Grape phylloxera leaf-feeding populations in commercial vineyards – a new biotype ?

Abstract

Context and purpose of the study – Grape Phylloxera (Daktulosphaira vitifoliae Fitch) ordinarily has great difficulty establishing leaf galls on the European Grapevine (VitisviniferaL.). Yet populations of leaf-feeding Phylloxera are increasingly being observed throughout commercial vineyards world-wide. Effective plant protection strategies including quarantine actions are currently missing to fight, grape phylloxera populations in affected vineyards and combat linked negative effects on vines and yield. Contrary to the otherwise mandatory continuous infestation pressure from externally established populations (e.g. from populations developed on rootstock foliage or other interspecific hybrids, these leaf-feeding populations seem to establish themselves annually. The biotypes currently known (A-G) are differentiated based on their host-adapted performance on groups of Vitis plants (Vitis vinifera (E), American Vitis species (A), hybrids (ExA) and (AxA). A standardized protocol (double isolation chamber system) is employed to verify the hypothesis that these populations stem from a biotype, which is better adapted to create galls on V. vinifera leaves.

Material and methods –In the present study we monitored above- and belowground insect life table and host performance parameters of leaf-feeding grape Phylloxera strains collected from infested commercial vineyards. Standard phylloxera strains belonging to the biotypes A, B and C are used as anchor lineages for comparisons of phylloxera performance on the host plants: Teleki 5C, Riesling, Fercal and Marechal Foch. Three grape phylloxera strains from vineyards in Italy, Austria and Germany were monitored rating life table (insect based) and host performance (root- and leaf-gall based) parameters once per week for 40 days.

Results – our preliminary results clearly identified Grape Phylloxera lineages showing host-adapted performance attributed to Biotype G indicating superior performance on leaves of V. vin. cv. Riesling if compared with standard biotypes. These lineages maintained the traits over several asexual life cycles under controlled quarantine conditions and serve as experimental reference strains to further elucidate the mechanisms of these shifts in host performance. Studies on the impact of elevated temperatures to enhance fitness and population size of Biotype G Phylloxera are underway; as is research on the Phylloxera – grapevine interaction under climate change conditions, which may shed further light on the new phenomenon in commercial vineyards.
In conclusion biotype together with host plant genotype, environmental conditions, altered vineyard technology and management may affect the ecological network in vineyards leading enhanced susceptibility against leaf-feeding Phylloxera. Understanding and modeling of these factors is essential for the development of vineyard management strategies in phylloxerated wine areas.