The vertical migration of M. incognita juveniles introduced at 20 cm from the roots was studied in five natural soils, 100% silica sand, 95% silica sand with 5% clay, 90% silica sand with 10% clay, and 95% silica sand with 5% clay as a concentrated layer. In natural soils the percentage of juveniles capable of migrating 20 cm and penetrating the roots decreased when the percentage of clay and silt increased. No migration occurred in silica sand without clay particles; when 5 or 10% of clay were mixed to silica sand, 34 and 26%, respectively, of the juveniles were able to migrate 20 cm. Clay separated from silica sand in which tomatoes were grown was attractive for juveniles. It is suggested that clay particles aid in the migration of root-knot juveniles over long distances to plant roots by absorbing and holding root exudates or bacterial by-products which form a concentration gradient enabling nematodes to locate roots

Prot, Jean-Claude

Van Gundy, S. D.

PubMed

Van Gundy, S.D.

Name not available

Effect of soil texture and the clay component on migration of Meloidogyne incognita second-stage juveniles

Horizon / Pleins textes

I 
Reprinted from April 19811 JOURNAL OF NEMATOLOGY, Volume 13, No. 2 
Published by the Society bf Nematologists, Joseph A. Veech, Editor-in-Chief 
U.S. Department of Agriculture, College Station, Texas 77840 
Effect of Soil Texture and the Clay Component on 
Migration of Meloidogyne incognita Second-stage Juveniles 
Jean-Claude Prot and S. D. Van Gundyl 
Abstract: The vertical migration of M .  incognita juveniles introduced at 20 cm from the roots 
was studied in live natural soils, 100% silica sand, 95% silica sand with 5% clay, 90% silica sand 
with 10% clay, and 95yo silica sand with 5% clay as a concentrated layer. In natura1 soils the 
percentage of juveniles capable ol: migrating 20 cin and penetrating the roots decreased when the 
percentage of clay and silt increased. No migration occurred in silica sand without clay particles; 
when 5 or 10% of clay were mixed to silica sand, 34 and %O/,, respectively, of the juveniles were 
able to migrate 20 cm. Clay separated from silica sand in which tomatoes were grown was attrac- 
tive for juveniles. I t  is suggested that clay particles aid in the migration of root-knot juveniles 
over long distances to plant roots by absorbing and holding root exudates or bacterial by-products 
which form a concentration gradient enabling nematodes to locate roots. Key words: attraction, 
nematode movement. 
Soil texture and pore size influence 
the migration of plant-parasitic nematodes. 
Rode (9) showed that the migration of juve- 
niles of Globodera rostochiensis (Wollen- 
weber) Stone toward potato plants was 
greatest in sandy soil, intermediate in loamy 
soil, and least in clay soil. Tarjan (12) ob- 
_- served that Rudofiholus similis (Cobb) 
Thorne moved better in sandy soil than in 
heavy-textured soil. Baines (2) suspected 
that the low iyfection of sweet orange seed- 
lings by Tylenchulus semifienetruns Cobb 
in coarse sand may have been caused by 
limited juvenile migration in this soil. 
Wallace (14,15) suggested that there was an 
optimum particle size for the movement of 
each nematode species in soil. 
A factor responsible for stimulating or 
attracting nematodes left in the soil after 
culture of host plants has been reported for 
Meloi$ogyne hafila (16), Meloidogyne sp. 
(7), and Hemicycliophora fiaradoxa (6). 
Luc (5 )  suggested that this factor was ab- 
sorbed on the clay fiaction. Viglierchio (13) 
suggested that a stimulus for repulsion was 
absorbed on soil colloids. 
T o  determine the influence of soil tex- 
ture on the migration of second-stage juve- 
niles of M.  incognita (Ibfoid & White) 
Chitwood towards a tomato plant, we 
studied their ability to move vertically in 
five different natural soils, in pure silica 
sand, and in three different mixtures of 
silica sand and clay. The movement of M.  
incognita juveniles was studied in the pres- 
' 
I-' 
Receiped for publication 21 April 1980. 
1Department of Nematology, University of California, 
Riverside, CA 92521. Current address of senior author: 
Laboratoire de Nématologie, ORSTOM, B.P. 1386, Dakar, 
Sénégal. 
