Cohn, E.

Mor, M.

Horizon / Pleins textes

Morphology and parasitism of the  mature female of 
Rotylenchulus macrosomus(l) 
Eli COHN and Mishael MOR (MORDECHAI) 
Department of Nematology, 7Xe Volcani Center, Bet Dagan, Israel. 
S U W Y  
The mature  female  of Rotylenchulus macrosomus, hitherto  unknown,  was  discovered in  the vicinity of the  type  locality,  and 
its  morphology  and  parasitism  were  studied in comparison  with R. renifonnis. Morphologically, R. nzacrosomus differed  from R. 
renifomzis in  its  greater  body  length,  more  convoluted  body  posture,  more  anteriorly  situated  vulva,  and  more  pointed  tail  terminus. 
R. nlacrosomus was found  to  reproduce on a  number of  vegetable  crops but,  notably, did-not  attack Cotton,  which i s  very  sensitive 
to R. renifomzis. On  a  common  host,  soybean, the two species  induced  a  similar  reaction, viz., an  enlarged  endodermal  feeding  cell 
within  which  a  feeding  tube  was  formed,  and  a  syncytium  comprising  more  or  less  intact  hypertrophied  pericyclic  cells,  with ce11 
Wall breakdown  in  the  region  close  to the nematode  head. The resemblance  between the  mature  females of R. macrosomus and 
R. borealis is  emphasized  and the  general similarity between  these two species  also  in  their  male  and  immature  female  forms,  host 
preferences,  and  host  tissue  reactions  is  shown. 
RÉSUMÉ 
Morphologie et parasitisme de la femelle mature de Rotylenchulus  macrosomus 
La femelle  mature  de Rotylenchulus macrosomus, non observée  jusqu'à  présent,  a  été  découverte à proximité  du  lieu type de 
l'espèce.  Sa  morphologie et son  parasitisme  ont  été  étudiés  et  comparés à ceux  de R. renifonnis. Morphologiquement, R. macrosomus 
diffère  de  R. renifonnis par  un  corps  plus  long  et  plus  convoluté,  la  vulve  située  plus  antérieurement  et  l'extrémité  de  la  queue 
plus  pointue. R. macrosomus se reproduit  sur  de  nombreuses  plantes  maraîchères,  mais  il  est à remarquer  qu'il  n'attaque  pas  le 
cotonnier,  plante  très  sensible à R. renifonnis. Chez  le  soja,  plante-hôte  commune  aux  deux  espèces,  celles-ci  induisent  des  réactions 
similaires : une grande  cellule  nourricière  endodennique  dans  laquelle se forme  le  tube  nutritif  et  un  syncytium  composé  de  cellules 
péricycliques  hypertrophiées  plus ou moins  intactes,  avec  des  ruptures  de  la  paroi  cellulaire  dans  la  région  voisine  de  la  tête du 
nématode.  La  ressemblance  entre  les  femelles  matures  de R. macrosomus et de R. borealis est  soulignée,  de  même  que  la  similarité 
générale  entre  ces  deux  espèces, y compris  mâles,  femelles  immatures,  gamme  d'hôtes  et  réactions  de  l'hôte. 
Rotylenchulus macrosomus Dasgupta, Raski & Sher, 
1968  was described from a population comprising males, 
immature females and ' juveniles, recovered from soil 
in  an olive (Olea europaea L.)  grove in Hulda, Israel; it 
was identified also in several additional habitats and lo- 
cations in Israel (Dasgupta, Raski & Sher,  1968). Popu- 
lations of the species containing mature females were 
detected on olive roots in two groves located within 
30 km of the type locality; this provided an 'opportunity 
to describe the adult female stage, study the host-para- 
site relationships of the species, and reassess its re- 
lationship to other species  within the genus. 
Materials  and  methods 
Soil from around infected  olive  trees, containing 
free-living  stages  of R. macrosomus, was potted, and  the 
nematode population was  allowed to build up  on rooted 
olive cuttings in a growth chamber. After a three-month 
growth period males, immature and mature females 
were extracted from the soil and roots by standard 
techniques and their morphology and measurements 
were compared with those of  a population of R.  renifor- 
mis reared on soybean under  the same conditions. 
Limited host range studies of R. macrosomus were 
carried out on Cotton (Gossypium barbadense L.) CV. 
