Morphological and Molecular Characterization of the Colomerus Vitis Erineum Strain (Trombidiformes: Eriophyidae) from Grapevine Erinea and Buds

The grapevine erineum mite strain (GEM) of Colomerus vitis (Pagenstecher) has spread throughout the main viticultural areas worldwide and was recently demonstrated to be a vector of Grapevine pinot gris virus (GPGV) and Grapevine inner necrosis virus (GINV). Its females mainly overwinter under the outer bud scales as winter morphs (deutogynes). Goals of this study were to characterize the morphology of protogynes (spring-summer morphs) and deutogynes (winter morphs), to confirm their genetic similarity, and to establish the seasonal period of the deutogyne occurrence. Buds or leaves from a single vineyard (cv. Luisa), Bari area, Apulia, Italy, infested with GEM were sampled 6 × from December 2015 to January 2017. Sixty-six traits commonly used for taxonomic identification were analysed on females. The length of the tibial setae l' on leg I and the tarsal setae ft' on leg II, as well as the number of smooth dorsal semiannuli differed significantly between protogynes and deutogynes, and were easier to detect than other significantly distinctive traits. ITS1 was investigated in individuals collected from buds and erinea, and the sequences confirmed that these two morphs have identical ITS1 fragments. The 1-year study demonstrated the simultaneous presence of protogynes and deutogynes in July and September 2016, whereas only protogynes were found in April and May 2016, and only deutogynes in December 2015 and January 2017.