TABLE CONTENTS

Identification of Heteroprhabditis Species by SEM and Molecular
Techniques
Nguyen, K.B.
Entomology and Nematology Department, University of Florida, Gainesville, FL 32611-0620 USA
It is very difficult to use morphological characters or morphometrics to identify species in the
genus Heterorhabditis. Body length can only be used to divide all species into 2 groups. In
the first group, the infective juvenile (IJ) average body length is longer than 600 μm: H.
megidis, H. downesi, H. marelatus, H. zealandica. In the second group, IJ is shorter than 600
μm: H. amazonensis, H. baujardi, H. bacteriophora, H. floridensis, H. georgiana, H. indica,
H. mexicana, H. safricana, H. taysearae. Vulval pattern can be used to identify for a number
of species and gubernaculum structure can be used for species identification but it is difficult
to obtain. Molecular techniques using sequence analyses and phylogeny can be used to
identify all species of Heterorhabditis. Sequence length of ITS regions flanked by primers
18S and 26S, length of ITS1 and ITS2, distances between species, numbers of changes on
branches in a phylogenetic tree and the numbers of autapomorphies in the analysis of ITS
rDNA regions are reliable for species identification. Additionally, D2D3-LSU and ND4 can
be used for the same purpose. Phylogenetic trees using ITS and D2D3 group Heterorhabditis
species into 2 groups: the megidis group includes H. bacteriophora, H. downesi, H.
georgiana, H. marelatus, H. megidis, H. safricana, H. zealandica, while the indica group
includes H. amazonensis, H. baujardi, H. floridensis, H. indica, H. mexicana and H.
taysearae.
Distribution and Evalution of Entomophilic Nematodes (Heterorhabdus
and Steinernema) in Different Agroecosystems
Razia, M. & S. Sivaramakrishnan
Department of Biotechnology, Bharathidasan University, Tiruchirapppalli-620024, Tamilnadu, India
A survey of soil faunal nematode (Steinernematids and Heterorhabditids) was conducted in
different agro ecosystem of Tamilnadu, India. About 1000 soil samples were collected and
processed for nematodes distribution. In our study the nematode bionomics and distribution
was assessed with G. mellonella. The collective samples were positively 12% Heterorhabdus
spp. and 20% Steinernema spp. and identified as S. carpocapsae, S. glaseri and H.indica and
H. bacteriphora. In addition the collected strains were evaluated and screened for persistence
in different temperature (15 to 35°C) and pH ranges (5-8) and the infectivity was also
examined in the root grub (Holotrica serrata). Persistence was determined using baiting
nematode-inoculated soil and in the liquid medium in different temperature. Further
infectivity was assessed at different temperature against H. serrata using a filter-paper
bioassay and sand-well bioassay to determining nematode establishment. In our observation
infectivity and production rate was more in sand well bioassay method than filter paper both
Steinernema sp. and Heterorhabdus sp. and the optimum temperature for infection range 25 -
28°C. Hence, the distribution of epns acts as a biological control potential on insect pest and
diverse distribution in the agroecosystem due to geographical provision. Since the epns are
ubiquitous and vital for both ecofriendly and economically for sustainable management in an
agroecosystem.
5 th International Congress of Nematology, 2008 223