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Research Overview and Topics in 2005
36
The Department of Biological Safety includes the three research
groups of Plant Ecology, Entomology, and Microbiology, as well as
the Genetically Modified Or-ganism (GMO) Assessment Team, as
described below. The GMO Assessment Team was formed with the aim of
using recent advances in biotechnology and bioindustry for
environmental impact assessment of GMOs. The mission of the
Department as a whole is to assess the environmental impact of GMOs
as well as of alien inva-sive and introduced living organisms, and
to investigate the interaction of biodiversity and agriculture in
terms of biosafety and sustainable agriculture. The Department is
developing advanced methods to use in these assess-ments.
The major research domains of the Department are: 1) evaluation
of the influence of agricultural activities on agro-ecosystems and
biodiversity; 2) environmental im-pact assessment of introduced
natural enemies and alien invasive organisms; 3) identification of
biologically ac-tive chemicals and their effects on organisms in
agro-ecosystems; and 4) risk assessment of GMOs within
agro-ecosystems. Research is performed in col-laboration with other
research groups within and outside NIAES, and the approaches cover
a number of research fields, such as molecular, chemical,
population, and landscape ecology.
The research of the Plant Ecology Group is focused on vegetation
dynamics and conservation of vegetation, assessment of invasive and
introduced plant species in agro-ecosystems, and plant diversity in
relation to agri-cultural production. Current research topics are:
1) ef-fects of sulfonylurea herbicides on plant species, includ-ing
aquatic plants, in agro-ecosystems; 2) landscape ecological
approaches to the prediction of vegetation dynamics in relation to
farmland use; and 3) the search for allelochemicals and elucidation
of allelopathic mechanisms for maintaining agro-ecological
vegetation.
The Entomology Group focuses on the following three major
targets: 1) ecological risk assessment of alien insects such as
natural enemies of insect pests; 2) analy-sis of the population
dynamics of insect herbivores in response to the spatial
distribution patterns of plants; and 3) identification of
semiochemicals and analysis of the mechanisms of sex pheromone
resistance.
The Microbiology Group aims to characterize mi-crobial
communities and to develop technologies for effective management of
microbial resources in agro-ecosystems. Current research activities
are: 1) in-vestigation of microbial diversity and interactions in
the soil under different agro-ecosystems; 2) analysis of the
effects of environmental factors, including microbial secondary
metabolites, on the survival and diversity of
Department of Biological Safety
Photo Transplanting in a small paddy field that plays an
important role in bringing biodiversity to the campus at NIAES.
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37
microbes; and 3) determination of the taxonomy, biology, and
ecology of nematode communities.
The research objective of the GMO Assessment Team is to
investigate the effects of the release of GMOs on the environment.
The principal fields of interest are: 1) clarification of the
dispersal and transfer mechanisms of genes from GMOs to other
organisms; 2) assessment of the impact of Bacillus thuringiensis
(Bt) toxin in corn pollen on Lepidoptera; and 3) monitoring of
changes in the composition of weeds, insects, and soil
microorgan-isms caused by the cultivation of genetically modified
crops.
The major activities of the Department in FY 2005 were: 1)
publication of 10 main research results in the NIAES Major Research
Topics Annual (these results are described below as topics in the
introduction to the re-search groups and the team); 2) organization
of open seminars on “Invasive Alien Plant Species” at Tsukuba and
at Kurashiki in Okayama Prefecture, in December 2005 and March
2006, respectively; 3) implementation and coordination of research
projects on “Assurance of the Safe Use of Genetically Modified
Organisms” and “Risk Assessment and Control of Alien Plants”, and
par-ticipation in projects organized by such organizations as MAFF
and MEXT; and 4) attendance of departmental staff at many
international symposia and workshops.
Furthermore, in March 2005 Dr. K. Yamamura, a senior researcher
in the Population Ecology Unit, won an award from the Japanese
Society of Applied Entomology and Zoology for his research on the
development of sta-tistical methods for estimating population
parame-ters of insects (see Highlights).
