C Time
Resume:
Journal of Invertebrate Pathology **, *** *** (***1)
doi:10.1006/jipa.2001.5029, available online at http://www.idealibrary.com on
Developmental Temperature Effects on Five Geographic Isolates
of the Entomopathogenic Nematode Steinernema feltiae
(Nematoda: Steinernematidae)
Selcuk Hazir,*, S. Patricia Stock,* Harry K. Kaya,* Albrecht M. Koppenhofer, and Nevin Keskin
*Department of Nematology, University of California, One Shields Avenue, Davis, California 95616-8668; Department of Biology,
Faculty of Science, University of Hacettepe, 06532, Beytepe, Ankara, Turkey; and Department of Entomology,
Rutgers University, New Brunswick, New Jersey 08901
E-mail: abpp1e@r.postjobfree.com
Received September 11, 2000; accepted March 1, 2001; published online June 6, 2001
larvae and dog-food agar medium were used, respec-
The development of ve geographic isolates of Stein- tively, for in vivo and in vitro culture of the Sinop
ernema feltiae at 5, 8, 10, 15, 20, 25, and 28 C in wax isolate. Infective juvenile body length showed the
moth, Galleria mellonella, larvae was examined. The same trends, with the longest being at 8 C and de-
isolates were from Mediterranean (Sinop from Tur- creasing in length from 15 to 23 C. The data suggest
key, SN from France, and Monterey from California), that quality of food for the nematode and temperature
(that is, developmental time) in uence the body length
subtropical (Rafaela from Argentina), and tropical
of the infective juvenile. 2001 Academic Press
(MG-14 from Hawaii) regions. All isolates caused 100%
Key Words: Insect-pathogenic nematode; Steinerne-
mortality of wax moth larvae and developed and pro-
matidae; Steinernema; size variation.
duced progeny between 8 and 25 C. At 28 C, mortality
was 100%, but no progeny was observed. The highest
infective juvenile production was observed at 15 C for
all isolates. In general, the tropical isolate, MG-14, had INTRODUCTION
the lowest production of infective juveniles. The time
of emergence of the infective juveniles from the host Entomopathogenic nematodes in the family Stein-
cadaver showed some differences among isolates, with ernematidae, currently represented by 25 species in
the Sinop isolate having the earliest emergence time the genus Steinernema and 1 species in the genus
from cadavers at 15 C (10 days) and 20 C (8 days). At
Neosteinernema, are obligate, lethal parasites of in-
25 C, the infective juveniles of the Sinop, SN, and
sects (Burnell and Stock, 2000). Steinernematids are
Rafaela isolates emerged from the cadavers from 5 to 7
mutualistically associated with enteric bacterial spe-
days. Time of host death by all isolates showed no
cies (Xenorhabdus spp.) that occur in the intestine of
differences at 8, 10, 15, 20, and 28 C. At 25 C for all
the infective juvenile nematode stage (Boemare et al.,
isolates (except the MG-14), shorter times to host
1996; Forst and Nealson, 1996), and each nematode
death were observed. Host death occurred at 12 days
species is associated with a speci c bacterial species.
at 8 C, 9 to 11 days at 10 C, 4 to 5 days at 15 C, 3 days
The infective juvenile, which is the only free-living
at 20 C, and 2 days at 25 and 28 C. For penetration
stage, searches for a susceptible insect host, enters it
ef ciency, the Sinop, SN, and Rafaela isolates pene-
through natural openings, penetrates the hemocoel,
trated their hosts at 5, 8, and 10 C. Penetration of the
and releases the bacterial cells that kill the host within
infective juveniles was consistently high for all iso-
48 h (Kaya and Gaugler, 1993). The bacterial symbiont
lates at 15, 20, 25, and 28 C, but it was signi cantly
digests the host tissues, thereby providing suitable
lower for the MG-14 isolate at 15, 25, and 28 C. No
nutrient conditions for nematode growth and develop-
progeny production occurred at 28 C, but nematode
ment.
penetration did occur with the MG-14 isolate having
Entomopathogenic nematodes can be very effective
signi cantly lower penetration than the other isolates.
biological control agents against a number of insect
When nematodes were produced at 8, 15, and 23 C in
pests and possess several advantages over chemical
wax moth larvae, all isolates had infective juveniles
pesticides (Kaya and Gaugler, 1993). For example,
with longer body lengths at 8 C followed by 15 and
they can actively nd their hosts, can recycle in the soil
23 C. To further verify body length at the different
environment (Kaya and Gaugler, 1993), and are envi-
temperatures, beet armyworm, Spodoptera exigua,
243-****-****/01 $35.00
Copyright 2001 by Academic Press
All rights of reproduction in any form reserved.
