TABLE CONTENTS

Population Distribution of Plant-Parasitic Nematodes of musa spp in
Peninsular Malaysia and Molecular Characterisation of Nematode Species
Rahman, S.A. (1), S.N. Md Zain (2) & Z. Mohamed (1)
(1) Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science,
University of Malaya, 50603 Kuala Lumpur, Malaysia; (2) Institute of Biological Sciences Faculty of Science,
University of Malaya, 50603 Kuala Lumpur, Malaysia.
Nematode infestation on bananas has been identified as the key contributing factor to
increased crop losses worldwide. Different plant-parasitic nematode species exhibit different
pathogenicity levels towards the hosts. Thus, knowledge of genetic diversity of the parasite is
crucial for the development of effective resistance breeding programme for the hosts. As
indistinguishable morphological variations were observed in nematode species, molecularbased
identification method poses as an attractive alternative to the conventional
identification procedures.
Nematode rDNA is comprised of multiple repeats of three ribosomal genes namely 18S, 5.8S,
28S and interspersed with internal transcribed spacer (ITS) regions. The highly conserved
nature of nematode rDNA genes enables the design of universal primers to amplify
orthologous ITS fragments from all nematode taxa. It was reported that copies of these spacer
regions are similar in a single individual but distinct amongst different nematode species.
Therefore, by using molecular approach, ITS regions from individual nematodes can be
analysed
This study aims to investigate intraspecific and interspecific genetic variations demonstrated
by the nematode isolates, thus, exploring the genetic diversity of the parasites. PCR was
performed by using two sets of universal rDNA primers for comparison of the ITS regions of
five nematode species isolated namely Radopholus similis, Meloidogyne incognita,
Helicotylenchus dihystera, Helicotylenchus multicinctus and Hoplolaimus spp. Isolated
amplified products were subjected to cloning and sequencing.
Initial results suggested that the size of amplified products could indicate the nematode
species from which the DNA was obtained. Heterogeneity within individual was detected in
R. similis, M. incognita, H. dihystera and H. multicinctus. ITS regions of all species showed
high homogeneity level which ranges from 83.2% to 98% with the exception of ITS 2 regions
amplified from M. incognita. In addition, interspecific heterogeneity was found in
Helicotylenchus genus. These findings are significant for future development of speciesspecific
primers or other DNA-based assays that could further ease nematode identification
process.
5 th International Congress of Nematology, 2008 67