1) Plant Ecology Group
The Plant Ecology Group consists of the Vegetation, Landscape,
and Chemical Ecology Units. These units individually carry out
research on the impact of agricul-ture on plant diversity; methods
for monitoring vegeta-tion changes in agro-ecosystems; and
interactions among agricultural organisms through biologically
active chemicals. The major results obtained in 2005 are de-scribed
below in research topics 1 and 2.
Topic 1: High susceptibilities of the aquatic fern Salvinia
natans to sulfonylurea herbicides
Since June 2005, fish, crustacean and green algae have been used
as test organisms to determine the regis-tration withholding limits
for pesticides in Japanese eco-logical impact assessments. However,
there is no evi-dence to confirm that green algae are suitable
representa-tives of aquatic plants in the testing of pesticides
toxici-ties. Therefore, we estimated the acute toxicities of a
major rice herbicide sulfonylurea in six aquatic vascular
plants, including four threatened species, and compared the
toxicities in these plants with those in the green alga
Pseudokirchneriella subcapitata (Ishihara 2005), which is a test
species used for the pesticide registration, and the blue-green
alga Merismopedia tenuissima (Ishihara 2005), which is a common
native species in Japan but is not used in official tests for
pesticide registration. We used hydroponic culture and soil culture
to examine the effect of a sulfonylurea herbicide
bensulfuron-methyl on the relative growth rate, and estimated the
50% effect concentration (EC50). Among the plants tested, the
threatened free-floating fern Salvinia natans (Photo 1) had the
highest susceptibility to bensulfuron-methyl, and the
susceptibility of this species was much higher than that of P.
subcapitata (Table 1), suggesting that the test species used for
pesticide registration is unable to detect the risk of
bensulfuron-methyl to the threatened S. natans. On the other hand,
M. tenuissima exhibited susceptibility comparable to that of S.
natans, suggesting that addition of this blue-green alga as a test
species would be useful for detecting the risks of
bensulfu-ron-methyl and would thus complement the ecological risk
assessment of pesticides under the present legal regulations.
Moreover, we conducted soil culture of S. natans to elucidate the
relative acute toxicities among three sulfonylureas,
bensulfuron-methyl, imazosulfuron and pyrazosulfuron-ethyl. The
acute toxicities of these three herbicides were comparable,
suggesting that they pose the same ecological risk to S. natans.
(H. Ikeda)
Photo 1 The threatened aquatic fern Salvinia
natans (All.). Plants were collected from lotus-cropping areas
around Lake Ka-sumigaura and raised outdoors in plastic boxes.
Naturally produced sporelings at the four- or five-leaf stage were
used for exposure experiments.
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Research Overview and Topics in 2005
38
Reference Ishihara, S. (2005) Concentrations of herbicides used
in
rice paddy fields in river water and impact on algal production.
Symposium Series 899, 112-123, American Chemistry Society.
Topic 2: Quantitative determination of cyanamide, improving
sensitivity, accuracy, robustness, speed, and operational
easiness
Cyanamide (H2NCN) is a multifunctional agro-chemical used, for
example, as a pesticide, herbicide, and fertilizer. Recent research
has revealed that cyanamide is a natural product biosynthesized in
some leguminous plants such as hairy vetch (Vicia villosa). We have
de-veloped a new method for the quantification of cyana-mide. In
this method, cyanamide is detected by gas chromatography – mass
spectrometry (GC–MS) instru-mentation equipped with a capillary
column for amines. Quantitative signals of (14N2)cyanamide (natural
cyana-mide), (15N2)cyanamide (internal standard for stable iso-tope
dilution method), and m- (trifluoromethyl) benzoni-trile (internal
standard for correcting errors in GC–MS analysis) are recorded as
peak areas on mass chroma-tograms at m/z 42 (A42), 44 (A44), and
171 (AIS), respec-tively (Fig. 1). The natural cyanamide content is
derived by multiplying the A42/A44 ratio by the amount of added
(15N2)cyanamide (stable isotope dilution – GC–MS method; SID–GC–MS
method). The limit of detection for the total cyanamide content by
the GC–MS analysis is around 1 ng. This method successfully gives a
reason-able value for the natural cyanamide content of hairy vetch.