244 HAZIR ET AL.
TABLE 1
Sources of Steinernema feltiae Isolates Used in This Study
Isolate Geographic origin Habitat Climatic region Insect host Source
a
SN Southern France Unknown Mediterranean Unknown G. O. Poinar
Rafaela Santa Fe, Argentina Alfalfa eld Subtropical Graphognathus leucoloma S. P. Stock
Unknown a
Monterey California, USA Grassland Mediterranean S. P. Stock
Unknown a
MG-14 Hawaii, USA Under tree Tropical A. Hara
Unknown a
Sinop Sinop, Turkey Grassland Mediterranean S. Hazir
a
Nematodes recovered with soil baiting technique.
ronmentally safe (Akhurst, 1990). Moreover, they have reared separately in wax moth larvae (Rainbow Meal-
a global distribution (reviewed by Hominick et al., worms, Compton, CA) (Kaya and Stock, 1997). After
1996), and many surveys have been conducted to iso- the wax moth larvae died, they were placed in White
late new strains and species for biological control pro- traps, and the infective juveniles were allowed to
grams or to determine their biodiversity (Akhurst and emerge and were collected every other day. The infec-
Bedding, 1986; Constant et al., 1998; Yoshida et al., tive juveniles were stored at 15 C.
1998; Stock et al., 1999). To verify that the isolates were the same species, we
A signi cant amount of research has been conducted conducted a cross-mating study. We used 24-well tis-
to elucidate the biology of these nematodes, including sue culture plates which were lined with a piece of
the systematics, ecology, and biological control poten- lter paper (1.5 cm diameter) in each well. One infec-
tial (Gaugler and Kaya, 1990; Kaya and Gaugler, 1993; tive juvenile from each of the two test isolates was
Burnell and Stock, 2000). Much of the research has placed in each well by use of a 10- l microdispenser.
focused on individual species or comparisons between Then, one wax moth larva (200 300 mg) was placed
and among species. Researchers are interested in in- into each well. This protocol was repeated for each
traspeci c variations that occur among different iso- nematode isolate. As a control, two infective juveniles
lates of the same species for determining variation in from the same population were placed together as de-
morphology (Poinar, 1992; Stock et al., 2000), genetics scribed above. Each dead wax moth larva was placed
(e.g., Gaugler et al., 1989), physiology (e.g., Jagdale on a White trap and the emergence of infective juvenile
and Gordon, 1997; Fitters et al., 1999; Solomon et al., progeny was used as an indicator that breeding be-
1999), infectivity (Grif n and Downes, 1991), and cli- tween isolates occurred.
matic adaptation (Solomon et al., 1999). Temperature
is one of the important factors affecting the infectivity, Infectivity and Developmental Studies
time of death, development, reproduction, and storage at Different Temperatures
of entomopathogenic nematodes (Grif n, 1993; Grewal
Tissue culture plates with 24 wells were lled with
et al., 1994; Finnegan et al., 1999; Koppenhofer and
0.5 g of pasteurized air-dried sandy loam soil to which
Kaya, 1999). In this paper, we report ndings on the
60 l of nematode inoculum containing 50 infective
effect of temperature on four of these parameters (in-
juveniles was added. Two plates per isolate per tem-
fectivity, time of death, development, and reproduc-
perature were placed in incubators set at 5, 8, 10, 15,
tion) in ve isolates of Steinernema feltiae using the
20, 25, 28, and 30 C. After 1 h acclimation, one wax
wax moth, Galleria mellonella, as a host. We also stud-
moth larva was added to each well. Whereas both sets
ied the effect of temperature on infective juvenile
of plates were used to determine the time of death of
length in these isolates and the effect of temperature in
the wax moth larvae, one set of plates was used for the
relation to food source on infective juvenile length in
infectivity study based on penetration ef ciency, and
one of these isolates.
