Khan, F.A.

Horizon / Pleins textes

Hatching response of Rotylenchulus renijiormis 
to root leachates of certain hosts and nonhosts 
Fasahat A. KHAN 
Department of Crop Protection, Institute for Agricultural Research, Ahmadu Bello University,  Zaria,  Nigeria. 
Root  leachates  of  favourable  hosts such as  okra,  tomato,  castor,  egg-plant  and  cowpea  stimulated the  hatching of R. renifomzis 
larvae,  while  those  of  nonhosts  such  as  onion  and  chilli  suppressed  it.  Optimal  hatch  was  achieved  within  nine  hours  and further 
increase in duration of  leach  decreased it.  Leachates  obtained  from  five  seedlings  showed  optimal  hatching  activity  which  decreased 
with further increase  in  seedling  concentration. This was further confirmed  by tests  made  by diluting  the leachates  obtained  from 
the  roots of fifteen  seedlings. 
RÉSUME 
Eclosion de Rotylenchulus  reniformis en réponse aux exsudats radiculaires de plantes hôtes  et non hôtes 
Les  exsudats  radiculaires  provenant  d’une  part  de  dix  plantes  hôtes  (gombo,  tomate,  ricin,  aubergine,  haricot,  chou,  concombre, 
pois d’hgole, calebassier et blé) et  d’autre part de  cinq  plantes  non  hôtes  (oignon,  fenouil,  navet,  piment,  épinard)  ont  été  testés 
pour  leur  effet  sur  l’éclosion  des  larves  de R. renifomzis. Il  a  été  constaté  que l’éclosion était stimulée, à des  degrés  divers,  par  les 
exsudats du gombo,  de  la  tomate,  du  ricin,  de  l’aubergine et du haricot et  était  inhibée  par  ceux  provenant du piment  et de  l’oignon. 
L‘éclosion optimale a été obtenue avec des exsudats provenant de racines immergées pendant neuf heures;  cette éclosion est 
diminuée  si  la  durée  d’immersion  augmente.  Les  exsudats  provenant  de  cinq  jeunes  plants  de  tomate  ont  montré  une  action  optimale 
sur l’éclosion;  cette  action  diminue  si  le  nombre  de  ces  plants  est  augmenté.  Ce  phénomene  a  été  confirmé  par  des  tests  de  dilution 
d’exsudats  radiculaires  provenant  de  quinze  jeunes  plants‘  de  tomate. 
Larval hatching in plant parasitic nematodes is af- 
fected by various physical, chemical and seasonal fac- 
tors. Among  the chemical factors, root exudates from 
the  host plants have been  found to influence  hatching 
in various species of Heterodera (Baunacke, 1922; Fen-. 
wick, 1949; Winslow, 1955; Winslow & Ludwig, 1957; 
Doncaster, 1957) and Meloidogyne (Loewenberg et  al., 
1960; Jones & Nirula, 1963; Ahmad & Khan, 1964; 
Hamlen & Bloom, 1968; Webber & Barker, 1968). 
However, there  are  no  such  reports  outside  the family 
Heteroderidae.  Attempts were, therefore, made  to study 
the effect of : (i) root leachates from certain host and 
nonhost plants, (ii) duration of leach, and (iii) seedling 
concentration on larval hatching in  the reniform  nema- 
tode, Rotylenchulus renifomzis Linford & Oliveira, 1940. 
Materials and methods 
Ten host plants viz., okra (Abelmoschus esculentus 
Moench), tomato (Lycopersicon lycopersicuwz (L.) 
Karst.), castor (Ricinus communis L.), egg-plant (Sola- 
num melongena L.), cowpea (Vigna unguiculata L.), 
cabbage (Bmssica oleracea L. var. capitata), cucumber cu- 
cumis sativus L.), Bonavist bean (Uolichos lablab L.), 
bottle gourd (Lagenan’a  leucantha (Duch.)  Rusby) and 
Revue Nématol., 8 (4) : 391-393 (1985) 
wheat (Triticum aestivum L.) and five nonhost plants 
viz., onion (Allium cepa L.), di11 (Anethum graveolens 
L.), turnip (Brassica rapa L.), chilli (Capsicumhtescens 
L.) and spinach (Spinacia oleracea L.) were selected for 
these studies. Root leachates were prepared by immers- 
ing the excised roots of five, six day-old seedlings, 
grown in sterilized quartz sand in Petri plates in 10 ml 
of distilled water for six hours. For studying the effect 
of duration of leach on its potency, thoroughly washed 
excised roots of 50 six day-old tomato seedlings were 
immersed in 100 ml of distilled water and  samplesof 
leachates were taken  at 1, 3, 6, 9, 12, 15 and .18 hours 
intervals. Effect of seedling concentration on leachate 
