Major Outbreaks in the Nineteenth Century Shaped Grape Phylloxera Contemporary Genetic Structure in Europe.

Grape phylloxera is native to North America, where Vitis spp. acquired different mechanisms of resistance to leaf and root attack. Its appearance in European vineyards at the beginning of the 1860s, where the phylloxera-susceptible grapevine species V. vinifera L. is majorly cultivated, caused the devastation of a great number of vineyards, generating a deep crisis in the European wine production and trade industries. However, the origin and genetic structure of this pest across European vineyards still remain controversial and uncertain. Herein, we analysed the genetic structure of 1173 grape phylloxera individuals collected from 100 locations across eight European countries. Structure and phylogenetic analyses show that contemporary grape phylloxera populations in Europe are the result of at least two independent introductions from the native range that mirrors the historical records that also suggest two major outbreaks in Europe. The comparative analysis with samples from the native range trace back one of these two genetic groups to plants imported from the North East coast of North America, where the American species V. riparia and V. labrusca dominate. This study clarifies the level of genetic diversity of grape phylloxera in Europe and provides relevant information to resolve previous controversy about its origin.

Oxygen consumption-based evaluation of fungal activity.

A novel oxygen-based microplate assay for studying fungal activity is described. Fungal activity results in a change of oxygen concentration in CVC-96 plates and thus produces a signal that enables continuous monitoring of fungal activity. In this study the oxygen consumption was different for three tested fungi, Fusarium oxysporum f. sp. lycopersici, Verticillium dahliae and Trichoderma longibrachiatum. The assay described is a highly sensitive and reliable method for monitoring fungal activity. This assay does not interfere with fungal development and there is no need to kill the cells to take a measurement. This test would be useful for studying reactions that consume oxygen so possible applications of this test could be physiological studies, testing of fungicidal or fungistatic compounds, and studying enzyme reactions. The system provides a valuable insight into the kinetics of fungal activity and is suitable to test other systems.