the other set was used for the developmental study. In
addition, two control plates without nematodes (60 l
MATERIALS AND METHODS
of distilled water) were included in the study to verify
the health of the last instar wax moth larvae (Koppen-
Nematode Source and Culture
hofer and Kaya, 1999). The plates were placed into
Five isolates of S. feltiae from different geographical polyethylene bags to prevent desiccation. All ve S.
regions of the world were obtained and information feltiae isolates were included in this study and the
about their source, geographic location, and host are experiment was conducted twice.
detailed in Table 1. The isolates originated from Amer- To determine the time of death, each larva was
ica (Monterey and MG-14), Argentina (Rafaela), probed daily, and if the larva did not respond to the
France (SN), and Turkey (Sinop). Each isolate was probe, it was considered dead. At 5 C the living wax
245
TEMPERATURE EFFECTS ON FIVE S. feltiae ISOLATES
moth larvae were so sluggish that time of larval death exigua larvae (obtained from Agraquest, Davis, CA)
with the protocol described above for the wax moth
could not be determined adequately and death was
larvae. This experiment was done only once with 24 S.
assumed based on the characteristic color associated
exigua larvae.
with a S. feltiae infection.
To determine the effect of in vitro production, the
To determine the penetration ef ciency of the infec-
infective juveniles were grown on a dog-food medium.
tive juveniles, the wax moth larvae were checked daily
One-week-old infective juveniles were surface-steril-
for mortality. When a larva died, it was rinsed in
ized in 0.1% Hyamine 1622 solution (benzethonium
distilled water to remove the external nematodes.
chloride) (Sigma, St. Louis, MO) (Kaya and Stock,
Dead larvae from 5, 8, 10, or 15 C were placed at room
1997) for 30 min and rinsed three times in sterile
temperature (23 C) for 2 additional days, whereas lar-
water. About 250 infective juveniles in 100 l were
vae recovered at 20, 25, and 28 C were held for 1 day
placed in a 35-ml test tube containing 5 ml of sterilized
(modi ed after Koppenhofer and Kaya, 1999). No in-
dog-food agar medium and held at 23 C. When infec-
fection was observed at 30 C and this temperature was
tive juveniles were produced, they were harvested for
discontinued. After this time period, each cadaver was
the temperature studies. Three tubes were inoculated
dissected and digested with pepsin solution (Mauleon
each with ca. 250 infective juveniles and were main-
et al., 1993) and the number of penetrated (i.e., estab-
tained at 8, 15, or 23 C and checked every other day for
lished) nematodes was counted.
nematode development. When infective juveniles were
For the developmental study, 8 dead wax moth lar-
observed on the side of the tubes, they were harvested
vae from the group of 24 that were exposed to S. feltiae
by the adding of 15 ml of sterile water and the pouring
were selected to determine the time and number of
of the contents into a beaker. The nematodes were
infective juvenile emergence. These cadavers were
allowed to settle, and the supernatant was discarded.
placed individually on an emergence White trap which
More water was added and the process repeated until
consisted of a 35 10-mm petri dish lid lined with
the nematode suspension appeared clear. Infective ju-
lter paper, situated in a 100 15-mm petri dish
veniles were obtained by the adding of 0.1% sodium
containing sterilized distilled water (Koppenhofer and
hypochlorite (NaOCl) to the beaker for 15 min, which
Kaya, 1999). The traps were kept at the original incu-
killed the developing nematodes, leaving behind the
bation temperatures and checked daily. We recorded
infective juveniles (Kaya and Stock, 1997). The infec-
the rst day that infective juveniles were observed
tive juveniles from the tubes at each given temperature
emerging from the host. Once they entered the water,
were pooled and approximately 250 to 300 of them
they were collected at regular intervals until no more
were xed in TAF, and 25 infective juveniles from each
infective juveniles entered the water. The total number
temperature were measured as described previously.
of infective juveniles emerged was estimated by the
This experiment was repeated twice.
counting of subsamples at a magni cation of 50 .
