Bursaphelenchus juglandis n. sp. (Nematoda: Aphelenchoididae), an associate of walnut twig beetle, Pityophthorus juglandis, the vector of thousand cankers disease
2020
Ryss, Alexander Y. | Parker, Corwin | Álvarez-Ortega, Sergio | Nadler, Steven A. | Subbotin, Sergei A.
Bursaphelenchus juglandis n. sp. was isolated from the walnut twig beetle, Pityophthorus juglandis, and walnut trees, Juglans spp. with symptoms of thousand cankers disease, in California, USA. Based on analysis of three rRNA genes and morphological features (three lines in lateral field, small arched vulval flap in female, broad spicule with two lines along blade and small cucullus, digitate dorsally bent condylus, male tail pattern of five papilliform papillae and one pair of glandpapillae (P5), and curved conical female tail), the new species belongs to the Abietinus group within Bursaphelenchus. It differs from similar species of this group by the presence of a cephalic disc with lateral labial sensilla at the disc border, and in having thick spicules with the capitulum surface almost parallel to a virtual direct line extending from the spicule end. An emended diagnosis, tabular polytomous identification key and compendium of species with the lists of their vectors, plant hosts, and distribution are provided for the Abietinus group. The diagnostics of the propagative developmental stages is given, including sex differences; the transmission dauer stage was identified as the third stage and its description given with sexual differences. A molecular phylogeny of Bursaphelenchus is provided based on partial 18S rRNA, ITS rRNA and the D2-D3 expansion fragments of 28S rRNA gene sequences. A PCR with a species-specific primer was developed for detection of B. juglandis n. sp.
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