TABLE CONTENTS

AMF-induced Bioprotection against Migratory Plant-parasitic Nematodes:
Which Mechanisms are Responsible?
Elsen A., C. Vos, D. Gervacio, R. Swennen & D. De Waele
Department of Biosystems, Faculty of Bioscience Engineering, K.U. Leuven, Kasteelpark Arenberg 13, 3001
Leuven, Belgium
About 80% of all vascular plants on earth are colonized by symbiotic arbuscular mycorrhizal
fungi (AMF). Plants with a mycorrhized root system benefit from improved water and
nutrient uptake, which results in enhanced growth and survival. In addition AMF can reduce
the occurrence and impact of several soil pathogens and plant-parasitic nematodes. The
AMF-induced bioprotection has been reported for many nematode species in a wide range of
agricultural crops, but until now the mechanisms involved have seldomly been investigated
for AMF-nematode interactions. In the presented study the interaction was considered
between the migratory nematode Radopholus similis and the banana plant Musa cv. Grande
Naine, colonized by the AMF Glomus intraradices or G. mosseae. By using a split-root
experimental set-up in the first part of this study it was shown that not only a local
mechanism is responsible for the bioprotective effect, but also a systemic plant response. In
the second part, a step-by-step analysis based on the different nematode infection phases was
used to reveal the mechanisms responsible for the AMF-bioprotective effect. First, attraction
of the nematodes toward plant roots was studied in both in vitro and in vivo root exudate
experiments, for which exudates were collected from mycorrhized and non-mycorrhized
plants. In both experiments the non-mycorrhized exudates resulted in a neutral to attracted
nematode movement while nematodes were repelled by the mycorrhized exudates. Secondly,
in the penetration experiment a significantly lower R. similis penetration was observed in
mycorrhized banana roots. Considering the results of the root exudate experiments, a changed
root exudation in mycorrhized plants seems to be at least partially responsible. Finally, the
nematode reproduction was studied. After 8 weeks, the final population was significantly
higher in control plants, while the reproduction ratio was significantly higher in mycorrhized
plants.
Analysis of Expressed Sequence Tags (ESTs) of a Fungivorous Nematode
Aphelenchus avenae
Karim, N. & T. Kikuchi
Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan
The fungivorous ability and anhydrobiotic survival capability of A. avenae have potentially
increased its importance over the other free living soil nematodes. Despite the availability of
the genome sequence of Caenorhabditis elegans, the amount of genetic information available
for other free living nematodes remains very limited. To address this, we present an analysis
of over 3000 expressed sequence tangs (ESTs) from the A. avenae. A cDNA library was
constructed from mixed-stage A. avenae and used to generate ESTs. Clustering analysis
showed that 3075 ESTs could be grouped into 2174 clusters ranging in size from a single
EST (1835 cases) to 45 ESTs (1 cases). A great majority of the clusters showed similarity to
the genes of C. elegans and parasitic nematodes with known or predicted function and one
third of the expressed transcripts did not have significant similarity to any of the sequences in
current databases thus possibly representing novel genes. To the best of our knowledge, the
fungivorous nematode, A. avenae has no association or has only very rarely been found in
5 th International Congress of Nematology, 2008 257