Statistics
Temperature Effects on Infective Juvenile Length
Data on time of death, nematode penetration, repro-
A separate set of experiments with wax moth larvae
duction, and total body length of the infective juveniles
was conducted to determine the effect of temperature
were analyzed with analysis of variance (ANOVA), and
on the body length of emerging infective juveniles of
signi cant differences among means were separated by
the ve geographic isolates of S. feltiae. The infective
Tukey s test (SAS Institute, 1996).
juveniles of each isolate were allowed to infect wax
moth larvae at 8, 15, and 23 C as described above. Six
RESULTS
cadavers were used for progeny production and placed
individually on White traps. Three days after the in-
When each of the ve geographic populations of S.
fective juveniles emerged, they were collected from the
feltiae was crossed with each other, viable progenies
White trap; a pool of 40 50 infective juveniles/cadaver
were produced (data not shown). No infectivity of S.
was heat-killed at 60 C and stored in triethanolamine
feltiae was observed at 30 C. In general, the wax moth
formalin (TAF) solution (Kaya and Stock, 1997). From
larvae used as controls in the developmental studies at
this pooled sample, 25 infective juveniles were mea-
various temperatures appeared healthy.
sured with a Nikon Eclipse E600 microscope with
Scion Image software (1.62a version).
Infectivity and Developmental Studies
To determine whether infective juvenile body length
at Different Temperatures
was also in uenced by temperature (8, 15, or 23 C) if
reared on a different host or in vitro, we conducted the Time of death. Temperature had a signi cant effect
following experiments with one S. feltiae isolate (Si- on the time of host death by S. feltiae (Fig. 1A). All
nop). To determine the effect of a different host, infec- isolates elicited the fastest time of death at 25 and
tive juveniles were produced in last-instar Spodoptera 28 C and the slowest time of death at 8 C. The time
246 HAZIR ET AL.
FIG. 1. The effect of temperature on four different parameters on ve geographical isolates of Steinernema feltiae. (A) Time to death of
wax moth host. (B) Number of nematodes established in wax moth larvae. (C) Time of emergence of rst infective juvenile from host cadaver.
(D) Total number of infective juveniles (IJs) emerged per wax moth larva.
of death was not signi cantly different among the respond to probing even though they appeared to be
isolates at 8, 10, 15, 20, and 28 C ( P 0 .05). At alive.
25 C, time of death was signi cantly longer for MG-14
Penetration ef ciency. At 15 and 20 C, all S. feltiae
than for the other isolates ( F 1 4.64; df 4,211;
isolates penetrated in relatively high numbers ( 20) in
P 0 .001). We were unable to determine the time of
the wax moth larvae. At 15 C ( F 6 .1; df 2,121;
death at 5 C because the wax moth larvae did not
247
TEMPERATURE EFFECTS ON FIVE S. feltiae ISOLATES
TABLE 2
Mean Standard Error of Body Length of Five Isolates of Steinernema feltiae Infective Juveniles Reared
in Galleria mellonella Larvae at Different Temperatures
Temperature
( C) SN Rafaela Monterey MG-14 Sinop
8 1033 14A,a 990 15A,a 1008 11A,a 1002 14AB,a 939 10B,a
(803 1098) (885 1100) (795 1079) (853 1048) (901 1173)
15 916 20A,b 935 15A,a 964 13A,b 915 17A,a 928 19A,b
(716 1138) (774 1071) (795 1033) (764 1045) (689 1081)
23 843 23A,c 850 13A,b 870 14B,c 788 12A,a 903 13AB,c
(738 1016) (749 1001) (694 926) (798 1013) (601 1036)
Note. Measurements are in micrometers and the range is shown in parentheses. Means within the same row followed by the same capital
letter are not signi cantly different ( P 0 .05; Tukey s test). Means within the same column followed by the same lower case letter are not
signi cantly different ( P 0 .05; Tukey s test).
P 0 .001), however, the MG-14 isolate penetrated isolates. At 15 C ( F 3 .33; df 1,82; P 0 .01) and
and established at signi cantly lower numbers than 20 C ( F 1 .80; df 1,82; P 0 .136), there were
the Sinop and Rafaela isolates (Fig. 1B). At 5 C ( F signi cant differences only between the Sinop and the
1 0.2; df 3,115; P 0 .001), 8 C ( F 1 7.94; df MG-14 isolates, with the MG-14 isolate producing less
3,115; P 0 .001), and 10 C ( F 1 3.68; df 3,100; infective juveniles than the Sinop. However, signi -
P 0 .001), the MG-14 and Monterey isolates pene- cant differences were observed between the Sinop and
trated and established at signi cantly lower numbers SN and the Monterey and MG-14 isolates at 25 C ( F
than the Sinop, SN, and Rafaela isolates. At 25 C ( F 8 .43; df 1,58; P 0 .001). No signi cant differ-
4 .93; df 4,136; P 0 .001), the MG-14 isolate had ences were observed among any of the isolates at 10 C
signi cantly lower establishment than the other iso- (P 0 .10).
