Miah, S.A.

Rahman, M.L.

Horizon / Pleins textes

Occurrence and distribution of white tip disease in 
deepwater rice areas in Bangladesh 
Mohammed Loothfar RAHMAN and  Siddique  Ali  MIAH 
Plant Pathology Division,  Bangladesh Rice Research Institute, Joydebpur, Gazipur,  Bangladesh. 
SUMMARY 
White-tip  disease of rice  caused  by the  nematode Aphelenchoides besseyi Christie,  1942  is  distributed  in  low to moderate  levels 
of infestation in most  of the deepwater  rice  areas in Bangladesh. The highest  disease  incidence  with  largest  nematode  population 
per  plant was  observed at the booting  or  flowering  stage  of the crop.  Approximately 25 O/O of  seed  samples  collected  from  farmers’ 
seed stores or from fields at harvest, were found to be infested with this nematode. About 73.5 O/O infested seed samples had 
5-25  nematodesllO0  grains.  Rajbowalia,  a  local  variety,  was found to  be  highly  susceptible  and  had  273 to 1 031 live  nematodes 
per 100 grains.  Diseased  panicles  were  significantly  shorter,  weighed  less,  had  fewer  filled  grains  and  lower 1 000-g ain  weight than 
apparently  healthy  panicles. 
B S U M É  
Présence et répartition de  la maladie du N white tip )) dans les zones de  culture du  riz inondé  du Bangladesh 
La maladie du white-tip N du riz causée par le nématode Aphelenchoides besseyi Christie, 1942 est répartie, avec des taux 
d‘infestation  faibles à modérés,  dans  la  plupart  des  zones  de culture du riz  inondé du Bangladesh. La plus  forte  incidence  de  la 
maladie  et  les  populations du nématode  les  plus  élevées  sont  observées  pendant  les  périodes  tallage et  de  floraison.  Environ 25 
des  échantillons  de  semences  prélevés  dans  les  greniers  des  paysans  ou  dans  les  champs, au moment  de  la  récolte,  sont  infestés 
par  le  nématode.  Environ 733 O/O des  échantillons  de  semences  contiennent 5 à 25 nématodes  pour  100  grains. La varitté locale 
Rajbowalia  est  la  plus  sensible  avec  273 à 1 031 nématodes  vivants  pour  100  grains.  Par  rapport  aux  panicules  saines  les  panicules 
infestées  sont  significativement  plus  courtes,  plus  légères,  contiennent  moins  de  grains  pleins  et  le  poids de 1 O00 grains  est  plus 
faible. 
White-tip disease of rice, caused by a seed borne 
nematode Aphelenchoides besseyi Christie, 1942, has 
been found in upland or irrigated rice in many rice 
growing  countries  in Asia, Tropical America, USSR  and 
Africa (Franklin & Siddiqi,  1972;  Fortuner & Williams, 
1975;  Ou, 1985). It has  caused variable yield losses in 
different  countries  ranging  from 14.5 to 46.7 9’0 in  Japan 
(Nishizawa & Yamamoto, 1951),  40-50 O/O in USA (At- 
kins & Todd, 1959),  29 to 46 O/o in  Taiwan  (Hung, 1959), 
41 to  71 O/O in  USSR (Tikhonova, 1966) and 20 to 60 O/o 
in India (Rao, Prasad & Panwar, 1985). Tamura and 
Kegasawa (1959) stated  that if al1 stems of a hi11 were 
infected,  the  maximum yield  loss would  be 60 O/O from 
a  susceptible variety in  Japan. 
In  Bangladesh  about 1.4 million  hectares of land  are 
devoted to deep-water rice which is broadcast  in 
March-April  and  harvested  in  November-December.  Its 
characteristic feature is an ability to elongate quickly 
under  submerged  conditions  and  an  upturning of pan- 
icles (kneeing) during recession of water. The associ- 
Revue Nématol. 12 (4) : 351-355 (1989) 
ation of A. besseyi with deep water rice was first  reported 
by Timm (1955) but he  did not describe the characteristic 
symptoms of the disease  nor the  extent of its distribution 
in  deepwater rice in Bangladesh.  Recently  its  occurrence 
in several deep  water rice areas has been  noted  (Rahman 
& McGeachie,  1982;  Rahman,  1982;  Rahman & Taylor, 
1983). 
Therefore  a survey of A. besseyi in Bangladesh was 
undertaken  and  its  symptoms  under field  conditions,  the 
extent of its  distribution  in some selected deepwater rice 
areas, the levels of infestation  in  the  farmers’  seed  stock 
and  its effects on yield components were investigated. 
