Agricultural
Communication
Biosci. Biotech. Res. Comm. 10(2): 213-219 (2017)
Abundance of rhabditid nematodes in agricultural soil
of Khorramabad, Iran
Azin Vafa, Ayatollah Saeedizadeh* and Abdolamir Bostani
Faculty of Agriculture, Shahed University, Tehran, Iran
ABSTRACT
This study was undertaken to evaluate the factors affecting the abundance of rhabditid nematodes in the farms of
Khorramabad city of Lorestan province, Iran. Nematode communities as well as rhabditids population reacted to the
soil pH and the type of crops cultivated at each sample point. Crop type affected nematode populations mainly due
to their root systems. Also, the abundance of r habditid nematodes decreased at lower pH of the soil. Since some of
the nematodes are entomopathogenic hence, results of the present study are important in terms of biological control
of soil pests which leads to preservation of agro-ecosystem through less use of chemical pesticides and achievement
of a sustainable agriculture.
KEY WORDS: NEMATODES, ROOT SYSTEM, SOIL PH
213
ARTICLE INFORMATION:
*Corresponding Author: ayatsaeed314@gmail.com
Received 1
st
March, 2017
Accepted after revision 19
th
June, 2017
BBRC Print ISSN: 0974-6455
Online ISSN: 2321-4007 CODEN: USA BBRCBA
Thomson Reuters ISI ESC and Crossref Indexed Journal
NAAS Journal Score 2017: 4.31 Cosmos IF : 4.006
© A Society of Science and Nature Publication, 2017. All rights
reserved.
Online Contents Available at: http//www.bbrc.in/
INTRODUCTION
Rhizosphere soil often contains a variety of soil pests
that are harmful to the host plant. Potentially, chemi-
cal method is the rst choice of farmers to cope with
this problem. However, in addition to forcing heavy
costs, it either endangers the health of human and ani-
mals or has harmful side effects on the environment.
As stated by Brussaard (2012), soil ecosystem services
are bene ts derived from ecosystems that are neces-
sary to maintain soil health and productivity; they are
delivered by the ecosystem functions of soil organ-
isms. Studies have shown that many soil mesofauna,
including nematodes in several trophic levels, are one
or two steps higher in the food chain than microbes.
Also, their generation time is longer than that of the
metabolically-active microbes, making them more tem-
porally stable rather than uctuating with ephemeral
nutrient ushes (Nannipieri et al. 1990) . Furthermore,
nematodes have been widely used as indicators of soil
biodiversity and functioning and as indicators of envi-
ronmental disturbances (Bongers & Ferris 1999; Neher
214 ABUNDANCE OF RHABDITID NEMATODES IN AGRICULTURAL SOIL OF KHORRAMABAD, IRAN BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS
Vafa, Saeedizadeh and Bostani
2001, Ferris et al. 2001; Yeates 2003 Ferris & Tuomisto
2015; Steel & Ferris 2016) .
Soil nematodes play a central role in the soil food web
and linkage to ecological processes therefore, they have
been considered as a tool for testing ecological hypoth-
eses and understanding biological mechanisms in soil
(Neher 2010).Guilds of soil biota are closely associated
with different ecosystem functions. In this regard, Car-
rascosa et al. (2014) reported a positive and signi cant
relationship between soil suppressiveness, soil food web
structure and nematode diversity. Suppression of pest
and disease organisms is an ecosystem service that is the
outcome of the ecosystem function of biological popula-
tion regulation (Brussaard 2012, Steel & Ferris 2016) .
Rhabditid nematodes are an interesting zoological
taxon. They are very abundant in all types of soil and
sediments of freshwater bodies and play important eco-
logical roles mainly as primary consumers their free-
living forms display saprophagous or bacteriophagous
feeding habits but also as animal parasites, in particular
enthomopathogenic forms (Abola a & Peña-Santiago
2003). Previous researches have shown that some soil
physico-chemical characteristics such as texture, pH,
bulk density, soil water potential, temperature, organic
content” can affect the nematodes behavior (Gruner
et al. 2007; FAO, 2017).
