Spatial and temporal stolbur population structure in a cv. Chardonnay vineyard according to vmp1 gene characterization



Bois noir is a grapevine disease caused by the stolbur phytoplasma. It is widespread in all European and Mediterranean viticultural areas, and it can induce severe damage to the quality and quantity of production. The recent disease recrudescence has encouraged studies on the use of molecular markers to assess the genetic diversity of stolbur strains. The aim of this study was to evaluate the presence of Bois noir symptoms and to monitor the spatial genetic structure of the stolbur population according to vmp1 genotypes, through 2011 and 2012 in a cv. Chardonnay vineyard. In both years, there were increased vines with symptoms from July to September. The analysis of dispersal indices showed that the spatial distribution was uniform in the vineyard. However, the two-dimensional contour maps show that Bois noir severity was higher in plants located on the borders than in the central parts of the vineyard. Stolbur population was composed of two prevalent vmp genotypes (V14, V12) across both years, along with other minor haplotypes (V3, V4, V9, V11, V15, V18, in 2011; V3, V18 in 2012). The data indicate that the vmp1 gene is an efficient marker to study the population structure of stolbur phytoplasma, to track the movement of the pathogen, and to identify the inoculum source, which will all serve in the planning of control strategies.