potency was studied by immersing 1, 3, 5,  7, 9, 11, 13 
and  15 excised roots of tomato seedlings of the same  age 
in 10 , m l  of distilled water respectively. The leachate 
obtained  from  fifteen excised roots of tomato was 
termed “ x and different dilutions viz., 42, 43, 45, dl0 
and x/50 were prepared  from  it  to  study their  effect on 
leachate potency. Throughout  the studies five surface 
sterilized egg masses of R. renifonnis, obtained from 
pure culture, were transferred to 10 ml of aliquot 
contained in 5 cm Petri plates. An equal amount of 
distilled water with an equal number of egg masses 
transferred to  it served as control. Replication in each 
test was five fold. The plates were incubated  for a  week 
391. 
E A. Khan 
Table 1 
Larval  hatching  in  root  leachates of certain  host  and  nonhost  plants  after  one week  exposure. 
Cumulative larval 
hatch 
F 
S.D. 2.702  35351.140  08 7 0.894 1.414  .30   1.871  0. 94  1.517  2.608  1. 24  2.0  .817 . 0 .894 
113  145  162  116  103  70  59  65  72  73  19  64  62  28  67 68 
4.000*  10.240*  17.454*  .551*  2.420*  .008  0.160  .178  0.032  0.050  4.743*  0.032  0.071  3.160*  .002 - 
* Significant at 0.01 level (P < 0.01) 
at  room  temperature (30' k 1') after which the larval 
hatch was counted. 
Results  and discussion 
Results  presented in  Table 1 show that  root  leachates 
of five out of the ten host plants tested, tended to 
stimulate the  hatching of R. renifomzis larvae in varying 
degrees. Cumulative larval hatch in root leachates of 
okra, tomato,  castor,  egg-plant and cowpea, one week 
after  introduction, was 113, 145,  162,  116 and  103 
respectively as against  68 in water. Leachates  from the 
roots of remaining  host  plants viz., cabbage, cucumber, 
Bonavist  bean, bottle  gourd  and wheat had no obvious 
effect.  Leachates from  the roots of three out of the five 
nonhost plants viz., dill, turnip and spinach had no 
significant  effect on  the larval hatch, while onion and 
chilli evidently suppressed  hatching activity. 
Duration of leach  significantly  affected  the  leachate 
potency  (Tab. 2). The hatching activity increased with 
the increase in  duration of leach up to nine  hours, where 
optimal  hatching  occurred. Further increase in  duration 
brought about decrease in hatching. The number of 
larvae that hatched in leachates collected after fifteen 
and  eighteen  hours was  lower than  the hatch in water. 
The hatching  activity  increased  with the increase in 
seedling  concentration  (Tab. 3). The highest hatch 
occurred when roots of five seedlings were used for 
production of leachates. Further increase in  the  number 
of seedlings resulted in decline of hatch till it  reached  its 
lowest in leachates  prepared from  the roots of fifteen 
seedlings. Cumulative larval hatch  in  such leachates was 
lower than  in water. 
Similar  results  were  obtained  with six different  con- 
centrations of leachates prepared from the roots of 
fifteen tomato seedlings (hereafter termed as " x 
(Tab. 4). Evidently, the hatching activity increased with 
the increasing  concentration  reaching  its  highest in  x/3 
and  dropping  to  lower  than  in  water at x concentration. 
The concentration of x/3  corresponds to leachates pre- 
pared  from the roots of five seedlings (x = 15; x/3 = 5). 
392 
Table 2 
Larval  hatching in root  leachates of  tomato, 
collected  after  different  durations  of  leach. 
Duration  Cumulative F S. D. 
larval .hatch 
l h r  94  9.984*  0.56
3hr 117  30.296* 1 .O4 
6 hr' 146  71.574* 0.96 
9hr 167  112.374* 1 .O4 
12 hr 76  1.756 0.16 
15 hr 57  0.374 1.04 
18 hr 49  2.036 0.56 
Water 63 - 3.44 
* Significant at 0.01 level (P < 0.01) 
Table 3 
Larval  hatching  in  root  leachates  obtained from 
Different  concentrations of  tomato  seedlings. 
Seedling  Cumulative F S. D. 
concentration lama1 hatch 
1 53 0.003  1.44 
3 88 11.325*  1.84 
5 142 68.510*  0.64 
7 107 25.943*  0.64 
9 78 6.031* 1 .O4 
11 72  3.648*  1.04 
13 63  1.191  3.44 
15 43  0.529  0.24
Water 51 - 0.56 