Materials  and  methods 
SYMPTOMS AND POPULATION DYNAMICS 
Based on chlorotic discolouration of the leaf sheath 
just below the collar, 3 month-old seedlings of the 
35 1 
M. L. Rahman & S. A. Miah 
deepwater rice cv. Rajbowalia were selected and  marked 
by bamboo  stakes for recording  symptoms at  different 
growth stages. Three samples, each of 25 stems or 
panicles  showing  symptoms were taken at each growth 
stage, the  nematodes  extracted,  counted and their 
identity  confirmed microscopically. Percentage of plants 
showing  syrnptoms of the disease was estimated from 
20 x 1 m2 frame  counts  on each sampling day in  the 
same  field. 
INCIDENCE AND  DISTRIBUTION OF THE DISEASE 
Fifteen different deepwater rice areas were selected 
based on easy access but representative of typical  deep- 
water  rice  situations. Ten fields in each of these  selected 
areas were surveyed  randomly to record the  number of 
healthy  and  diseased  plants. The percentage of plants 
infested in each  field was calculated  using 20 x 1 m2 
frame  counts.  Infestations in farmers' seed stocks were 
also investigated at Manikganj, 80 km West of Dhaka : 
a  few days before sowing, 196 seed samples of eighteen 
deepwater  rice  varieties were collected, representing 
137 farmers  form  nine villages. Twenty seeds from each 
sample were  Split open  and soaked  overnight, the nema- 
todes extracted were examined and identified micros- 
copically. Based on the presence of nematodes, seed 
samples were indexed at different levels  of infestation. 
The infestation level'in the seed stocks (March/April) 
was compared with the actual infestation level in the 
field :, 127 fields were surveyed at harvest  (November- 
December)  when ten panicle  samples were taken from 
each field, the panicles  threshed and nematodes  ident'- 
ified and counted from twenty seeds. The index of 
infestation was estimated  as  before. 
EFFECTS ON YIELD COMPONENTS 
Ten apparently healthy panicles and ten panicles 
showing  white-tip  symptoms were collected from each 
of ten different  white-tip  infested  fields  planted  with cv.
Rajbowalia at Manikganj. Length  and weight of these 
panicles were recorded and  the panicles were threshed 
separately.  Filled and sterile  grains in each  panicle were 
counted  and  then  the grains of ten panicles were bulked 
from  each  field to obtain  the  1 O00 grain weight and also 
to estimate the  nematode  population  in 100 grains. 
Results 
SYMPTOMS  AND  POPULATION  DYNAMICS 
Chlorotic  discolouration in  an area 0.5 to 2.0 cm on 
the leaf sheath just below the collar of 3 month-old 
seedlings was found  to  be  the most  diagnostic symptom 
under  Bangladesh  conditions.  At the elongation stage, 
about a  2 to 5 cm length of the leaf tip of the affected 
plants  appeared  whitish. Also, chlorotic  stripes  along  one 
edge of the affected leaf were always noticed. At the 
352 
~ ~~~ 
booting stage, the flag leaf of the affected plant was 
characteristically  shortened,  twisted,  crinkled,  and  often 
distorted or Split longitudinally. Complete or partial 
emergence of panicles occurred on  infested plants  with 
whitish spikelets on  the  tip  or  throughout.  The affected 
spikelets were shrunken  and  unfilled. 
Examination of plants throughout  the growing season 
revealed that  the highest  nematode  population  occurred 
at  the booting  or  flowering  stage of the crop. The highest 
percentage of plant  infestation were also  observed at this 
stage.  Both  the  nematode  population  per  plant and  the 
infestation  percentage  increased from  the tillering  stage 
to  the booting  stage  and then declined at harvest  (Fig. 1). 
A B C D 
Fig. 1. Population dynamics of white tip nematode under 
different  stages of deepwater  rice  and  its  relation  with  disease 
severity (A : Seedling  stage; B : Tillering  stage; C : Flowering 
stage; D : Harvest). 
INCIDENCE AND  DISTRIBUTION 
The survey  indicated  that  most of the deepwater rice 
areas were infested  and that white-tip  disease is widely 
distributed in Bangladesh. Among the fifteen  areas 
examined (Fig. 21, ten areas were infested.  Among the 
461 fields examined, 112 fields (24.3 "O) were infest- 
ed. The severity of infestation in these fields was as 
follows : 88.4 O/O fields  had low infestations (1-5 O/O plants 
infested/m2), 11.6 O/o fields had moderate infestations 
(6-10 O/o plants  infested/m2), but  no fields  with  higher 
infestation levels  were recorded. 