ence or absence of clay in which plants had 
been grown to determine the nature of ad- 
sorption of the stimulant. 
MATERIALS AND METHODS 
All the juveniles of M.  incognita used in 
these experiments were derived from a cul- 
ture maintained on (Lycofiersicon esculen- 
tuin L. cv. Tropic) tomato in the green- 
house. Only individuals not more than 48 h 
in age after hatching and extracting in a 
mist chamber were used for testing migra- 
tion abilities. 
Vertical migrations of juveniles of M.  
incognita were studied using the experi- 
mental apparatus described previously (8). 
A polyvinyl chloridel (PVC) tube 21 cm long 
with an internal diameter of 2 cm was filled 
with soil. Three hundred juveniles were 
introduced into the soil 1 cm from the bot- 
tom of the tube which was then closed with 
a polyethylene film. The top of the tube was 
covered with a 85-pm screen and inserted 
into a hole made in the center of the bottom 
of a 150-cm3 Styrofoam cup. Approximately 
130 cm3 of the same soil was placed in the 
cup with a 4-wk-old tomato seedling. With-, 
this apparatus, vertical migration of M.  
incognita juveniles was studied in five differ- 
ent steam sterilized natural soils, in pure 
silica sand (particle size 5 250 pm), and 
in three different mixtures of silica sand and 
clay (modeling clay): (i) 95.% silica sand 
with 5 % clay added and thoroughly mixed: 
(ii) 90% silica sand with 10% clay; and 
(iii) silica sand with 5 % clay as a ring at the 
bottom of the cup but not between the roots 
and the tube. The percentage of clay and 
silt in five natural soils is shown in Table 1. 
\ 
-__ 
214 Journal of Nematology, Volume 13, No. 2, April 1981 
The experiments were conducted in a 
growth chamber at a constant temperature 
of 26 C for 7 d. Tomato plants were then 
washed gently from the pots and their en- 
tire root systems were stained with 0.05% 
cold cotton blue-lactophenol (4). Only the 
juveniles that had migrated up the 20-cm 
column and penetrated into the roots were 
counted and recorded. 
In experiments with the five natural soils 
there were 10 replications for each soil type 
and the experiment was repeated three 
times. Experiments in silica sand and mix- 
tures of silica sand and clay were repeated 
four times and there were five replications 
for each soil type. 
The penetration of 4-wk-old tomato 
roots by M .  incognita juveniles was studied 
in three different soil types: pure silica sand 
(particle size 2250 pm) and two natural 
soils containing 14 or 22% clay plus silt. 
This study was conducted in Styrofoam cups 
without the 20-cm column. Three hundred 
juveniles were added to the soil through 
holes just after the tomato seedling was 
transplanted. The plants were removed 
from the pots and their root systems stained 
after 3, 5, and 7 d. There were 10 replica- 
tions for each soil and time interval. 
T o  determine whether attractive or re- 
pellent substances were absorbed on the 
clay, ten 4-wk-old tomato seedlings were 
grown in a pot containing 600 g of silica 
sand and 90 g of clay as a layer at the bot- 
tom of the pot. After 4 or 6 d of tomato 
growth this clay was removed and used in 
an experiment employing PVC tubes 12.5 
cm long with an internal diameter of 2 cm 
and closed at both ends by a polyethylene 
film. At the middle of the tube a 0.3-cm-d 
opening was made for introducing the 
nematodes. The tubes were cut halfway 
every 2.5 cm, allowing division of the col- 
umn of sand in the tube into five fractions 
of 2.5 cm. During the experiments the cuts 
were closed with adhesive tape. Sections 1, 
2, and 3 of the tube were filled with 95% 
silica sand plus 5% clay which had not 
supported the growth of tomato plants. Sec- 
tions 4 and 5 were filled with 95% silica 
sand plus 5 % clay which had grown tomato 
seedlings previously. Fifteen percent water 
by weight ivas added to the mixture of sand 
and clay. Immediately after preparing the 
sand tube, 0.1 ml of water containing 300 
juveniles was introduced with a syringe 
into the center of section 3 of the column. 
The tubes were maintained horizontally a t  
26 C and divided into five parts 48 h after 
introduction of the juveniles. Nematodes 
were extracted by placing the sand from 
