Xylella fastidiosa on grapevine in Mallorca, Baleares, ES
In Mallorca (Baleares, Spain), Pierce’s disease of grapevine caused by Xylella fastidiosa (EPPO A2 List) is considered to be established as the bacterium was detected in 17% of the 376 samples of grapevine (Vitis vinifera) tested in all vine-growing areas on the island (8 municipalities). It was evaluated that on average 7% of surveyed plants were infected and noted that the incidence was highly variable depending on sites (ranging from 0 to 99%). The economic impact on wine production was considered low. Vineyards managed under conventional viticulture had significantly lower levels of infection than organic vineyards. It is considered that weed control and soil tillage in spring may have a large impact on vector populations. In Mallorca, it was also observed that almond leaf scorch disease (caused by X. fastidiosa on Prunus dulcis) had a much higher incidence (approximately 78% of the 1 million almond trees on the island) and severity.
Inoculation trials were conducted and showed that X. fastidiosa could infect, to some degrees, 29 out of the 30 cultivars x rootstock combinations. It should be noted that 132 samples of grapevine collected from the other islands of Baleares (Formentera, Ibiza and Menorca) tested negative for X. fastidiosa.
Finally, a multilocus sequence typing analysis revealed that the Pierce’s disease epidemic in Mallorca is caused by the same clonal lineage (ST1) of X. fastidiosa subsp. fastidiosa affecting vineyards in the USA. The phylogenetic analysis supports the hypothesis that X. fastidiosa subsp. fastidiosa was originally introduced in Mallorca from California via infected almond scions around 1995 and that the bacterium was later transmitted to grapevine.
Sources
Moralejo E, Borràs D, Gomila M, Montesinos M, Adrover F, Juan A, Nieto A, Olmo D, Seguí G, Landa BB (2019) Insights into the epidemiology of Pierce's disease in vineyards of Mallorca, Spain. Plant Pathology 68(8), 1458-1471. DOI: https://doi.org/10.1111/ppa.13076