Pratylenchus hippeastri n. sp. (Nematoda: Pratylenchidae) from amaryllis in Florida with notes on P. scribneri and P. hexincisus

A new root-lesion nematode Pratylenchus hippeastri n. sp. is described from amaryllis (Hippeastrum spp.) in Florida. The new species is characterised by a combination of the following morphological features of females: slender body, flat, plain and smooth face, head with two lip annuli, an incomplete third annulus, and with second lip annulus thicker than first, ellipsoidal stylet knobs, rectangular empty spermatheca with large round cavity, and conoid tail with bluntly pointed terminus usually showing a ventral constriction, or subhemispherical and smooth. The ranges of morphometric characters of P. hippeastri n. sp. overlap with those of P. scribneri and P. hexincisus. These three species also share some morphological and biological features such as two lip annuli, an empty spermatheca and similar lateral fields, but differ in the morphology of head patterns (smooth face in P. hippeastri n. sp. vs divided face in the others) and tail termini (hemispherical and subhemispherical in P. scribneri and subdigitate in P. hexincisus vs bluntly pointed in P. hippeastri n. sp.). A reference population of P. scribneri from Ohio and one of P. hexincisus from Tennessee were obtained during the course of unsuccessful attempts to recover P. scribneri at the type locale in Tennessee. The D3 rDNA sequences of the reference populations matched GenBank sequences for these two species. Small morphological differences between the P. scribneri population from Ohio and the P. scribneri lectotype occurred in the shape of stylet knobs (ellipsoidal vs round) and spermatheca (round with a central cavity vs oblong) and also in the length of the pharyngeal overlap (longer in the reference population). These morphological differences cast doubt about the identity of the lectotype, which may be P. hexincisus. New morphological details were obtained for P. hexincisus from Tennessee, which included a divided face, an almost rectangular empty spermatheca with a central cavity and subdigitate tail termini. Based on our phylogenetic inferences from DNA sequences P. hippeastri n. sp. is more closely related to P. zeae and a Florida population of P. loosi than to P. scribneri or P. hexincisus. © 2007 Koninklijke Brill NV.