each section in a Baermann funnel (1) for 
48 h. 
The experiments using a clay which had 
supported tomato growth for 4 d had six 
replications and were repeated six times. 
The experiments using clay which had sup- 
ported the tomato growth for 6 d were re- 
peated three times with 12 replications the 
first time and 10 replications the second 
and third times. The experiments were also 
repeated six times with four replications 
with each tube filled with silica sand mixed 
with 5 %  of clay which had not supported 
tomato growth. 
A similar set of experiments was con- 
ducted using bentonite instead of modeling 
clay. Ten 4-wk-old tomato plants were 
grown for 7 d in a pot containing 150 g of 
silica sand and 10 g of bentonite as a layer 
at the bottom of the pot. After 7 d of tomato 
growth the bentonite was mixed with silica 
sand. Four hundred grams of silica sand was 
added to 10 g of bentonite with 30 g of 
water adsorbed on the bentonite layer and 
another 55 g of water was added. This mix- 
ture of sand and bentonite was used in an 
experiment in PVC tubes 6 cm long and 
divided in three sections of 2 cm each. The 
bentonite used in sections 1 and 2 had not 
supported plant growth, but that used in 
section 3 had grown tomato for 7 d. The 
control tubes used bentonite which had not 
been used for tomato growth in all three 
sections. Immediately after preparing the 
sand tube we introduced 150 juveniles in 
0.1 ml of water into the center of section 2. 
The tubes were maintained horizontally at 
26 C. Forty-eight hours after introduction of 
the juveniles the sand was divided into three 
parts. The nematodes were extracted from 
the sand as described previously. The ex- 
periment was repeated three times with ten 
replications. 
RESULTS 
The percentage of juveniles able to 
migrate 20 cm and penetrate tomato roots 
Table 1. Migration of Meloidogyize incognita 
juveniles toward tomato roots in five different soil 
types. 
Soil Texture and Migration: Prot, Van Gundy 215 
% 
% clay & 
migration 
Soil type % clay % silt & silt penetration 
1 8.8 5.2 14.0 31.5 a 
2 10.2 11.9 22.1 12.6 b 
3 9.2 16.0 25.2 9.5 b 
4 13.2 19.5 32.7 o c  
5 12.5 23.5 42.0 o c  
Numbers followed by same letter are not signif- 
icantly different, according to an analysis of variance 
(P = 0.05). 
decreased as the percentage of clay and silt 
increased (Table 1). There was a significant 
difference in the rate of migration in soil 
which contained only 14% clay plus silt 
and in soils which contained 22.1 and 
25.2% clay plus silt. No migration was ob- 
served when the soils contained more than 
30% clay plus silt. In  pure silica sand less 
than 1% of the juveniles migrated 20 cm 
and penetrated (Table 2). When 5% clay 
as added to the silica sand the percentage of 
migration was more than 30%, and with 
10% clay the percentage of migration was 
26.4%. When 5 % clay was added as a layer 
at the bottom of the pot, but not between 
Table 2. Migration of Meloidogyite incognita 
juveniles toward tomato roots "in four different soil 
types. 
% 
migration 
% % % clay 
Soil type clay silt & silt penetration 
sand 
250 ,u O O O 0.5 a 
sand 
250 ,u 5 O 5 34.4 b 
sand 
250 ,u 10 O 10 26.4 b 
sand as 
a layer 
250 ,u 5 O 5 0.6 a 
Numbers followed by same letter are not signif- 
icantly different, according to an analysis of variance 
(P = 0.05). 
the roots and the tube, the percentage of 
migration was similar to the all-sand system. 
No differences in penetration (Table 3) 
were observed in two natural soils and in 
pure silica sand when the juveniles were 
introduced directly into the pot around the 
tomato roots for 3, 5, and 7 d. 
In a tube of sand mixed with 5% clay 
which had not been used to grow a tomato 
plant, the juveniles were equally distributed 
on both sides of the tube 48 h after their 
introduction into the center of the tube 
(Fig. 1A). When the reference clay in sec- 
tions 4 and 5 was replaced by clay used to 
grow tomato plants, the juveniles were 
mainly aggregated in sections 4 and 5 con- 
taining the clay used to grow tomato plants 
for 4 d (Fig. 1B) or 6 d (Fig. IC). The 
numbers of juveniles found in the two sides 
of these tubes were significantly different. 