The value is consistent with that obtained by a conventional method
in which cyanamide is derivatized to the photometrically active
compound 4-cyanimido-1, 2-naphthoquinone and analyzed by
reversed-phase
Table 1. Acute toxicities of bensulfuron-methyl (sulfonylurea
herbicide).
Hydroponic culture Soil culture (2002) Plant species
Taxonomic group
IUCN§ rank
Exposure time (d)
EC50 (µg L-1)
Exposure time (d)
EC50 (µg L-1)†
Azolla japonica Fern Ⅱ 12 2.0-5.8 20 6.8 Salvinia natans Fern Ⅱ
12 0.22-1.6 20 1.9 Marsilea quadrifolia Fern Ⅱ 10 28-47 20 9.7
Blyxa echinosperma Monocot Ⅱ 20 4000 Lemna minor Monocot Non 12
1.9-6.0 20 27 Spirodela polyrhiza Monocot Non 12 6.1-17 20 86
Pseudokirchneriella subcapitata ¶ Green alga Non 3 62 Merismopedia
tenuissima ¶ Blue-green alga Non 3 1.5
§The World Conservation Union, †50% effect concentration 1 day
after treatment, ¶ Ishihara (2005) Symposium Series 899, 112-123,
American Chemistry Society.
Fig. 1 Representative GC–MS chromatograms of a
sample solution prepared from a hairy vetch extract containing
natural cyanamide, 15(N2) cyanamide (internal standard for the
stable isotope dilution method), and m- (trifluoro-methyl)
benzonitrile (internal standard for correcting errors in the GC–MS
analysis): (A) signals recorded as the sum of mass chromatograms at
m/z 42, 43, 44, and 171; (B) mass chromatogram at m/z 42 for the
determination of (14N2) cyanamide; (C) mass chromatogram at m/z 44
for the de-termination of (15N2) cyanamide; (D) mass chromatogram
at m/z 171 for the determi-nation of m-(trifluoromethyl)
benzonitrile. The y-gain values of all chromatograms were adjusted
to the same value. The amount of 15(N2) cyanamide added was 88.2 mg
kg–1 fresh weight of hairy vetch.
TIC
m/z 44
m/z 171
(B)
(A)
(C)
8 9 10 11 12Retention time (min)
Inte
nsity m/z 42
(D)
Sum of mass chromatogram at m/z 42, 43, 44, and 171
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39
HPLC (CNQ-HPLC method); however, the SID–GC– MS method is much
more sensitive, accurate, and robust, as well as faster and
simpler, than the CNQ-HPLC method. (Hiradate et al., 2005). (S.
Hiradate, T. Kamo, E. Nakajima, K. Kato and Y. Fujii)
Reference Hiradate, S., T. Kamo, E. Nakajima, K. Kato, Y.
Fujii
(2005) Direct quantitative determination of cyana-mide by stable
isotope dilution gas chromatogra-phy–mass spectrometry. Journal of
Chromatography A, 1098: 138–143
2) Entomology Group The mission of the Entomology Group is to
prevent
the disturbance of agro-ecosystems by native and exotic insect
species and to assess the non-target effects of in-troduced
insects. In FY 2005, the three units of the Group studied three
major subjects covering eight prac-tical research subjects.
Furthermore, the Entomology Group conducted cooperative studies
with the Food Production Prediction Team, the GMO assessment team,
and the Plant Ecology Group.
