TABLE CONTENTS

Observations on the Occurrence and Relationship of Nematodes in
Australian Conifers
Zhao, Z. (1), Y. Weimin (3,4,6), R.M. Giblin-Davis (4), D. Li (3), W.K. Thomas (6), K.A.
Davies (2) & I.T. Riley (2,7)
(1) Landcare Research, 231 Morrin Road, St Johns, Auckland 1072, New Zealand; (2) Plant and Food Science,
School of Agriculture Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, South Australia
5064, Australia; (3) North Carolina Department of Agriculture and Consumer Services, 4300 Reedy Creek
Road, Raleigh, NC27607, USA; (4) Fort Lauderdale Research and Education Centre, University of Florida,
Davie, FL 33314, USA; (5) CSIRO Molecular and Health Technologies, P.O. Box184, North Ryde, NSW 1670,
Australia; (6) Hubbard Centre for Genome Studies, University of New Hampshire, Durham, NH 03824, USA;
(7) Plant and Soil Health, SARDI, Plant Research Centre, Hartley Grove, Urrbrae, South Australia 5064,
Australia
Australia has large plantations of the exotic conifer Pinus radiata. This species is highly
susceptible to Bursaphelenchus xylophilus, which is not found in Australia. Potentially
pathogenic nematodes were isolated from several dead Pinus trees in Williamstown,
Heidelberg and other suburbs of Melbourne, Victoria in 2000-2002. A survey of the aboveground
nematode fauna of Pinus and native conifers in south-eastern Australia was made. A
total of 1140 samples from P. radiata, 50 from P. pinaster and 40 from Callitris preissii were
examined. No nematodes were found in wood or young shoots of conifers. By contrast,
nematodes were common in the bark samples.
Extracted nematodes were classified morphologically into five groups, including:
aphelenchida (plant, fungal and lichen feeders), rhabditids and areolaimids (bacterial
feeding), Macrolaimus spp. (saprophagus), tylenchids (plant feeding), and dorylaimids
(bacterial and algal feeders). Aphelenchids are the most common trophic group. About seven
different species of aphelenchoidoids were identified from all samples from the Pinus and
Callitris plantations and five species of aphelenchoidoids were identified from diseased trees.
Molecularly, six isolates of Australian Aphelenchoidoidea, viz., Laimaphelenchus preissii
from native coniferous C. preissii trees, L. australis from the common pine plantation trees of
P. 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.
5 th International Congress of Nematology, 2008 57