Morphological and molecular characterisation of populations of Longidorus longicaudatus Siddiqi, 1962 and L. americanus Handoo, Carta, Skantar, Ye, Robbins, Subbotin, Fraedrich & Cram, 2005 from Florida, USA

Abstract

Summary Two populations of needle nematode, Longidorus longicaudatus Siddiqi, 1962, are described from Quercus hemisphaerica, Q. nigra and Q. virginiana from north Florida, USA. These populations are characterised morphologically by females having a body shorter than 3800 μm, a rounded or slightly flattened lip region, an amphidial fovea pouch-like often with two symmetrical lobes, an odontostyle 99-110 μm long, a conoid tail ending in a bluntly pointed terminus, ranging values of ratio c′ greater than 2, and males very rare. The polytomous code for these populations is A34, B23, C2, D23, E2, F12, G12, H6, I12, J1, K6. Although the morphology and morphometrics of these two populations fit the original description of Longidorus longicaudatus, Florida specimens have greater diameters of lip region, mid and anal body than those of the five type specimens used for the description of this species. The Florida L. longicaudatus is similar to L. paralongicaudatus, but differs from the paratypes of this species in having smaller and greater values of ratios c (53.8 (43.8-64.5) vs 79.2 (61.9-103.5)) and c′ (2.4 (2.1-2.9) vs 1.8 (1.5-2.0)), respectively, and longer tail (60 (53-67) vs 46 (36-53) μm). Molecular characterisation of one of the two Florida L. longicaudatus populations was made based on the D2-D3 of 28S rRNA, ITS1 rRNA and COI gene sequences. The results of the ITS1 rRNA gene sequence analysis indicated that it is genetically different from L. paralongicaudatus. A few specimens of a needle nematode associated with L. longicaudatus were identified morphologically and molecularly as the pine needle nematode, L. americanus. This detection is a new record of the occurrence of the pine needle nematode in Florida.