Revue Nématol. 12 (4) : 351-355 (1989) 
W’hite-tip of rice in Bangladesh 
7 - 
O 5 0  K m  
Fig. 2. Distribution of Aphelenchoides besseyi in  selected 
deep-water  rice  areas of Bangladesh ( = sarnpling  places; 
district headquarters : 1 = Rajshahi; 2 = Tangail; 3 = Syl- 
het; 4 = Pabna; 5 = Manikganj; 6 = Dhaka; 7 = Comilla). 
From this  survey  Moishakhali,  Dubail,  and  Gozaria 
of Pabna,  Tangail  and  Manikganj  districts respectively 
were identified as the most important endemic areas for 
white-tip  disease. 
A  total of  25 O/o of the stored  seed  samples  and 22.8 O/o 
of the fresh seed samples examined were found  to  be 
infested with the white-tip nematode (Tab. 1). It was 
found  that  the cvs  Bowalia, Digha, Hijoldigha, Rajbowa- 
lia, Molladigha and  Dhepo, grown widely in Manikganj, 
were infested.  Although the  number of samples  taken of 
Rajbowalia were.low,  this  variety was found  to  be  the 
most  susceptible to white-tip  nematode  both in terms of 
infestation level and nematode numbers per 20 seeds 
(Tab. 1). It was also observed that  fresh seeds always had 
fewer nematodes than stored  seeds : a few samples  had 
more than 100 nematodes/20 seeds, most of the  samples 
having less than 20 nematodes/20 seeds. However, there 
were varietal  differences both  in infestation level and  in 
the  numbers of nematodes in seeds  (Tab. 1). 
EFFECT ON YIELD COMPONENTS 
The effects of A. besseyi on panicle yield in suscep- 
tible cv. Rajbowalia (Tab. 2) indicated that panicles 
Revue  Nématol. 12 (4) : 351-355 (1989) 
with white-tip symptoms were significantly shorter by 
30.43 O/O and lighter by 59.26 O/O than  the panicles without 
disease  symptoms. The diseased panicles had few filled 
grains and 69.5 % of grains were sterile. The weight of 
1 O00 grains from diseased panicles  decreased by 
65.44 % and  the  nematode  population  per 100 seeds in 
diseased  panicles (1  03 1)  was significantly  higher than  in 
panicles  without  apparent  disease  symptoms (273) 
(Tab. 2). 
Discussion 
Examination of deepwater rice plants at  the vegetative 
stage, panicles at harvest and seed samples from farmers’ 
store, indicated that  the white-tip nematode is widely 
distributed  in  the deepwater rice areas of Bangladesh. 
The symptoms  on leaves,  e.g. whitening of the leaf tip 
during  the vegetative stage, and  the shortened,  twisted 
and  crinkled  flag leaf seen during  the reproductive  stage 
of deepwater rice  were similar to  that reported in  other 
types of rice (Yoshii &Yamamoto,  1950; Todd & Atkins, 
1958; Muthukrishnan, Rajendran & Chandrasekaran, 
1974; Ou, 1985). The chlorotic stripes along one edge 
of the leaf  of an infested  deepwater rice plant was noted 
for  the  first time  as an important leaf symptom under 
Bangladesh  conditions. The presence of nematode  in- 
fested  grains  on the  uppermost  part of the panicle  or 
throughout the panicle, together with the apparently 
healthy  grains  are in accordance  with the  report  made 
for other types of rice (Steele, 1970). The cholorotic 
symptoms on the leaf are similar for both ufra and 
white-tip diseases but  the whitening  appears  on the  tip 
of the leaf for white-tip but  starts  at  the base of leaf 
sheath  for  ufra : in white-tip the  tip of the affected leaf 
becomes thin  and thread-like. 
The deepwater rice plants were less affected by A. 
besseyi during  the tillering  stage  before  flooding and  the 
number of nematodes  per  infested plant was also low, 
which  could  be due  to  the slow rate of nematode devel- 
opment and multiplication under pre-flooded condi- 
tions. The reasons  for the greater number of nematodes 
per  plant  and high  infestation levels  of plants during  the 
flowering stage of the crop (at receding flood levels, 
Sept.-Oct.) were not investigated but  it is possible that 
flood  water,  high  atmospheric  humidity and free  mois- 
ture on the leaf surface during flood  (JunelJuly- 
SeptJOct.)  might play an important role in spread and 
multiplication of the nematodes. Maximum  numbers of 
nematodes in grains at heading  stage was also  observed 
by Nandakumar et al. (1975). The apparent reduced 
infestation level at harvest  could  be due  to  the masking 
of symptoms on leaves as they  die and dry  out. 