The Introduced Insect Assessment Unit has been studying the
non-target effects of natural enemies intro-duced from overseas. As
case studies, we studied the potential for hybridization between
Torymus sinensis (the introduced parasitoid of the chestnut gall
wasp) and the indigenous species T. beneficus, and between the
intro-duced green lacewing Chrysoperla carnea and the in-digenous
species C. nipponensis. Interspecific offspring between T. sinensis
and T. beneficus could not be found in the field by using DNA
markers. Interspecific hy-bridization between C. carnea and C.
nipponensis oc-curred in the laboratory, but the rate was very low
(Topic 1). On the basis of the last 5 year studies, we have
pro-posed an environmental impact assessment methodology for
natural enemy introduction.
The Population Ecology Unit studied the effects of the spatial
distribution of a host plant, the common rag-weed Ambrosia
artemisiifolia, on the population dynam-ics of the ragweed beetle
Ophraella communa. The oc-currences of the ragweeds and beetles
were surveyed for 3 years in an area of about 400 ha surrounding
our Insti-tute. Population trend and spatial distribution analyses
showed that the beetle population fluctuated greatly from year to
year and that the ragweed patches were conta-giously distributed. A
spatially explicit model of the host plant – beetle system was
constructed, incorporating the spatial distribution of the host
patches, and a simulation was performed to estimate fluctuations in
the beetle population. The results suggested that the dispersal
rate
of the beetles and the distance between host patches are
important for stability of the beetle population.
The Insect Semiochemical Unit studied the influ-ence of a
communication disruptant, used to control the smaller tea tortrix
moth Adoxophyes honmai, on the egg-larval parasitoid Ascogaster
reticulatus. Under treatment with the communication disruptant,
adult eclo-sion, life span, exploratory behavior, mating behavior,
and egg-laying behavior in the egg–larval parasitoid were observed.
Average total egg-laying times in the treatment and control groups
were 1674 s and 2215 s, respectively, and these two values were
significantly different. Egg–larval parasitoids under treatment
more strongly avoided laying their eggs in eggs that were al-ready
parasitized than did the controls. However, the communication
disruptant was expected not to have an effect on the egg–larval
parasitoid, as the proportion of parasitized eggs (90.1%) under
treatment was almost the same as that of the controls (87.3%).
The insect Gene Bank Project has been run by the above mentioned
two units and the Insect Systematics Laboratory since 2000. The
purposes of this project are to collect and successfully rear
insect species or strains (e.g., for use as natural enemies or in
bioassays) and to supply these insects to laboratories requesting
them for research. In 2005, the indigenous Dichochrysa forma-sana
was added to the collection. Orius nagaii (Antho-coridae) was added
to the active collection. The total collection was 18 species as of
February 2006. The physiological and ecological characteristics of
about 31 items in the collection were evaluated.
Topic 1: Interspecific hybridization between intro-duced and
indigenous green lacewings (Neuroptera: Chrysopidae) at different
adult densities
Recently, there has been concern that the release of exotic
natural enemies might affect the biodiversity of native non-target
species. In Japan, the green lacewing, designated Chrysoperla
carnea has been imported from Germany since 2001 as a biopesticide.
Chrysoperla carnea has long been assumed to be a single widespread
morphological species with a Holarctic distribution. However,
evidence has been reported that it constitutes a complex of several
cryptic species that can be strictly divided into species only by
their courtship songs. The Japanese indigenous green lacewing had
also been cate-gorized as C. carnea, but it has now been revised to
C. nipponensis. Its courtship song is distinct from that of the
introduced green lacewing, whose song has the same pattern as the
true C. carnea. Because the two taxa are now in the same habitat,
there is, however, potential for either competitive displacement or
hybridization (and
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Research Overview and Topics in 2005
40
thus for loss of the potentially beneficial attributes of C.
nipponensis). Last year, I reported that the risk of com-petitive
displacement was low. This year, I present the results of
interspecific hybridization between C. carnea and C. nipponensis at
different adult densities in the laboratory.
Fertility as a function of cage capacity is shown in Figure 1.
