VARIATION OF VIROID PROFILES IN INDIVIDUAL GRAPEVINE PLANTS - NOVEL GRAPEVINE YELLOW SPECKLE VIROID-1 MUTANTS SHOW ALTERATIONS OF HAIRPIN-I

This is the first report which gives a general survey about viroid var iant composition in a vineyard and within single plants. A German vine yard with 20-year-old grapevines (Vitis vinifera) of the cultivars 'Ba cchus' and 'Kerner' was analysed for viroid infections. Only grapevine yellow speckle viroid 1 (GYSVd1) and the grapevine isolate of hop stu nt viroid (HSVdg) were detected. Both viroids occur in several sequenc e variations. Eighteen novel GYSVd1 variants and two previously publis hed HSVdg main variants with six new minor variants were found. They w ere randomly spread in the vineyard. The distributions of GYSVd1 and H SVdg main variants and their accompanying subvariants differed even in neighbouring plants. We conclude that these individual viroid variant profiles are the result of 20 years of independent evolution, i.e. mu tation and selection, in each single plant. Four of the nine GYSVd1 ma in variants were mutated in the inverted repeats bordering the central conserved region. These base substitutions decreased the thermodynami c stability of a metastable structure called hairpin I.