However, further investigation is still needed on fac-
tors affecting their population distribution all over the
world (Stuart et al. 2006). Lorestan province with an area
of about 28,392 km
2
(1.7% of the country area) is located
in the south-western Iran at the Zagros Mountain hillside
and is in uenced by the Mediterranean climate. Accord-
ing to statistics released by the Ministry of Agriculture
in 2015, the province is one of the most important cent-
ers of agriculture (535,947 hectares of cultivation area
with 2,169,818 tons of agricultural products). Therefore,
development of biological control in the province could
lead to saving on the costs of agriculture, as well as pro-
tection of the environment.The aim of this research was
to study the abundance of Rhabditid nematodes under
the effect of pH and crop type cultivated in the farms of
Khorramabad city of Lorestan, Iran.
MATERIALS AND METHODS
STUDY SITE AND SOIL SAMPLING
The study site(longitude from 48° 0› to 48° 55’ E and
latitude from 33° 20’ to 33° 42’ N) is located in the
region of the Khorramabad’s agricultural lands, Lorestan
province, Iran (Fig. 1). Samples were randomly taken
from a depth of 15 to 30 cm of rhizosphere soil during
FIGURE 1. Geographical location of the study sitelocated in the region of Khorramabad city (marked with
green on the left side) of Lorestan province (colored in red)
BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS ABUNDANCE OF RHABDITID NEMATODES IN AGRICULTURAL SOIL OF KHORRAMABAD, IRAN 215
Vafa, Saeedizadeh and Bostani
the growing season of September and October. Depend-
ing on each farm area, sampling intervals was varied
from 20 to 25 m. The geographical coordinates as well
as altitude were recorded by a GPS device model Garmin
ETrex Vista HCX (data are not presented). Also, the type
of cultivated crop in each sampling point was recorded.
In total, 175 soil samples were taken from 24 differ-
ent crop types including: alfalfa, apple, apricot, barley,
clover, corn, eggplant, garlic, grape, green beans, mung,
oak, pea, peach, pepper, pomegranate, radish, red beans,
rice, tomato, turnip, vegetable, walnut, wheat. The acid-
ity of the soil samples was also determined in the labo-
ratory by using a pH meter.
NEMATODE EXTRACTION
Nematodes were extracted from soil samples using a
modi ed Baermann funnel procedure (Viglierchio &
Schmitt 1983). For this purpose, plastic trays having a
sieve (mesh no 10) were used. First, trays were lled with
water and covered with a layer of tissue paper. After-
ward, soil samples were spread on tissue paper. After
four days, nematodes were extracted using a sieve (mesh
no 400) from the water and were transferred to Petri
TABLE 1. ANOVA of frequency of nematode
populations studied in some different farms/gardens of
Khoramabad of Lorestan province, Iran.
Mean Square
Source DF Total Nematodes Rhabditids
Type of cultivated
crop
23 4910.86 * 15.06 *
Error 151 2572.58 8.50
Total 174
*signi cant difference at the 0.05 of probability level
TABLE 2. Descriptive statistics related to the frequency of nematode populations studied in some
different farms/gardens of Khoramabad of Lorestan province, Iran.