Fertility was significantly reduced by expan-sion of cage capacity
in all four cross combinations. Fer-tility differed significantly
among conspecific or inter-specific crosses. In the interspecific
crosses, C. nippo-nensis females × C. carnea males showed lower
fertility than C. carnea females × C. nipponensis males in cages of
all sizes. On the other hand, no significant sex-related
differences were found in conspecific crosses of either C. carnea
or C. nipponensis. The hybridization ratio showed a similar pattern
if adult density was reduced. The results of this study suggest
that the potential hy-bridization ratios of interspecific crosses
are much lower than those of conspecific crosses at all the tested
adult population densities. This suggests that mechanisms are
present that cause reproductive isolation between the two
species.
In Japan, C. carnea is recommended for use only in greenhouses.
The release of from 10 up to about 40 lar-vae per 1 m2 of
greenhouse floor area is recommended in the explanatory note
supplied by Kagetaro®. If all the released C. carnea larvae at the
maximum density (40 individuals/m2) emerged in a standard
greenhouse (5.4 m
× 10.0 m × 3.5 m high), the adult density would be 1.143 × 10–5
individuals/m3. This density is considerably lower than that in the
largest cage in our experiment (two indi-viduals per 10 851 cm3,
corresponding to 184.31 indi-viduals/m3). Therefore, even if the
indigenous C. nippo-nensis were released at the same density as C.
carnea in the greenhouse, the frequency of interspecific
hybridiza-tion would be very low. There have been no field reports
of the establishment of C. carnea, or of natural hybrids being
produced between C. carnea and C. nipponensis in Japan. However, we
need to monitor the establishment of C. carnea and any unexpected
non-target effects in the wild. (A. Mochizuki)
Topic 2: Factors affecting the flight activity of the ragweed
beetle Ophraella communa, an exotic insect in Japan
The ragweed beetle Ophraella communa (Coleop-tera:
Chrysomelidae), which was originally distributed in North America,
was recently found in Japan (Takizawa et al., 1999) and Taiwan
(Wang and Chiang, 1998) in 1996 and in Korea in 2000 (Kwon et al.,
2000). In Japan, this exotic insect has rapidly expanded its
distribution since the first discovery and has been found in all
pre-fectures except Hokkaido and Okinawa. This fact sug-gests that
the beetle has a large potential for dispersal and flight.
To investigate the factors affecting the flight activi-ties of
the beetle, we measured its flight time with a flight measuring
system (flight mills) under several con-ditions in the laboratory.
The beetles exhibited low flight activity at the age of 1 to 3 days
post-eclosion. After 4 days their flight activity increased and
then remained high. The beetles reduced their flight activity at
night, although they flew both in the daytime and at night. Flight
activity was lower in adults reared under a 12:12 (L:D)-h
photoperiod, which induced a reproductive dia-pause, than in those
reared under a 16:8-h photoperiod. This photoperiodic response
could explain the seasonal changes in flight activity: the fourth
overwintering gen-eration of adults displayed the lowest activity.
During these experiments, we found a large variation in flight time
among beetle individuals (Fig. 2). We performed artificial
selection on the beetles for several generations on the basis of
their flight times. Bidirectional selection shifted the flight
times in opposite directions and estab-lished two beetle lines,
fliers and non-fliers. This result shows that there is a genetic
variation in the flight activ-ity of this beetle and that fliers
may contribute to the observed rapid expansion of this
distribution. (K. Ta-naka)
Fig. 1 Fertility (%) as a function of cage capacity.
Open circles, percentage of conspecific crosses of C. carnea;
solid circles, percentage of conspecific crosses of C. nipponensis;
open squares, percentage of crosses of female C. carnea × male C.
nipponensis; solid squares, percentage of crosses of female C.
nipponen-sis × male C. carnea
100
0
20
40
80
110 245 916 1,832 10,851Cage capacity (ml)
Fert
ility
(%)
60
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41
3) Microbiology Group The Microbiology Group aims to
characterize mi-
crobial communities in agro-ecosystems and develop technologies
for the effective management of microbi-ological resources. The
group consists of three research units, Microbial Ecology,
Microbial Genetics and Physi-ology, and Nematology and Soil
Zoology.
