Sorosphaera viticola, Life cycle and Distribution

The overall objective of the project is to reconnoitre the life cycle, the ecology, and the distribution of the newly- discovered grapevine-plasmodiophorid Sorosphaera viticola. The main project aims are: (i) To find unknown cytological stages of the life cycle of S. viticola. (ii) To determine the parasites host range within the genus Vitis and the identification of potential alternative host plants. (iii) To specify the geographical distribution and possible eco-climatic preferences of S. viticola. Sorosphaera viticola it the only known plasmodiphorid plant-parasite infecting woody plants and permantent crops. Hence, the question whether or not it its life cycle differs from other plasmodiophorid plant-parasites should be answered. Within the applied project, optimized DNA extraction and PCR methods for the detection of S. viticola in plant material will be used to identify the missing stages of the plasmodiophorid life cycle (zoosoporangia) in grapevines. Some plasmodiophorids develop zoosporangia in alternative host plants. These alternative hosts can play a decisive role in the parasites propagation and persistence; thus the question if there are intermediate host plants in the vineyards should be answered. Preferred entrance portals of the parasite into the root system of the host plant will be designated by screening the total root system of infected grapevines. Many different rootstock varieties are used all over the world; to determine the host range within the genus Vitis different "wild" Vitis sp. and rootstock varieties will be screened. Results of a previous screening of two infested vineyards, based on morphological methods, will be the foundation to determine the dissemination and the persistence of S. viticola in infested vineyards and grapevines. To ascertain if infections of grapevine with S. vitcola underlie a seasonal dynamics, samples will be taken four times a year. Until now S. viticola was found exclusively in cool-climate vine-growing regions and soils with a high water holding capacity. The optimized DNA extraction and PCR methods for the detection of S. viticola in plant material and soil samples will be used to find out whether S. viticola is a parasite with a cosmopolitan distribution or if it is restricted to specific eco-climatic conditions. The cornerstone of plant pathology is the identification of the organisms and/or the interactions of different organisms responsible for crop diseases. Without basic knowledge about pathogens or their vectors, diseases can neither be understood nor controlled. The data about life cycle, distribution, eco-climatic preferences and abundance of S. viticola will lead to a better understanding of its role as grapevine parasite. In the long run, these data will provide a basis for a better understanding of other soilborn pathogens in viticulture.