* Significant at 0.01 level (P < 0.01) 
The results show that  hatching in  the reniform  nema- 
tode, R. renifonnis, was stimulated by root diffusates 
produced by certain  host  plants  and  suppressed by those 
produced' by certain nonhost plants. Apparently the 
Revue Nérnatol., 8 (4) : 391-393 (1985) 
Hatching response of Rotylenchulus  reniformis to root leachates 
Table 4 
Larval hatching  in  different  concentrations of 
root  leachates  obtained  from 
fïfteen  tomato  seedlings. 
Concentration Cumulative F S. D. 
of leachate larval  hatch 
450 37 0.028  1.04 
XI10 41 0.71 1 0.56 
xI5 54 9.215*  0.56 
XI3 61 17.776* 
d 2  
0.16 
46  2.844  0.16 
X 27  2.304  0.24 
Water 36 - 0.56 
* Significant at 0.01 level (P < 0.01) 
hatching  stimulants were certain  water  soluble  chemical 
substances.  Leachates  with  highest  potency were produ- 
ced  by castor  roots followed by tomato, egg-plant, okra 
and c o w p e a . i n h t  order. Duration of leach also .ha'd a 
marked  effect  on the leachate  potency. The decrease in 
rate of hatching  after  nine  hours  might have been the 
result of a fa11 in leaching due  to diminished reserves of 
these  chemical  substances  within the roots. It could  also 
be  due  to a degradation of the leachate or a reabsorption 
by the roots. The leachate potency was found to be 
directly proportional to seedling  concentration up  to  an 
optimum above which hatching was depressed. It is 
possible that the inhibitory effects observed at higher 
concentrations  were due  to  an osmotic  pressure  effect 
exerted by dissolved salts. It is also likely that the 
hatching factors, if present beyond a certain threshold, 
bring  about a reduction in hatching.  These  findings  are 
generally in agreement  with  those of  Winslow and 
Ludwig (1957) for beet  leachings  and Hague (1958) for 
potato  root  diffusates. 
REFERENCES 
AH-, A. & KHAN, A. M. (1964). Factors  influencing  larval 
hatching  in  the  root  knot  nematode, Meloidogyne incognita 
Accepté pour publication le 3 août 1985. 
(Kofoid & White, 1919) Chitwood, 1949. II. Effect of root 
leachates and certain chemicals. Indian Phytopath., 17 : 
102-109. 
BAUNACKE, W. (1922). Untersuchungen ZUT Biologie und 
Bekaempfung  des  Rueben-nematoden, Heterodera schachtii 
Schmidt. Arb. biol. Reichanst. Land u. Forstwirtsch., 11 : 
185-288. 
DONCASTER, C.  C. (1957). Growth,  invasion  and  root  diffusate 
production  in  tomato  and  black  nightshade  inoculated  with 
potato  root  eelworm. Nematologica, 2 : 7-15. 
FENWICK, D. W. (1949). Investigations on the emergence of 
larvae from cysts of the potato-root eelworm, Heterodera 
rostochiensis. 1. Technique  and  variability. J. Helminth., 23 : 
157-170. 
HAGUE, N. G. (1958). The concentration  of  potato  root 
diffusate  under  reduced  pressure. Nematologica, 3 : 
149-153. 
HAMLEN, R. A. & BLOOM, J. R. (1968). The hatching  response 
of Meloidogyne incognita eggs as affected by amino and 
nonamino  acid  fractions of root  exudates. Phytopathology, 
58 : 515-518. 
JONES, F. G. W. & NIRULA, K. K. (1963). Hatching  tests  and 
counts  of  primary  galls in assessrnent of nematicides  against 
Meloidogyne spp. Pl. Pathol., 12 : 148-154. 
LOEWENBERG, J. B., SULLIVAN, T. & SCHUSTER, M. L. (1960). 
The effect of pH and  minerals  on the  hatching  and  survival 
of Meloidogyne  incognita larvae. Phytopathology, 50 : 
215-217. 
WEBBER, A. J. & BARKER, K. R. (1968). Hatching  response  of 
Hypsoperine ottersoni to canarygrass  root  emanations. Proc. 
hebninth. Soc. Wmh., 35 : 34-37. 
WINSLOW, R. D. (1955). The hatching response of some 
root-eelworms  of  the  genus Heterodera. Ann. appl. Biol., 43 : 
19-36. 
WINSLOW, R. D. & LUDWIG, R.A. (1957). Studies  on  hatching 
stimulation in the beet nematode, Heterodera schachtii 
Schmidt. Canad. J. Bot., 35 : 619-634. 
Revue Nématol., 8 (4) : 391-393  (1985) 393 


Hatching response of Rotylenchulus reniformis to root leachates of certain hosts and nonhosts

Abstract

Similar works

Full text

Available Versions

Horizon / Pleins textes