Grapevine yellows (GY) are diseases associated to phytoplasmas that occur in many grape growing areas worldwide and are of still increasing significance.

[1] Phytoplasmas are obligate cell wall-less bacterial pathogens (class Mollicutes), and rely on plants and homopterous phloem-sucking insects for biological dispersal.

[2] Almost identical symptoms of the GY syndrome are caused by different phytoplasmas and appear on leaves, shoots and clusters of grapevine.

Although no resistant cultivars of Vitis vinifera or rootstocks are known so far, the various grape varieties differ considerably as far as symptom severity is concerned.

[3] It ranges from fast decline and death in highly susceptible cultivars to tolerant rootstocks as symptomless carriers of the pathogen.