological approaches to control viral epidemics.