The work is conducted on the following research themes: 1)
investigation of the effects of soil microor-ganisms on the
population dynamics of sclerotium- forming fungi: 2) investigation
of the effects of secon-dary metabolites from microorganisms and
plants on the multiplication of microorganisms; and 3) genus- or
spe-cies-level analysis of soil nematode communities in and around
upland fields, and investigation of the biological characteristics
of entomopathogenic nematodes. The following activities were
completed in FY 2005.
The Microbial Ecology Unit is investigating the ef-fects of soil
microorganisms on the population dynamics of sclerotium-forming
fungi. In 2005, we focused on the effects of soil fumigation on
soil microbial community. The process of community development
after fumigation was monitored by PCR-DGGE. A nested PCR method was
established for the specific amplification of asco-mycetes, which
are the main component of the soil fun-gal flora. The DGGE patterns
revealed that ascomyce-tous fungi such as Alternaria, Trichoderma,
and Penicil-lium became predominant after fumigation. Their
activ-ity against Fusarium oxysporum f. sp. lactucae was then
studied in potted butterhead lettuce. Of 10 isolates, four
(including a reference antagonist) suppressed disease severity, but
these four isolates failed to minimize popu-lation increase of the
pathogen in the soil. Their re-
sponses to several kinds of nutrients could not be
char-acterized with Biosensor. Isolates of Trichoderma
con-comitantly obtained from Rosellinia necatrix mycelia suppressed
the severity of the disease cause by this fun-gus in Lupinus luteus
planted in sterilized soil but failed to do so in non-sterile
soil.
The Microbial Genetics and Physiology Unit ex-amined
antagonistic activity against various plant para-sitic fungi and
bacteria.
To analyze the behavior of, and colonization by, strains of
fluorescent pseudomonad bacteria antagonistic to Gaeumannomyces
graminis var. tritici, we generated an antagonistic strain
constitutively expressing a green fluorescent protein (GFP) and
investigated its behavior in and on wheat seedlings and their
roots. The antagonis-tic strain colonized the roots, but did not
invade them. Moreover, we investigated the population density of
Bradyrhizobium japonicum MA106 in soils inoculated with the
antagonistic strain to clarify the activity of the strain. The
antagonistic strain did not affect the density of B. japonicum
MA106. These methods and results should be useful for analyzing and
monitoring the be-havior of microorganisms introduced into the
rhizosphere and soil.
To elucidate the true state of diversity of bacteria be-longing
to the family Rhizobiaceae, including Agrobac-terium and Rhizobium
species, we performed a phyloge-netic analysis of a total of 69
strains belonging to, or closely related to, the family
Rhizobiaceae. We used the dnaK, eno, pyrG, recA, and rpoD genes as
markers. The optimum evolutionary model and parameters were
searched by conducting a likelihood ratio test, and phy-logenetic
trees were constructed by using the distance,
Fig. 2 requency distributions of total flight time during a 23-h
experimental period in two lines (collected in 2001 and 2003) of
Ophraella communa, as meas-ured with a flight mill system.
0 0< 1< 10< 60< 120< 180< 240< 300<0
10
20
30
40
Flight time (min)0 0< 1< 10< 60< 120< 180<
240< 300<
0
10
20
30
40
Flight time (min)
2001 2003
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Research Overview and Topics in 2005
42
parsimony, maximum likelihood, and Bayesian methods on the basis
of a selected optimum condition (GTR+G+I). In these trees, members
of the genera Agrobacterium and Rhizobium formed one extremely
monophyletic cluster together with Sinorhizobium and other species
belonging to the family Rhizobiaceae, Blastobacter species, and
pesticide-degrading bacteria. Within this cluster, no ten-dency of
the species to be grouped by their own genera was apparent. Thus,
the species constituting the family Rhizobiaceae are extremely
closely related to one an-other, suggesting that subdivision of
this family into multiple genera is inappropriate.
