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Sean Kelly and Ian Riley

Abstract

Large population densities (more than 100 000 per g dry weight of roots) of Radopholus nativus apparently caused economic damage to wheat near Wyalkatchem, Western Australia. Plants in large areas of poor growth were colonised by R. nativus, whereas in areas of better growth Pratylenchus neglectus occurred at lower population densities. The boundary between the areas was distinct. In the same year (1998), a further nine wheat samples were found to be infested with R. nativus through examination of 300 diagnostic samples submitted by Western Australian growers. Mixed Radopholus/Pratylenchus populations occurred in six of those samples. Populations of R. nativus were widely dispersed throughout the cropping areas of the State. It is concluded that R. nativus has the potential under certain conditions and/or crop rotations to reach high population density and cause economic loss.

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Kerrie Davies, Zeng Qi Zhao, Brett Alexander and Ian Riley

Abstract

A new genus and species of anguinid nematode, Litylenchus coprosma gen. n., sp. n., was recovered from leaves of Coprosma repens A. Rich. from an amenity planting in Wellington, New Zealand. The genus is characterised by having slender males and slender or semi-obese females, pharynx with a weak non-muscular median bulb, a terminal bulb containing the pharyngeal glands, female with a single gonad having a quadricolumella and post-uterine sac; male with arcuate spicules and the bursa arising 1-2 anal body diam. anterior to the cloacal aperture and extending nearly to the tail tip, and does not induce galls, only foliar chlorosis. The species is characterised by having a short, robust stylet with conus forming ca 40% of stylet length and three well developed rounded knobs, secretory/excretory pore opening posterior to the nerve ring, terminal bulb abutting the intestine, and tail tip of variable form. Molecular phylogeny of near full length small subunit, D2/D3 expansion segments of the large subunit and internal transcribed spacer rRNA genes support the description of L. coprosma gen. n., sp. n. as a new genus and species.

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Sergei Subbotin, Antoinette Swart, Louwrens Tiedt and Ian Riley

Abstract

Anguina woodi sp. n. was found in galls on dune grass, Ehrharta villosa var. villosa, on Milnerton Beach, South Africa. Mature galls varied in colour from purplish to brown and formed elongated to round elevations on the stems, leaf sheaths and, occasionally, the leaf blades. The adult females of Anguina woodi sp. n. are 1.6-2.7 mm long and coiled into a circle or spiral. Adult males were 1.4-2.1 mm long, straight or slightly curved ventrad or dorsad. Second-stage juveniles (J2) were more or less straight with a prominent mucro on the tail. A few larger juveniles, probably J3 and J4, with developing gonads were also found. Morphological, morphometric and molecular analyses showed that Anguina woodi sp. n. is closely related to A. australis Steiner, 1940 and, to a lesser extent, to A. microlaenae (Fawcett, 1938) Steiner, 1940. From A. australis it differs mainly in a slightly longer female stylet (9.5-15.5 vs 8.0-11.1 μm) and wider female head (8.6-11 vs 7.4 μm); a slightly longer male stylet (10.5-12.0 vs 10-11 μm) and longer spicule (33-36 vs 26.5-35.3 μm), and a longer tail (72-96 vs 49-68 μm) and slightly higher c-value (7.3-12 vs 6.1-8.1) in the J2. The mucro on the tail tip of the J2 of A. woodi sp. n. is also more prominent and, on average, longer than the mucro in A. australis (3.3 vs 1.5 μm). Anguina woodi sp. n. differs from A. microlaenae mainly in the appearance of the galls incited (roundish elevations attached to the substrate by a flattened base vs pedunculate galls attached to the substrate by a narrow base), a longer stylet in both females and males (8-9 μm long in females and males of A. microlaenae), body of male curved ventrad or dorsad in A. woodi sp. n. (dorsad in males of A. microlaenae) and female tail in A. woodi sp. n. tapering gradually to a sub-acute tip vs a prominent peg-like process in A. microlaenae. Phylogenetic analysis of the ITS1 sequences of 19 anguinid populations and species using maximum parsimony and maximum likelihood methods revealed that A. woodi sp. n. clustered with high bootstrap support with A. australis. The ITS1-5.8S-ITS2 fragment sequence differed between these species by 20 nucleotides (2.6%). The J2 of A. australis is herein described for the first time and is compared with the J2 of A. woodi sp. n. Phylogenetic relationships of A. woodi sp. n. with other anguinids parasitising grasses are presented.

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Zeng Qi Zhao, Kerrie A. Davies, Brett J.R. Alexander and Ian T. Riley

A new genus and species of anguinid nematode, Zeatylenchus pittosporum gen. n., sp. n., was recovered from leaves of Pittosporum tenuifolium from Hahei, Coromandel Region, North Island, New Zealand. The genus is characterised by having slender males and females, excretory pore opening near the lips and level with the knobs of the retracted stylet, pharynx with a weak non-muscular median bulb, pharyngeal glands overlapping the intestine, females with a single gonad with a quadricolumella and post-uterine sac; and males with slender arcuate spicules and the bursa arising <1 anal body diam. anterior to the cloacal aperture and extending ca 30% of distance to the tail tip. Its feeding does not induce galls, only foliar chlorosis. The species has particular characters, including a short, robust stylet with conus forming ca 40% of stylet length and small rounded compact knobs, and tail offset dorsally with a pointed tip. Molecular phylogeny of near full length small subunit, D2/D3 expansion segments of the large subunit and internal transcribed spacer rRNA genes support the description of Zeatylenchus pittosporum gen. n., sp. n. as a new genus and species.

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Zengqi Zhao, Kelley Thomas, Weimin Ye, Kerrie Davies, Dongmei Li, Robin Giblin-Davis and Ian Riley

Abstract

Six isolates of Australian Aphelenchoidoidea, viz., Laimaphelenchus preissii from native coniferous Callitris preissii trees, L. australis from the common pine plantation trees of Pinus radiata and P. pinaster and L. heidelbergi and two morphospecies of Aphelenchoides (H1 and K1) and Cryptaphelenchus sp. (K2) from diseased P. radiata trees, were studied using light microscopy, scanning electron microscopy and phylogenetic analyses of nearly full length sequences of SSU, D2/D3 expansion segments of LSU rDNA and a fragment of cytochrome oxidase subunit I (COI). Bayesian phylogenetic analyses of SSU, LSU and COI of the six nematode species revealed that none of these Australian aphelenchoidoids was inferred to be closely related to Bursaphelenchus. The selected isolates of Aphelenchoides and Laimaphelenchus used in this study were paraphyletic in all molecular analyses. Cryptaphelenchus sp. (K2) was inferred to be sister to Seinura with SSU sequences.