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ANTAGONISTS OF ROOT-LESION NEMATODE IN VERTOSOLS FROM THE
NORTHERN GRAIN-GROWING REGION
Y. Li A , N. Seymour A and G. Stirling B
A
AgriScience Queensland, DAFF, Leslie Research Facility, PO Box 2282, Toowoomba, Queensland 4350.
B
Biological Crop Protection, 3601 Moggill Road, Moggill, Queensland, 4070
Email: jady.li@daff.qld.gov.au
ABSTRACT. Surveys of grain-growing soils in north-eastern Australia aimed to identify natural enemies that may have
been capable of attacking root-lesion nematode (Pratylenchus thornei). The endospore-forming bacterial parasite Pasteuria
was found in 25 of 97 paddocks surveyed, but less than 6% of the P. thornei generally had spores attached. Since little is
known about parasitism of P. thornei by Pasteuria, further research is being undertaken to determine whether adults and
juveniles are killed by the parasite, whether levels of spore attachment and infection will increase with time, and whether the
parasite will eventually provide some control of the nematode. Eight taxa of omnivorous and predatory nematodes were
found in 48 soil samples from 24 paddocks, with the nematodes usually more frequent at 0-15 than 15-30 cm. Four species of
nematophagous fungi (Arthrobotrys conoides, Stylopage sp., Monacrosporium thaumasium and A. oligospora) were
recovered in 52 soil samples from 26 paddocks. They were detected in 42, 19, 8 and 4% of samples, respectively.
INTRODUCTION
Root-lesion nematode (Pratylenchus thornei) is a major
pathogen of wheat in the northern grain-growing region of
Australia. Previous research has shown that antagonists of
nematodes, such as predatory nematodes and nematode
trapping fungi are present in the clay soils of this region (1).
The aim of the surveys described here was to obtain more
information on the distribution of these organisms. A second
objective was to determine whether the endospore-forming
bacterium Pasteuria, an obligate parasite of P. thornei, was
present in northern grain-growing soils.
range in population densities between paddocks indicates
that the presence of these nematodes could be affected by
soil type, cropping history and other management practices
such as tillage.
×200
MATERIALS AND METHODS
From February to June 2011, soils at 0-30 cm were collected
from 97 paddocks in 30 districts of Queensland and northern
New South Wales. In each sample, about 50 P. thornei were
checked for the presence of Pasteuria. Soil samples from 24
paddocks at 2 depths (0-15 and 15-30 cm) were used for the
predatory nematode investigation. Soil (150 g) was placed
on trays for 2 days and nematodes were recovered on a 20
um sieve. Omnivorous and predatory nematodes were
identified to genus, family or order level. For the survey of
nematophagous fungi, 4 replicate samples from 26 paddocks
and 2 depths (0-15 and 15-30 cm) were processed using the
sprinkle plate method. Soil (1g) was plated onto ¼-strength
corn meal agar and about 5000 bacterial-feeding rhabditid
nematodes were added to each plate. Plates were checked
for the presence of fungi after 9, 16 and 24 days.
RESULTS AND DISCUSSION
We found P. thornei infested with spores of Pasteuria in 25
of 97 paddocks (Fig 1). At the sites where Pasteuria was
present, usually less than 6% of the P. thornei had spores
attached. Although the frequency of Pasteuria occurrence
was low, this discovery may be important, as species of
Pasteuria are capable of suppressing populations of other
plant-parasitic nematodes. Little is known about parasitism
of P. thornei by Pasteuria, as the parasite has only been
recorded from Germany and Turkey (2). Thus, further
research is needed to determine whether levels of spore
attachment and infection will increase with time, and
whether the parasite will eventually provide some control of
the nematode.
Eight taxa of omnivorous and predatory nematodes were
found in 48 soil samples and their population densities
varied with site and depth. The maximum number of
nematodes found at any site and depth, and their proportion
as a percentage of the total nematode population is given in
×100 ×400
Figure 1. P. thornei with spores of Pasteuria spp. attached.
Table 1. Omnivorous and predatory nematodes in northern
grain-growing soils.
Nematodes/kg dry
Taxa
soil
Proportion (%)
0-15 cm 15-30 cm 0-15 cm 15-30 cm
Aporcelaimellus 452 166 4 5
Belondiridae 643 391 3 3
Discolaimidae 89 0 0.002 0
Eudorylaimus 443 439 13 8
Other Dorylaimida 387 608 2 4
Mononchida 403 190 2 1
Tripyla 96 105 1 1
Total predators 1602 1238 13 13
Only four species of nematophagous fungi were
recovered: Arthrobotrys conoides, Stylopage sp.,
Monacrosporium thaumasium and A. oligospora, and they
were detected in 42, 19, 8 and 4% of samples, respectively.
Molecular detection techniques are being considered as a
means of confirming whether these predatory fungi are
relatively uncommon in northern grain-growing soils.
ACKNOWLEDGEMENTS
We thank GRDC for financial support and the Soil
Microbiology group at LRF for their technical assistance.
REFERENCES
1. Li, Y.J. and Stirling G.R. (2010). Proceedings, Sixth
Table 1. Discolaimidae only appeared at 0-15 cm. Other Australasian Soilborne Diseases Symposium. p 64.
genera were found at both 0-15 and 15-30 cm, but were 2. Chen, Z.X. and Dickson D.W. (2010). Journal of
usually more frequent at 0-15 cm. The highest density of Nematology. 30: 313-340.
omnivores/predators was 1602 nematodes/kg dry soil. The
7th Australasian Soilborne Diseases Symposium 28