Examination of both  the  stored  and  fresh  seed Sam- 
ples of deepwater  rice revealed that more than 20 O/O seed 
samples were infested with A. besseyi and contained 
10-615 nematodes  per 100 grains (Tab. 1). Fukano 
(1962) in Japan,  indicated  that  30  or  more live nema- 
353 
M.  L. Rahman & S. A. Miah 
todes per 100 grains may be the possible economic rice in  the Manikganj  area of Bangladesh, also with the 
threshold level in a susceptible cultivar. This w d d  susceptible cv. Rajbowalia (Tab. 1) in which a high level 
suggest that A. besseyi is causing yield loss of deepwater of grain  sterility was found  in diseased panicles. 
Table 1 
White-tip  nematode  infestation  in  farmers’  stored  seed 
and  in  fresh  seed  samples at harvest  in  Gozaria  beel  area,  Manikganj) 
Rice variety Nzmber of seed % infestation  Av rage numbers 
samples infested with A. besseyi of A. besseyi 
with A. besseyi per 20 seeds 
~ ~ 
Stored Fresh Stored Fresh Stored Fresh 
Bowalia 8 (46) 6 (43)  17.4  14.0  21  12 
Choto  bowalia 3 (6) 2 (6) 50.0 44.3  11  4 
Rajbowalia  2  (1)  6  (6)  100.0  100.0  123  18 
Digha  7  (21)  7  (35)  33.3  30.3 8 7 
Hijoldigha  15  (43) 3 (10)  34.9 33.3 25  6 
Jhuldigha 3 (9) j 2(10) 33.3  20.   7 4 
Molladigha  2  (26) 1(10) 7.7  10.0 103 8 
Manikdigha 0 (1) - 0.0 - O 
Dhepo 4  (26) 1 (4)  15.4  25.0  4 5 
Sarsari  1  (3) - 33.3 - 2 
Modhusail  2  (6) - 33.3 - 5 
Dudsail 0 (1) - 0.0 - O 
Morichful 2  (2) - 100.0 - 100 
Shamobhanga 0 (1) - 0.0 - O 
Kaika 1 (1) - 100.0 - 3 
Jainga  beez 0 (1) - 0.0 - O 
Holud  jaron 0 (1) - 0.0 - O 
Rapladhan 0 (1) - 0.0 - 0 
Boron - 0.0 O 
Upchaga 
- 
- 
- 
- 
- 
- 
- 
- 
- 
- 
- 0 (2) - - 1(1) - 100.0 - 15 
Figures within the  parenthesis  are total seed  samples. 
- samples were not collected. 
Table 2 
Population  density of  white-tip  nematode in rice  grains and its  influence 
on  yield  components  in  deepwater  rice, cv. Rajbowalia. 
Yield  component Plant Plants Percent of t - value 
without with increase (+) 
disease disease or  decrease 
symptoms symptoms (-1 
Panicle  length  (cm) * 
Panicle  weight  (g) * 
Filled  grain  (no.)/panicle * 
Sterile  grain  (no.)/panicle * 
1 O00 grain  weight (g) 
Nematodes/100  grains 
29.9 20.8 - 30.43 22.20** 
5.4  2.2 - 59.26 18.79** 
198.0  36.0 - 81.82 14.26** 
22.0  82.0 + 272.73 28.35** 
21.7  7.5 - 65.44 15.33** 
273.0 1031.0 + 277.66 5.06** 
** Significant  at P = 0.01 level by t - test. 
* Means of 10 samples. 
354 Revue Neinatol. 12 (4) : 351-355 (1989) 
White-tip of rice in  Bangladesh 
As A. besseyi is seed borne, the nematode is easily 
transmitted  from locality to locality. Under deepwater 
rice environments the nematodes could also be water 
dispersed from an infested field to a healthy field. 
Therefore  the results  suggest that seeds from infested 
areas should be treated before sowing to control and 
prevent further spread of the  nematode  in deepwater 
rice as is done  with  other  types of rice. 
ACKNOWLEDGEMENTS 
This work  was  carried out under  phase-1 of the ODA-BRRI 
Deepwater Rice Project and the authors acknowledge the 
assistance of the Overseas  Development  Administration of the 
Government of the  United  Kingdom. 
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Accepté pour publication le 17 décembre 1988. 
Revue Némzatol. 12 (4) : 351-355 (1989) 355 


Occurence and distribution of white tip disease in deepwater rice areas in Bangladesh

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