The Nematology and Soil Zoology Unit compiled a genus-level list
of nematodes—some of which were identified to species level—in a
no-till manure-amended field. The no-till field contained 61 genera
of nematodes and was characterized by genera such as Acrobeles,
Teratocephalus, Monhystrella, Plectus, Wilsonema, and Bastiania,
which are rare or absent in conventionally tilled fields.
From our investigation of the biological characteris-tics of
free-living soil nematodes, three new lines of fungivorous
dorylaimid nematodes belonging to genus Tylencholaimus were
established. Only Filenchus dis-crepans performed well on the
Rosellinia necatrix fungal mat; the other six genera, including
Tylencholaimus parvus and Aphelenchus avenae, showed little
multipli-cation. No nematodes tested showed the ability to act as
vectors for fungal virus within R. necatrix.
Two cultures of bacteriophagous cephalobid nema-todes were also
established. The generation time of one of these was measured,
together with those of two rhab-ditid nematodes and a
cephalobid.
The Microorganism Genebank project was imple-mented by the
related laboratories; it acts as a sub-bank for the MAFF Genebank
system. The purposes of this project are to collect and
characterize microorganisms such as plant-pathogenic
microorganisms, biological control agents, and plant-inhabiting
microorganisms, and then register them with the MAFF Genebank.
In 2005, 153 isolates, such as plant-pathogenic mi-croorganisms
and microorganisms isolated from rice plants, were registered,
including two different species belonging to the genus
Colletotricum, isolated from a single symptomatic leaf of a
hortensia plant. We evalu-ated a total of 972 properties (including
morphology, pathogenicity, physiological characteristics, and
produc-tion of substances antibiotic to fungi or other organisms)
of 324 isolates of the MAFF Genebank. One hundred bacterial
isolates were grown on culture and transferred to the MAFF Genebank
as part of the active collection.
Topic : Application of ecological indices to the evalua-tion of
nematode community changes after soil fumi-gation
Because nematode species differ in terms of food type and life
history traits, their community structures reflect soil
environmental conditions. To describe these structures by a single
value for the purposes of soil as-sessment, some weighted
averagings have been devel-oped, including the Maturity Index (MI)
for physical and chemical disturbances; the Structure Index (SI)
for eco-system development; the Enrichment Index (EI) for
nu-tritional status; and the Channel Index (CI) for the
char-acterization of decomposition pathways. We examined whether
these indices, together with general diversity indices, were good
descriptors of nematode community change after soil fumigation.
Nematode population den-sities and family-level faunal compositions
were inves-tigated for 5 months after chloropicrin fumigation of
soybean fields. After the chemical treatment, the domi-nant
nematode family changed from an extremely r-strategic bacterial
feeder to another bacterial feeder, and in every feeding group
K-strategists were barely detected. In the non-fumigated control
plots the extreme r-strategists still predominated, but the numbers
of K-strategists also increased gradually with time. Among the
ecological indices examined, MI, EI and SI described these
structural changes in the nematode communities (Fig. 1). However,
the replacement of extremely r- strate-gic bacterial feeders with
another bacterial feeder in the plots required careful
interpretation of MI, because the value of this index was
considered lower in disturbed soils. SI was considered a more valid
index than the oth-ers in evaluating appropriately the ecological
status of nematode communities after chemical disturbance: SI
values remained low even 170 days after fumigation, indicating that
the nematode community had not recov-ered. (H. Okada)
4) GMO Assessment Team
The missions of the GMO Assessment Team are: 1) to clarify the
ecological impact of GMOs (genetically modified organisms); 2) to
develop standards of risk as-sessment for GMOs; and 3) to collect
basic information and documents relating to GM and conventional
crops. The major results of our research projects in regard to 1)
and 2) are described as follows. 1) We have been monitoring the
distribution and weedi-ness of GM canola (Brassica napus) around
the Kashima Seaport, which is one of the ports in Japan where
canola seeds are unloaded. We have also conducted further
in-vestigations into the transfer of introduced herbi-cide-tolerant
genes to relatives of B. napus growing in
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43
the area. This study assessed the ecological effects of feral
canola, including herbicide-tolerant GM plants (glyphosate- and/or
glufosinate-tolerant), by focusing on their ability to become
established in various habitats. Feral canola populations were
found in three types of habitat, each of which varied with respect
to soil depth, population spread (linear, planar, or isolated), and
vege-tation cover. These habitats were disturbed land and the
ridges between paddy fields (Type 1); road islands and the areas
beneath trees along sidewalks (Type 2); and spaces between the
paving on curbs and sidewalks (Type 3) (Fig. 2). Canola plants of
various sizes were found throughout the year in Type 1 habitat,
whereas few plants
were found at any time of the year in Type 2 habitat.