lates. At 28 C ( F 1 3.64; df 4,159; P 0 .0001),
the MG-14 isolate had signi cantly lower penetration Temperature Effects on the Length
(16.5 infective juveniles/host) than the other isolates of Infective Juveniles
(range 22.9 34.8 infective juveniles/host). No signi -
Our results indicated that the developmental tem-
cant differences in penetration ef ciency were ob-
peratures affected the length of emerging infective ju-
served at 20 C ( P 0 .30) (Fig. 1B).
veniles (Table 2). For all isolates, the longest infective
Emergence time. All isolates showed the fastest
juveniles were recovered at the lowest temperature
emergence time ( rst emergence from the cadaver) at
(8 C) and the shortest were at the highest temperature
20 and 25 C and the slowest emergence time at 8 C; no
(23 C).
infective juveniles emerged at 5 and 28 C (Fig. 1C). No
The Sinop ( F 2 4.4; df 2,72; P 0 .0001), SN
signi cant differences among isolates were observed at
(F 2 4.2; df 2,72; P 0 .0001), and Monterey
10 C ( F 0 .58; df 4,22; P 0 .68). However, at
(F 5 4.8; df 2,72; P 0 .0001) isolates exhibited
8 C ( F 4 .9; df 1,24; P 0 .005), there was a
signi cant differences in the total body length of the
signi cant difference between the MG-14 and SN iso-
infective juveniles among the three temperatures. The
lates. At 20 C ( F 4 .6, df 3,75; P 0 .002),
Rafaela isolate ( F 3 0.04; df 1,72; P 0 .0001)
signi cant differences were observed among the Sinop,
exhibited signi cant differences only between 8 and
Rafaela, Monterey, and MG-14 isolates. Additionally,
23 C and 15 and 23 C, respectively. In the MG-14, the
signi cant differences were observed between one
longest infective juveniles were observed at 8 C and
group (MG-14 and Monterey) and the other group (Si-
the shortest at 23 C, but the means did not differ signif-
nop, Rafaela, and SN) at 25 C ( F 1 6.1; df 1,72;
icantly (F 1.72; df 1,72; P 0.185) (Table 2).
P 0 .001). At 15 C ( F 3 0.2; df 4,60; P
In the in vivo method with S. exigua, maximum
0 .001), MG-14 emergence started signi cantly later
infective juvenile length was obtained from cadavers
than the other isolates. Differences also occurred
kept at 8 C and the minimum infective juvenile length
among the Monterey, Rafaela, and Sinop isolates.
was obtained from nematodes at 23 C. However,
length of the Sinop infective juveniles differed signi -
Number of emerged infective juveniles. All isolates
cantly ( F 9 .72; df 1,72; P 0 .0002) between 8
showed the lowest number of emerged infective juve-
and 15 C and 8 and 23 C, but not between 15 and 23 C
niles at 8 C and the highest number of emerged infec-
(Table 3).
tive juveniles at 15 C (Fig. 1D). Signi cantly more
In the in vitro method with dog-food agar, infective
Monterey infective juveniles emerged at 8 C ( F
1 2.3; df 4,15; P 0 .001) than the four other juvenile length of the Sinop isolate differed signi -
248 HAZIR ET AL.
TABLE 3 1997). Even the tropical isolate (MG-14) did compara-
tively well at low temperatures.
Mean Standard Error of Body Length of the Sinop In-
fective Juveniles Reared from Spodoptera exigua Larvae and Other researchers have shown that different isolates
Dog-Food Agar at Different Temperatures of the same species of entomopathogenic nematodes
have differential responses to various factors. Gaugler
Temperature
et al. (1989) screened 22 isolates of S. carpocapsae from
( C) Spodoptera exigua Dog-food agar
four different continents for host- nding ability and
8 903 18A,a 923 19A,a
ultraviolet light (UV) tolerances. They found differ-
(755 1005) (781 1000)
ences among the 22 isolates and selected 10 of them for
15 851 20A,b 906 16A,a
further analysis. Host- nding ability of the infective
(651 999) (689 1003)
23 814 6A,b 815 14A,b juveniles of 3 isolates was signi cantly better than that
(765 897) (701 941)
of the other isolates, but there was a clear gradation
from very good to poor host- nding ability. However,
Note. Measurements are in micrometers and the range is shown in
the 10 isolates showed a narrow UV tolerance, indicat-
parentheses. Means within the same row followed by the same
capital letter are not signi cantly different ( P 0 .05; Tukey s test). ing that genetic variability for this trait was low. So-
Means within the same column followed by the same lower case
lomon et al. (1999) demonstrated that a S. feltiae iso-
letter are not signi cantly different ( P 0 .05; Tukey s test).