Acala, tomato (Lycopersicon  esculentum Mill.)  cv. Hosen 
Eilon, snap  bean (Phaseolus'vulgaris L.) cv. Contender, 
Sour orange (Citrus  aurantium L.), corn (Zea mays L.) 
cv. N-170, soybean (Glycine hispida Max.) cv. Lee, 
sorghum (Sorghum vulgare Pers.) cv. D-2052, wheat 
(Triticum  aestivum L.) cv. Lakhish, pepper (Capsicum 
annuum L.) cv. Maor, and  potato (Solarium tuberosum 
L.). For this purpose, heat-sterilized sandy soil was 
placed in 750 ml containers, in which the plants were 
seeded. Two weeks after emergence of seedlings, sus- 
pensions of 250-300 free-living  stages  of R.  macrosumus 
were introduced into  the rhizosphere and  the plants were 
kept in a growth chamber at 25 zk 10. Eight weeks after 
inoculation, plants were carefully removed from the 
(1) Contribution  from  the  Agricultural  Research  Organization (ARO), The Volcani  Center,  Bet  Dagan,  Israel, No. 2159-E, 1987 
series. 
Revue Nématol., 11 (4) : 385-389 (1988) 385 
E. Cohn & M. Mor (Mordechai) 
containers, roots were fiied  and stained in boiling lacto- 
phenol-acid fuchsin solution, cleared in lactophenol, 
and scanned under a dissecting microscope for presence 
. of mature females. A host  plant was designated as one 
which supported  mature females with egg masses on its 
roots. 
For root histological studies, soybean plants were 
prepared, inoculated with R. macrosonms, and grown 
and maintained as described above. Five weeks after 
inoculation, plants were removed, nematode-infected 
segments were selected, fixed, sectioned and stained as 
described by Cohn  and Mordechai (1977), and exam- 
ined and photographed under a compound microscope. 
For scanning electron microscopy, roots with nematodes 
were fiied  in glutaraldehyde and post-fiied  and dehy- 
drated by standard techniques. They were mounted on 
stubs, coated with gold, and viewed and photographed 
with a Cambridge Stereoscan S-180 electron microscope 
at 15 KV. 
Table 1 
Measurements of immature  and  mature  females 
of a  population  of Rotylenchulus macrosomus (Rm) 
compared with R.  renifonnis (fi) 
Immature fendes  Mature fe?nules 
In = 11.) (n = 8) 
a 
b 
0.49 
(0.47-0.51) 
(24.5-29.5) 
26.8 
3.5 
(3-3.8) 
12.7 
(11.8-14.7) 
134.4 
14.6 
(11.5-18.2) 
19.7 
(18.2-21.1) 
(58.9-63.3) 
62.1 
(122-140.1) 
0.40 0.56 0.46 
(0.37-0.41) (0.52-0.59) (0.41-0.48) 
22.3 
(21.4-23.1) 
3.1 
15.5 
(13.9-16.4) 
98.7 
9.6 
18.8 
(2.9-3.9) 
(91-1 11) 
(6.7-17.3) 
(17.3-21.1) 
71 59.8  68.6 
(70-72.8)  (58-62)  (64-74) 
renifomzis population  for comparison. The average body 
length of the R. macrosomus specimens is evidently 
somewhat shorter than  that of the type  population (cf. 
Dasgupta, Raski & Sher, 1968), but the outstanding 
typical characters s h o w  in  the original description, viz., 
relatively high " O and " h " values - are  prominent 
also in this population. The mature female of R. 
macrosomus (Fig. 1) differs from  that of R. renifomzis in 
its 20 O/O greater body length, and 15 O/o more anteriorly 
situated vulva (Tab. 1). In addition, the body posture of 
the  mature female of R. macrosomus is more strongly 
curved and convoluted than  that of R. renifomis, its tail 
often crossing the neck - as opposed to the relatively 
straight, outstretched  form of R. renifomis (Fig. 2 A, C). 
Rm  Rr  Rm  Rr 
Fig. 1. Rotylenchzrlus  macrosomus. Adult  female. '
* According  to the formula proposed by Perry,  Darling  and Thorne 
(1959). 
** Hyaline  portion of tail  (Dasgupta,  Raski & Sher, 1968). 
Resuks and discussion - - - 
MORPHOLOGY 
Measurements of some diagnostic characters of im- 
mature females of R. macrosomus are presented in 
Table 1, along with those of individuals from a R. 
Furthermore,  the distal portion in  the tail is distinctly 
different in the two species : rounded with a short 
spike-like process in R. renifomzis, and slender with a 
more elongated finger-like projection in R. macrosomus 
( H g 2  B,D). Clearly, these two species are morphologi- 
cally distinct in all life stages, including the mature 