Fluctuations in the distribution of canola populations were very
high in Type 3 habitat because of frequent disturbance due to weed
and mud removal. No differ-ences in habitat preference were
detected between GM and non-GM canola because the total number of
plants and the proportion of GM to non-GM canola in mixed
populations exhibited differences in each of the habitats. We
postulated that the population dynamics of both GM and non-GM
canola were more highly dependent upon habitat and ecological
conditions than differences in her-bicide tolerance. 2) There will
be two concerns if GM soybean is to be
Fig. 1 Changes in Maturity Index (MI) (left), Enrichment Index
(EI) (middle), and Structure Index (SI) (right) after fumigation of
soil with chloropicrin. White and black squares are non-fumigated
and fumigated plots, respectively. Horizontal axes indicate days
after fumigation (–1 is 1 day before treatment) and vertical axes
show index values. Vertical bars are standard errors of three
replicates. Index values of fumigated plots with * were
significantly different from non-fumigated plots on the same survey
date (t-test, P < 0.05).
Type 1 Type 2 Type 3 (21, April, 2004) (21, April, 2004) (13,
June, 2004)
Fig. 2 The three types of habitat of Brassica napus around
Kashima Port.
0
0.5
1
1.5
2
2.5
-1 20 59 123 172 Days
***
MI
0
20
40
60
80
100
120
-1 20 59 123 172 Days
*
EI
0
10
20
30
40
50
60
70
-1 20 59 123 172 Days
**
SI
-
Research Overview and Topics in 2005
44
cultivated commercially and widely in Japan. One is the
pollen-mediated dispersal of transgenes from GM soy-beans to
conventional (non-GM) soybeans in neighbor-ing fields. Another is
the gene flow from GM soybeans to wild soybeans (Glycine soja).
Wild soybean is the ancestor of the conventional soybean in East
Asia: both species have the same number of chromosomes, and there
is no barrier to crosses between the two species. However, rates of
spontaneous hybridization among conventional soybeans and between
cultivated and wild soybean are expected to be very low because
they are predominantly self-pollinating species. From 2001 to 2004,
we evaluated the outcrossing rate between GM and non-GM soybeans in
relation to their distances apart
under field conditions. We cultivated glyphosate-tolerant GM
soybeans as pollen donors and conventional soy-beans (non-GM) as
pollen recipients (Fig. 3). A total of 107 846 progeny harvested
from conventional soybeans over a 4-year period were screened for
glyphosate herbi-cide tolerance. The highest outcrossing
rates—0.19% in 2001 and 0.16% in 2002—were found 0.7 m from the
pollen donors. The highest rate in 2004 was 0.052%, found at 2.1 m.
The farthest distances from pollen donors at which hybrid progeny
were found were 7 m in 2001, 2.8 m in 2002, and 3.5 m in 2004. Over
the 4-year period no hybrid progeny were found in the rows 10.5 m
from the pollen donors. (K. Matsuo)
Fig. 3 Field arrangement of GM soybean and non-GM soybean.
Department of Biological Safety