The same results were observed when bento- 
nite was used as the clay fraction (Fig. 2). 
DISCUSSION 
Soil texture appears to be important for 
vertical migration of juveniles of M. incog- 
nita. These differences in migration in soils 
of different structure could occur because 
nematode species generally have an- op- 
timum particle size for movement (15). 
This could explain in part the greater 
pathogenicity of the genus Meloidogyne in 
sandy soils (10,ll) and the quick reinfesta- 
tion that is sometimes observed in a sandy 
soil as nematodes move upward after a poor 
soil fumigation (Van Gundy aiid Lem- 
bright, personal communication). 
The fine particles of clay and slit appear 
to be obstacles to Meloidogyne migration, 
but the clay particles also appear to have a 
function in attracting nematodes over large 
Table 3. Penetration of tomato roots by Meloido- 
gyne incognita juveniles in three different soil types. 
% "Y % penetration after 
Soil types & silt 3 d  5 d  7 d  
1 14 48.6 81.4 77 
2 22.1 ,' 35.2 51.5 ,67.9 
sand 
250 p 
216 Journal of Nematology, Volume 13, No. 2, April 1981 
u) 1 2  
W 
> 
53 
-3 
LI 
O 
z 
O 
5 
3 4 5  
B I 
LI 
O 
5 
C 
1 2 3 4 5  
SECT I ON S 
Fig. 1. Distribution of juveniles of M.  incognita, 
48 h after their introduction at the center of section 
3, in columns of sand mixed with A) 5% clay which 
had not been used to grow tomato plants: and B, 
C) 501, clay which had not been used to grow tomato 
plants in sections 1, 2, and 3 and 5% clay used to 
grow 10 tomato plants for 4 d (B) or 6 d (C) in 
sections 4 and 5. 
distances in soil. The addition of only 5% 
clay increased migration markedly over that 
in pure sand. I t  is difficult to conceive that 
the addition of 5 ’% of clay could change the 
soil texture sufficiently to explain this effect. 
It is possible that the clay particles added to 
the silica sand cause migration of root-knot 
juveniles over large distances to plant roots 
by holding some root exudate either on the 
clay or in a water film and establishing a 
gradient which helps nematodes to locate 
roots. 
I t  is also possible that some root exu- 
dates, carried by soil water, are metabolized 
2 3 
B 
5 
I 2 3 
SECT IONS 
Fig. 2. Distribution of juveniles of M .  incognita 
48 h after their introduction in the center of section 
2: A) in a column of sand mixed with 2.5% bento- 
nite which was not used to grow tomato plants; E) 
in a column of sand mixed with 2.5% bentonite not 
used to grow tomato plants in sections 1 and 2 and 
with 2.5% bentonite used to grow 10 tomato plants 
for 7 d in section 3. 
by the bacteria living on the clay particles 
and that gradients of these byproducts could 
attract the nematodes to the roots. The clay 
particles may also transform or select some 
of the root exudates carried by the percolat- 
ing water. Bird (3) observed that Meloido- 
gyne juveniles were not attracted by tomato 
root exudates, but when these exudates were 
absorbed on anionic exchange resin they be- 
come attractive. 
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1. Baermann, G. 1917. Eine einfache Methode 
zur Auffindung von Ankylostomum (Nematoden) 
Larven in Erdproben. Geneek. Tijdschr. Ned.-Indie 
2. Baines, R. C. 1974. The effect of soil type on 
57:131-137. 
movement and infection rate of larvae of Tylen- 
chulus semipenetrans. J. Nematol. 6:60-62. 
3. Bird, A. F. 1959. The  attractiveness of roots 
to the plant parasitic nematodes Meloidogyne 
javanica and M. hapla. Nematologica 4:322-335. 
4. Guiran, G. de. 19G7. Coloration des nématodes 
dans les tissus végétaux par le bleu coton B froid. 
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5. Luc, M. 1961. Note priliminaire sur le dC- 
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- 1  
Soil Texture and Migation: Prot, Van Gundy 217 
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sitic nematodes by plant root emanations. Phyto- 
pathology 51:136-142. 
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A-77. 


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Effect of Soil Texture and the Clay Component on Migration of Meloidogyne incognita Second-stage Juveniles

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