female. However, the similarity between R. macrosomus 
and R. borealis Loof & Oostenbrink, 1962 - already 
observed by Dasgupta, Raski and Sher (1968) - is 
further accentuated by Our data  on the  mature female 
of the former. In their general morphology - notably 
386 Revue Nématol., 11 (4) :. 385-389  (1988) 
The mature fenzale of Rotylenchulus  macrosomus 
the curved body shape and the tail terminus - as well borealis has been shown to present considerable varia- 
as in body length and the V value (cf. Loof & Oosten- bility in morphological and biometric characters of the 
brink, 1962), the mature females of the two species show migratory stages (Germani, 1978). 
a remarkable resemblance. It is also  noteworthy that R. 
A C 
B D 
Fig. 2. Rotylenchulus macrosomus :A, B, Adult  females. R. reniformis : C, D, Adult  females.  (A  and C comparison of body  postures, 
€3 and D comparison  of  posterior  ends  and  tail  termini.) 
HOST RANGE 
Besides  olive, hosts of the  nematode included tomato, 
snap bean, corn, soybean and  potato. Five plant species, 
namely,  Cotton, pepper, sorghum, wheat and Sour 
orange, were recorded as non-hosts. Evidently, there- 
fore, R. nzacrosomus differs also in its host preference 
from R. reniformis. This difference is particularly 
meaningful regarding Cotton, which is an important 
economic crop  in Israel and has recently been found  to 
be  severely damaged by high populations of R. renifor- 
mis  (Cohn & Mordechai, 1984). The general  similarity 
in host spectrum  between R. macrosomus and R. borealis 
(cf.  Vovlas & Inserra, 1982)  is  also conspicuous, and may 
serve  as another  indication of proximity between the two 
species. 
HISTOPATHOLOGY 
In general, the  feeding behavior  of R. yllacrosomus is 
similar to that of R. ren$ofomnis (Rebois, Madden & 
Eldridge, 1975), R. borealis (Vovlas & Inserra,  1982) and 
R. parvus (Vovlas, Cohn & Inserra, 1985) on various 
hosts; i.e., the  nematode  penetrates  the cortical tissue of 
the  root  and comes to rest in  the endodermis, where it 
creates a hypertrophied feeding ce11 (Fig. 3 B). A syn- 
cytium is formed by hypertrophy of pericyclic cells 
adjacent to the  feeding cell, with dense  granular cyto- 
plasm and enlarged nuclei within the cells, and clearly 
visible partial ce11 Wall breakdown in  the region close to 
the  nematode head (Fig. 3 C, D). A feeding tube within 
the enlarged feeding ce11  is also formed (Fig. 3 D), as has 
been observed in other Rotylenchulus species (Vovlas, 
Cohn & Inserra, 1985). Hence, R. macrosonzus induces 
a plant reaction resembling that resulting  from  feeding 
by the three aforementioned species of Rotylenchulus, 
but differing markedly from R. macrodoratus, which 
induces a single uninucleate  giant ce11 within the host 
tissue (Cohn & Mordechai, 1977). Therefore, in this 
respect, too, there is a clear similarity between R. 
nzacrosomus and R. borealis. It is thus possible that closer 
investigation of the morphological and biological charac- 
ters of these two type populations in  future studies may 
raise questions  regarding the validity  of their taxonomic 
separation. 
Revue Nématol., Il (4) : 385-389 (1988) 381 
E. Cohn Br M. Mor (Mordechail 
Fig. 3. Rotylenchulus  macrosomus : Parasitism  on  soybean. A : Adult  female  attached  to  root; B : Formation  of  endodermal  feeding 
cell (FC) by  the  nematode  (n)  in  early  feedmg  stage; C : Section  of  root  tissue  reaction  in  late  feeding  stage; D : Detail of syncytium 
in  pericycle  tissue,  showing ce11 Wall breakdown  in  region  near  the  nematode  head,  and  presence of feeding  tube (FT). 
The mature  female of Rotylenchulus  macrosomus 
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COHN, E. & MORDECHAI, M. (1977). Uninucleate giant cell 
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Revue Nématol., 11 (4) : 385-389  (1988) 389 


Morphology and parasitism of the mature female of Rotylenchulus macrosomus

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