Type of
cultivated
crop
Number of
studied
farms/
gardens
All nematodes Rhabditid nematodes
Sum Mean ± SE Min Max Sum Mean ± SE Min Max
Alfalfa 9 993 110.33±18.58 ab 27 230 47 5.22±0.81 ab 1 9
Apple 13 1394 107.23±18.4 abc 9 264 44 3.38±0.59 ab 0 7
Apricot 5 523 104.6±18.85 abc 53 157 22 4.4±1.5 ab 1 10
Barley 25 2257 90.28±10.57 abc 8 205 82 3.42±0.6 ab 0 10
Clover 7 593 84.71±16.16 abc 16 146 32 4.57±1.56 ab 0 13
Corn 16 1894 118.38±14.37 ab 30 288 67 4.19±0.44 ab 2 7
Eggplant 7 528 75.43±9.34 abc 43 104 21 3±0.72 ab 1 7
Garlic 2 46 23±18 c 5 41 2 1±1 b 0 2
Grape 7 426 60.86±18.33 abc 3 136 20 2.86±1.08 ab 0 8
Green beans 3 129 43±16.77 bc 13 71 4 1.33±0.88 b 0 3
Mung 6 391 65.17±11.99 abc 18 97 20 3.33±0.56 ab 1 5
Oak 6 331 55.17±15.9 abc 4 100 6 1±0.37 b 0 2
Pea 3 112 37.33±4.91 bc 31 47 8 2.67±0.88 ab 1 4
Peach 2 236 118±75 ab 43 193 10 5±3 ab 2 8
Pepper 3 322 107.33±22.7 abc 62 132 8 2.67±1.33 ab 0 4
Pomegranate 3 280 93.33±22.58 abc 56 134 10 3.33±1.33 ab 2 6
Radish 2 228 114±38 ab 76 152 13 6.5±0.5 a 6 7
Red beans 2 75 37.5±5.5 bc 32 43 3 1.5±0.5 b 1 2
Rice 8 336 42±15.59 bc 2 122 5 0.71±0.42 b 0 3
Tomato 5 403 80.6±11.95 abc 58 122 16 3.2±0.73 ab 1 5
Turnip 12 1562 130.17±12.05 a 36 188 78 6.5±1.25 a 1 16
Vegetable 6 500 83.33±17.69 abc 43 152 11 1.83±0.54 ab 0 3
Walnut 2 230 115±30 ab 85 145 9 4.5±0.5 ab 4 5
Wheat 21 1883 89.67±13.52 abc 10 247 80 3.81±0.99 ab 0 18
Means have been compared using Duncan multiple range method.
Means with the same letter are not signi cantly different.
216 ABUNDANCE OF RHABDITID NEMATODES IN AGRICULTURAL SOIL OF KHORRAMABAD, IRAN BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS
Vafa, Saeedizadeh and Bostani
FIGURE 2. Dendrogram obtained based on complete linkage method and Euclidean similarity matrix
by using data recorded for abundance of all nematodesas well asRhabditid nematodes in some differ-
ent farms/gardens of Khoramabad of Lorestan province, Iran. Dnedrogram was drawn using Minitab
software.
dishes. The total number of nematodes as well as the
number of Rhabditids were counted using a stereomicro-
scope at 40x of magni cation. Statistical analyses were
carried out using SAS, Excel and Minitab software.
RESULTS AND DISCUSSION
ASSOCIATION BETWEEN NEMATODE
ABUNDANCE AND CROP TYPE
Soil ecosystem functioning is of topics in ecological and
agricultural studies (Steel & Ferris 2016). Researches
have shown that plant composition, soil properties, and
microclimates cause changes in composition and struc-
ture of nematode populations among soil ecosystems
(Neher 2010). The results of counting nematodes revealed
that the overall mean abundance of all nematodes in the
study site was 89.33±3.94 nematode per 100 g of the
soil (n = 175). Also, the mean abundance of Rhabditid
nematodes was 3.55±0.23 nematode per 100 g of the
soil. According to this result, approximately 4% of the
total population of assayed nematodes belonged to the
Rhabditids. This ratio was 7.12% (highest) for pea and
1.70% (lowest) for rice. One way ANOVA showed that
the abundance of all nematode types as well as Rhab-
ditid nematodes was statistically signi cantly different
among studied crop types (Table 1).
Averagely, the highest and lowest mean abundance
of all nematodes was found in the rhizosphere soil of
farms of turnip (130.17±12.05, n=12) and garlic (23±18,
TABLE 3. Properties of clusters obtained on the basis of data recorded for Nematode and Rhabditids abundance
in some different farms/gardens of Khoramabad of Lorestan province, Iran.