late from Israel s Negev Desert was better adapted for
desiccation tolerance than an isolate from Germany. In
temperature studies, Wright (1992) showed that two
cantly only between 8 and 23 C and 15 and 23 C ( F isolates of S. feltiae from New Zealand had differences
1 0.6; df 2,72; P 0 .0001). Although the infective in the number of infective juveniles produced, and the
juveniles were longer at 8 than at 15 C, no signi cant time for reproduction and emergence was less for one
difference was observed between these two tempera- isolate than another isolate. Grif n and Downes
tures ( P 0 .05). There was no signi cant difference (1991), working with four different Heterorhabditis iso-
in body length at each temperature ( P 0 .31) be-
lates, showed that some isolates were better than oth-
tween S. exigua-reared and in vitro-reared infective
ers in infecting their host at low temperatures. Our
juveniles (Table 3).
data con rm Wright s (1992) study that differences in
progeny production, time of death of host, time of emer-
DISCUSSION
gence, and number of penetrated infective juveniles in
a host can vary among S. feltiae isolates.
Our study demonstrated that similarities and differ-
Temperature can also affect the length of the infec-
ences occur among isolates of the same entomopatho-
tive juvenile progeny that are being produced. Schi-
genic nematodes in their response to temperature.
rocki and Hague (1997) demonstrated that infective
Temperature had a direct effect on the time of death,
juveniles of S. feltiae that were produced for four re-
penetration rate, emergence time of infective juveniles,
productive cycles at 10 C were longer (966 m) than
and number of emerging infective juveniles of the ve
those that were produced continuously at 22 C (896
isolates of S. feltiae. However, differences among the
m). When S. feltiae was reared at 10 C and then
ve isolates in some of the parameters indicated that
reared for one cycle at 22 C, the resulting infective
geographic isolation resulted in adaptation of the iso-
juveniles measured an average of 892 m. Our study
late to the given region.
con rmed that S. feltiae infective juveniles from ve
The Sinop, SN, and Monterey isolates are from Med-
geographical isolates were longer when reared at lower
iterranean areas, Rafaela is from a subtropical area,
temperature (8 C) than at higher temperature (23 C).
and the MG-14 isolate is from a tropical area. At 28 C,
Schirocki and Hague (1997) speculated that the longer
none of the isolates produced progeny, and the nema-
development time at the lower temperatures results in
todes developed to the rst generation adults but were
more nutrient uptake and larger infective juveniles.
unable to proceed to the next generation. At the other
We also observed the same temperature effect on
extreme, the MG-14 and the Monterey isolates had
infective juvenile body length when the Sinop isolate
very low numbers of penetrated nematodes in the host
was reared on another insect host (S. exigua) or on
at 5, 8, and 10 C compared with the other isolates. At
dog-food medium. Although we could not statistically
25 C, the MG-14 took signi cantly longer to kill its
compare the body length of the infective juveniles from
host than the other isolates. In general, the Monterey
S. exigua and dog-food agar medium with those reared
and MG-14 isolates were similar in many of the param-
on the wax moth larvae, our data strongly indicate that
eters that were measured, and the Sinop, SN, and
infective juveniles tend to be longer when reared in
Rafaela isolates were likewise similar in many param-
wax moth larvae than in S. exigua and on dog-food
eters. All isolates had the most progeny production at
agar. It appears that the host species or arti cial me-
15 C. Clearly, S. feltiae is adapted to lower tempera-
tures (Grewal et al., 1994, 1996; Schirocki and Hague, dium can in uence the body length of the infective
249
TEMPERATURE EFFECTS ON FIVE S. feltiae ISOLATES
cides (M. Laird, L. A. Lacey, and E. W. Davidson, Eds.), pp.
juveniles. S. exigua larvae probably have a lower nu-
233 240. CRC Press, Boca Raton, FL.
tritional quality than wax moth larvae.
