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Goldfinger and a few other cultivars. Studies have shown that different isolates may differ in
pathogenicity on different banana cultivars.
Cobon and Pattison (2003), conducted glasshouse trials using several cultivars of Musa spp.
(banana) and showed that different Australian isolates had varying levels of pathogenicity.
Therefore, we intend to investigate R. similis isolates using molecular analysis in an attempt
to identify genetic groupings that might reflect different levels of pathogenicity. Previous
phylogenetic studies will be supplemented with further work using the internal transcribed
spacer region (ITS) of the nuclear rRNA to determine evolutionary relationships of
haplotypes within R. similis. If pathogenicity is linked to known genotypes, knowledge of
which isolate occurs in a region might assist in the selection of resistant banana cultivars and
eventually reduce the need for nematicide applications.
Based on the preliminary results of the ITS sequences, it appears that R. similis is not native
to Australia. All Australian isolates sequenced (n=10; Queensland and northern New South
Wales) had an identical haplotype, which is nested within a cluster of haplotypes originating
mainly from Asia. For the pathogenicity test, the preliminary result on several cultivars of
banana shows that isolates from Pimpama are more aggressive than other isolates. We are
currently using Amplified Fragment Length Polymorphisms (AFLP) to assess whether there
is variation among isolates of R. similis from different regions.
Comparison of the 28S Gene D2/D3 Expansion Segments of Stem
Nematode (Ditylenchus dipsaci) and Potato Rot Nematode (Ditylenchus
destructor)
Douda, O. (1), M. Zouhar (2), J. Mazáková (2), M. Marek (2) & P. Ryšánek (2)
(1) Division of Plant Health, Crop Research Institute, Prague, Czech Republic; (2) Department of Plant
Protection, Czech University of Life Sciences, Prague, Czech Republic
The Stem Nematode (Ditylenchus dipsaci) is the major pest of many economically important
crops. Effective management of this pest is complicated by existence of populations with
different host preferences. Some populations are specialized on a few host plant species;
others are able to attack plant species from all sorts of families. Another problem is the ability
of Ditylenchus dipsaci to survive on infested plant debris for several years. The relative and
morphologically similar species Ditylenchus destructor is much less dangerous pest. The aim
of this work was to characterize variable 2D and 3D segments of the 28S gene of the
Ditylenchus dipsaci and Ditylenchus destructor nematodes and to assess differences between
sequences of the both species. After isolation the DNA was amplified with the use of
universal primers derived from the genome of Caenorhabditis elegans. Fragment of the
length of approximately 784bp and 779bp respectively was obtained in this manner; this
fragment was used for ligation into pTZ57R/T plasmid and transformation of competent cells
of Escherichia coli Dh5α. Plasmids were selected, isolated and cloned fragment sequenced.
The comparison of Ditylenchus dipsaci and Ditylenchus destructor populations revealed
extensive level of variability; the overall value of alignment score was only 78. Comparison
with NCBI database using BLAST algorithm revealed high sequence similarity of
Ditylenchus dipsaci D2/D3 segments with corresponding segments of Subanguina radicicola
nematode. The research was supported by the Ministry of Agriculture of the Czech Republic;
project numbers Mze-0002700603 and MSM 6046070901.
5 th International Congress of Nematology, 2008 189