Cluster Number of
observations
Cluster membership (crop type) All nematodes
mean ± SE
Rhabditid nematodes
mean ± SE
1 9 Alfalfa, Apple, Apricot, Corn, Peach, Pepper,
Radish, Turnip, Walnut
114.16±2.53 4.71±0.43
2 10 Barley, Clover, Eggplant, Grape, Mung, Oak,
Pomegranate, Tomato, Vegetable, Wheat
77.85±4.20 3.02±0.31
3 5 Garlic, Green beans, Pea, Red beans, Rice 36.57±3.58 1.43±0.34
Cluster analysis has been carried out using complete linkage method and Euclidean similarity matrix
BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS ABUNDANCE OF RHABDITID NEMATODES IN AGRICULTURAL SOIL OF KHORRAMABAD, IRAN 217
Vafa, Saeedizadeh and Bostani
n=2), respectively. Also, the highest and lowest mean
abundance of Rhabditid nematodes belonged to radish
(6.5±0.5, n=2) and rice (0.71±0.42, n=8), respectively
(Table 2). The result revealed that rice rooting system
and/ or paddy soil was not a suitable environment for
reproduction and growth of Rhabditida nematodes. Also,
it seems that glandular root system provided a more
suitable environment for the growth and mobility of
Rhabditid nematodes than a super cial root system.
As demonstrated earlier, crop type affects the soil
ecosystem in different ways. For instance, breeding pro-
grams for improving yield lead to the introduction of
new high-yielding varieties. Such modi ed crops have
a high potential of absorption of minerals from the soil
as well as higher photosynthetic capacity that affect
the quantity and quality of nutrients and energy ow-
ing through the soil (Neher 2010). Also, plant life cycle
has been known as another factor affecting soil ecosys-
tem. Perennial crops have a more extensive root web
and rooting depth than annual crops leading to sup-
port a soil community with many omnivores and preda-
tors. Populations of terrestrial ecosystems in perennial
crops is more similar to that of natural soil ecosystem
as compared to annual crops (Freckman & Ettema 1993;
Neher & Campbell 1994). Wardle et al. (2003), believe
that plant species have greater effects on microbes and
FIGURE 3. The effect of pH on mean abundance of all nematode types (above) and Rhab-
ditid nematodes (below) per 100 g of the soil extracted from some different farms of
Khoramabad city of Lorestan province, Iran.
218 ABUNDANCE OF RHABDITID NEMATODES IN AGRICULTURAL SOIL OF KHORRAMABAD, IRAN BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS
Vafa, Saeedizadeh and Bostani
plant-parasitic nematodes than they do on predatory
nematodes. Moreover, rooting pattern of different func-
tional groups of plants (i.e., legumes, forbs) constructs
habitats which are more favorable to some species of
nematodes than others (Neher 2010). Furthermore, Pis´
kiewicz et al. (2008) reported that communities of plant-
parasitic nematodes can be complex within the rhizos-
phere of a single plant species. Such as those obtained
in this study, the above reports con rm that there are
signi cant differences in soil ecosystems arising from
various crops cultivation.
Figure 2 shows the results obtained from cluster
analysis of 24 different crops based on nematode abun-
dance observed in each cultivated crop. On this basis,
studied crops were classi ed into 3 groups. The aver-
age abundance of nematodes along with the standard
error corresponding to each group has been shown
in Table 3. Clusters 1, 2 and 3 had 9, 10 and 5 mem-
bers, respectively. The highest frequency of nematodes
belonged to cluster 1 where some crops such as alfalfa,
apple, apricot, corn, peach, pepper, radish, turnip and
walnut were grouped in it. Also, cluster 3 comprising
of garlic, green beans, pea, red beans and rice had the
lowest frequency of nematodes (Table 3). With respect
to the members of cluster 1 “which had the highest
abundance of Rhabditid nematodes” it can be concluded
that the root systems arisen by perennial crops (alfalfa),
glandular plants (turnip, radish) and trees (apple, apri-
cot, peach, walnut) were more favorable for Rhabditid
nematodes. Therefore, in agreement with Freckman &
Ettema (1993) and Neher (2010), the result showed that
perennial plants had an impact on Rhabditid nematodes
population.