Akhurst, R. J., and Bedding, R. A. 1986. Natural occurrence of insect
Nguyen and Smart (1995) observed that when stein-
pathogenic nematodes (Steinernematidae and Heterorhabditidae)
ernematids and heterorhabditids were reared in wax
in soil in Australia. J. Aust. Entomol. Soc. 25, 241 244.
moth larvae at 25 C, there was a negative linear rela-
Boemare, N. E., Laumond, C., and Mauleon, H. 1996. The ento-
tionship between the body length of the infective juve- mopathogenic nematode bacterium complex: Biology, life cycle
niles and the time of harvest. With respect to an un- and vertebrate safety. Biocontr. Sci. Technol. 6, 333 3435.
identi ed strain of S. feltiae, Nguyen and Smart (1995) Burnell, A. M., and Stock, S. P. 2000. Heterorhabditis, Steinernema
showed that on the 1st day of harvest the infective and their bacterial symbionts Lethal pathogens of insects. Nema-
juveniles averaged 914 m but by the 15th day of tology 2, 31 42.
harvest they averaged 794 m. The shortest body Constant, P., Marchay, L., Fischer-LeSaux, M., Briand-Panoma, S.,
and Mauleon, H. 1998. Natural occurrence of entomopathogenic
length of the infective juveniles (632 m) was obtained
nematodes (Rhabditida: Steinernematidae and Heterorhabditi-
from arti cial medium (brain heart infusion, corn oil,
dae) in Guadeloupe islands. Fundam. Appl. Nematol. 21, 667 672.
cholesterol, agar, and water). In our study, the body
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length of the infective juveniles of the Sinop isolate 1999. Effect of salt and temperature stresses on survival and
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Smart (1995). Other factors affecting body size of the Gouge, D. H., and Hague, N. G. M. 1995. The development of Stein-
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Our results show that there are variations among
of entomopathogenic nematodes: Niche breadth for infection, es-
the ve geographical isolates of S. feltiae. The Sinop,
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Rafaela, Monterey, and MG-14 isolates have been cul-
Grewal, P. S., Gaugler, R., and Wang, Y. 1996. Enhanced cold toler-
tured under laboratory conditions for only a few gen- ance of the entomopathogenic nematode Steinernema feltiae
erations, whereas the SN isolate has been under labo- through genetic selection. Ann. Appl. Biol. 129, 335 341.
ratory cultivation for a much longer time. We expected Grif n, C. T. 1993. Temperature responses of entomopathogenic
to see greater variation in the tropical isolate than in nematodes for the success of biological control programs. In Nem-
those that were from the Mediterranean climatic re- atodes and the Biological Control of Insect Pests (R. Bedding, R.
Akhurst, and H. Kaya, Eds.), pp. 101 111. CSIRO Publications,
gions. The tropical isolate, MG-14, had some differ-
East Melbourne, Australia.
ences compared with those from the Mediterranean
Grif n, C. T., and Downes, M. J. 1991. Low temperature activity in
climatic region, with the Monterey isolate being inter-
Heterorhabditis sp. (Nematoda: Heterorhabditidae). Nematologica
mediate. Our data suggest that these isolates have 37, 83 91.
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ACKNOWLEDGMENTS Technol. 6, 317 331.
Jagdale, G. B., and Gordon, R. 1997. Effect of propagation tempera-
This study was supported in part through a Scienti c and Tech- tures on temperature tolerances of entomopathogenic nematodes.
nical Research Council of Turkey grant to S. Hazir. We thank S. Fundam. Appl. Nematol. 211, 177 183.
Nadler for use of microscope and video image software for conducting
Kaya, H. K., and Gaugler, R. 1993. Entomopathogenic nematodes.
the morphometric observations and the Genetics Resources Conser-
Annu. Rev. Entomol. 38, 181 206.
vation Program for their continued support for maintenance of the
Kaya, H. K., and Stock, S. P. 1997. Techniques in insect nematology.
entomopathogenic nematode collection.
In Manual of Techniques in Insect Pathology (L. Lacey, Ed.), pp.
281 324. Academic Press, San Diego.
Koppenhofer, A. M., and Kaya, H. K. 1999. Ecological characteriza-
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