EFFECT OF SOIL PH ON NEMATODE
ABUNDANCE
Data obtained from the study showed that soil pH in the
area of study ranged from 6.5 (Grape) to 8.16 (Vegetable)
(Table 4). Figure 2 shows mean abundance of nematodes
at different amounts of pH of the soil. Results revealed
that the mean abundance of nematodes rose up in soils
TABLE 4. The pH measured in the soil cultivated with various crops in
different farms of Khoramabad city of Lorestan province, Iran.
Crop type pH
Mean Standard error Minimum Maximum Count
Apricot 7.16 0.21 6.51 7.66 5.00
Grape 7.18 0.15 6.50 7.55 7.00
Radish 7.21 0.09 7.12 7.30 2.00
Rice 7.22 0.07 6.99 7.60 8.00
Green beans 7.28 0.31 6.65 7.60 3.00
Garlic 7.29 0.01 7.27 7.30 2.00
Peach 7.31 0.11 7.20 7.42 2.00
Tomato 7.33 0.02 7.30 7.40 5.00
Barley 7.33 0.04 6.90 8.01 25.00
Mung 7.36 0.08 7.01 7.57 6.00
Corn 7.41 0.09 6.64 7.97 16.00
Alfalfa 7.41 0.09 7.00 7.66 9.00
Pea 7.42 0.19 7.07 7.70 3.00
Wheat 7.44 0.06 7.10 8.00 21.00
Eggplant 7.47 0.14 7.00 8.00 7.00
Turnip 7.48 0.10 7.02 8.06 12.00
Clover 7.52 0.10 7.30 8.06 7.00
Apple 7.56 0.11 6.65 8.05 12.00
Pepper 7.57 0.13 7.30 7.70 3.00
Red beans 7.58 0.13 7.45 7.70 2.00
Pomegranate 7.65 0.05 7.60 7.74 3.00
Oak 7.67 0.11 7.34 8.10 6.00
Walnut 7.68 0.20 7.48 7.87 2.00
Vegetable 7.78 0.09 7.50 8.16 6.00
BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS ABUNDANCE OF RHABDITID NEMATODES IN AGRICULTURAL SOIL OF KHORRAMABAD, IRAN 219
Vafa, Saeedizadeh and Bostani
with slightly alkaline property (soil pH more than 7). The
average frequency of Rhabditid nematodes in the soil
with pH more than 8 was numerically higher than that
of 7-8. However, this superiority was not statistically
signi cant. In general, results of this study showed that
the nematode populations signi cantly decreased at the
soil pH less than 7.
As described by Garbeva et al. (2004) and Šalamún
et al. (2014), changes in soil pH could have led to direct
and indirect effects on the nematode community. Like-
wise, results of this study revealed that the abundance of
Rhabditid nematodes decreased at lower pH of the soil.
Korthals et al. (1996), believe that a lower pH enhances
the toxicity of heavy-metals through increase of their
adsorption to the soil.
Korthals et al. (1996), have shown that nematodes
exchange several ions through their cuticle in order to
regulate their osmotic pressure. It has been suggested that
soil acidi cation can lead to increasing ion concentra-
tions in the soil pore water to such an extent that nema-
todes might experience problems in regulating their water
status. They also stated that, soil pH indirectly affected the
nematode community by in uencing food availability, by
interfering with the competitive interactions between spe-
cies, or by affecting the abiotic environment.
In conclusion, results of the present study indicated that
crop type as well as soil pH could affect Rhabditid nema-
todes communities. The outcome is important in terms of
biological control of soil pests which leads to preservation
of agro-ecosystem through less use of chemical pesticides
and achievement of a sustainable agriculture.
REFERENCES
Abola a, J., Peña-Santiago, R. (2003): Nematodes of the
Order Rhabditida from Andalucía Oriental, Spain. The Gen-
era Nothacrobeles Allen &Noffsinger, 1971 and Zeldia Thorne,
1937. Journal of nematology 35:233
Bongers, T., Ferris, H. (1999): Nematode community structure
as a bioindicator in environmental monitoring. Trends in Ecol-
ogy & Evolution 14:224-228
Brussaard, L. (2012): Ecosystem services provided by the soil
biota. Soil Ecology and Ecosystem Services. Oxford University
Press, Oxford, UK 45-58
Carrascosa, M., Sánchez-Moreno, S., Alonso-Prados, J. (2014):
Relationships between nematode diversity, plant biomass,
nutrient cycling and soil suppressiveness in fumigated soils.
European Journal of Soil Biology 62:49-59
FAO (2017): Soil Organic Carbon: the hidden potential. Food
and Agriculture Organization of the United Nations Rome, Italy
Ferris, H., Bongers, T., De Goede, R. (2001): A framework for
soil food web diagnostics: extension of the nematode faunal
analysis concept. Applied Soil Ecology 18:13-29
Ferris, H., Tuomisto, H. (2015): Unearthing the role of bio-
logical diversity in soil health. Soil Biology and Biochemistry
85:101-109
Freckman, D.W., Ettema, C.H. (1993): Assessing nematode
communities in agroecosystems of varying human interven-
tion. Agriculture, Ecosystems & Environment 45:239-261
Garbeva, P.v., Van Veen, J., Van Elsas, J. (2004): Microbial
diversity in soil: selection of microbial populations by plant
and soil type and implications for disease suppressiveness.
Annu. Rev. Phytopathol. 42:243-270
Gruner, D.S., Ram, K., Strong, D.R. (2007): Soil mediates the
interaction of coexisting entomopathogenic nematodes with
an insect host. Journal of Invertebrate Pathology 94:12-19
Korthals, G.W., Bongers, T., Kammenga, J.E., Alexiev, A.D.,
Lexmond, T.M. (1996): Long‐term effects of copper and ph on
the nematode community in an agroecosystem. Environmental
Toxicology and Chemistry 15:979-985
Nannipieri, P., Grego, S., Ceccanti, B. (1990): Ecological sig-
ni cance of the biological activity in soil. Soil biochemistry.
Volume 6. 293-355
Neher, D.A. (2001): Role of nematodes in soil health and their
use as indicators. Journal of nematology 33:161
Neher, D.A. (2010): Ecology of plant and free-living nematodes
in natural and agricultural soil. Annual review of phytopathol-
ogy 48:371-394
Neher, D.A., Campbell, C.L. (1994): Nematode communities and
microbial biomass in soils with annual and perennial crops.
Applied Soil Ecology 1:17-28
Pi
s´kiewicz, A.M., Duyts, H., van der Putten, W.H. (2008):
Multiple species-speci c controls of root-feeding nematodes
in natural soils. Soil Biology and Biochemistry 40:2729-
2735
Šalamún, P., Kucanová, E., Brázová, T., Miklisová, D., Rencˇo,
M., Hanzelová, V. (2014): Diversity and food web structure of
nematode communities under high soil salinity and alkaline
pH. Ecotoxicology 23:1367-1376
Steel, H., Ferris, H. (2016): Soil nematode assemblages indi-
cate the potential for biological regulation of pest species. Acta
Oecologica 73:87-96
Stuart, R.J., Barbercheck, M.E., Grewal, P.S., Taylor, R.A., Hoy,
C.W. (2006): Population biology of entomopathogenic nema-
todes: Concepts, issues, and models. Biological Control 38:80-
102
Viglierchio, D., Schmitt, R.V. (1983): On the methodology of
nematode extraction from eld samples: Baermann funnel
modi cations. Journal of nematology 15:438
Wardle, D.A., Yeates, G.W., Williamson, W., Bonner, K.I. (2003):
The response of a three trophic level soil food web to the iden-
tity and diversity of plant species and functional groups. Oikos
102:45-56
Yeates, G.W. (2003): Nematodes as soil indicators: functional
and biodiversity aspects. Biology and Fertility of Soils 37:199-
210