Coconut Research Institute Repository

Perera, P.I.P.

Yakandawala, D.M.D.

Hocher, V.

Vendeil, J.L.

Weerakoon, L.K.

Variations among anthers and their orientation during in vitro culture for inducing androgenesis in coconut

Fernando, S.C.

Clonal propagation of coconut : prospectus and limitations

Asanka, J.R.K.

Prasangika, J.P.C.

Marikkar, J.M.N.

Jayasundera, J.M.M.A.

Production of dried pulverized kernel for virgin coconut oil extraction: Assessment on particle size distribution, drying curve pattern and quality characteristics

Wijesekera, H.T.R.

Perera, L.

Wickramananda, I.W.

Herath, I.

Meegahakumbura, M.K.

Fernando, W.B.S.

De silva, P.H.P.R.

Preliminary Investigation on Weligama Coconut Leaf Wilt 
Disease: A New Disease in Southern Sri Lanka 
H.T.R. Wijesekara*, L. Perera, I.R. Wickramananda, I. Herath, M.K. Meegahakumbura, 
W.B.S. Fernando and P.H.P.R. de Silva, 
Coconut Research Institute, Bandirippuwa Estate, Lunuwila 61150. 
* corresponding author, email: cpd@cri.lk 
ABSTRACT 
An unusual yellowing o f leaflets in coconut palms in the Galle, Hambantota and Matara districts in 
the Southern Province o f Sri Lanka was observed in late 2006. The symptoms associated with 
affected palms are flattening and downward bending of leaflets, yellowing o f lower fronds followed 
by drying o f leaflets starting from the margins. Symptoms resemble that o f Kerala wilt disease in 
India. This condition was first reported from Weligama in Matara district and, hence called the 
"Weligama Coconut Leaf Wilt Disease" (WCLWD). 
Analysis o f nutrients N, P, K, Ca and Mg in leaflets of affected and healthy palms revealed that, 
yellowing o f leaflets has no relationship with nutrients. DNA extracts of bud leaves subjected to 
Nested PCR with phytoplasma specific primer pair combinations R16F2n / R16R2 with rU3 / fU5 and 
R16mF2 / R 1 6 R 2 with fU5 /rU3 yielded an amplification o f 773 base pair product in 3 o f 24 palms 
tested. Sequencing o f the PCR product confirmed phytoplasma as the causative agent o f WCLWD. 
The sequence o f the WCLWD was compared with the phytoplasma sequences deposited in the 
NCBI database and WCLWD sequence was found to be 9 8 % similar to sugarcane grassy shoot 
phytoplasma and sugarcane white leaf phytoplasma. Apart from WCLWD, another fungal disease 
of coconut leaf rot disease was also observed in the same locations, sometimes in the same palm. 
This is the first report o f association o f phytoplasma in coconut disease in Sri Lanka. 
K e y w o r d s : Coconut phytoplasma, Weligam Coconut Leaf Wilt Disease (WCLWD) 
INTRODUCTION 
Coconut is an important plantation crop grown in 
many t ropical parts o f the wor ld . It p rovides 
considerable amount o f daily caloric requirement 
for the people o f these countr ies . In Sri Lanka 
coconut is grown widely in many parts o f the island, 
but large s c a l e p lan t ings are l oca t ed in areas 
border ing Ka lu ta ra , Kurunega la , and Put ta lam 
districts, which, is termed "the coconut triangle". 
Many medium scale plantations and several home 
garden level pa lms are found in the Southern 
Province o f Sri Lanka , especial ly , in the "Min i 
Coconut Triangle ," which is bordered by the towns 
Middeniya, Bel ia t ta and Ranna . 
Production o f coconut in Sri Lanka is hampered by 
many diseases, such as bud rot, stem bleeding, l e a f 
blight, and Ganoderma root and bole rot which, 
occur in small patches. In 2 0 0 6 , an unusual yellowing 
and f lacc id i ty in leaf le t s o f c o c o n u t pa lms in 
Weligama area in the Matara district was observed. 
Hence, the name "Wel igama Coconut L e a f Wilt 
Disease" ( W C L W D ) was given to this disease. The 
symptoms o f affected palms were similar to that 
o f root (wilt) disease in Kerala, India (Mathewkutty, 
1 9 9 8 ; Koshy et al, 2 0 0 1 ) . Apart from W C L W D , 
another disease, l e a f rot, which was first reported 
in late 1999 in Wel igama area was also observed 
both in some W C L W D affected palms and in some 
unaffected palms. 
Hence, different methods were used to identify the 
causative organism o f the W C L W D . 
336 
WELIGAMA COCONUT LEAF WILT DISEASE 
MATERIALS AND METHODS 
A br ie f survey was carried out to demarcate the 
boundary o f the affected area. The symptoms o f 
the a f f e c t e d p a l m s and t h e i r p r o g r e s s i v e 
deve lopment were recorded. C ros s sec t ions o f 
tiunks, roots and inflorescences were examined for 
any abnormalit ies. Oil content o f mature nuts and 
s u g a r c o n t e n t o f w a t e r o f t e n d e r nuts w e r e 
measured. L e a f nutrient content was analyzed to 
study ,the reason for yellowing o f fronds. D N A from 
tender leaflets was subjected to Nested P C R with 
p h y t o p l a s m a s p e c i f i c p r i m e r s to c o n f i r m the 
involvement o f phytoplasma in the disease. 
RESULTS AND DISCUSSION 
Disease Symptoms 
The earliest symptom o f the disease is the flattening 
and downward bending o f leaflets giving the frond 
a ribbed or f laccid appearance. Crowns o f such 
palms appear darker (F ig . l a ) . Th is symptom is 
first seen in the younger leaves and becomes more 
prominent when the fronds are fully opened. The 
degree o f f laccidity o f leaflets varies among the 
fronds in a s ing le pa lm, wh ich is not readi ly 
recognizable to an untrained eye. The most striking 
feature o f this disease is the intense yel lowing o f 
lower whorls o f fronds up to about the 1 2 t h frond 
(Fig . 1 b) . The yel lowing becomes more prominent 
af ter ' the rains. Occas iona l ly , ye l lowing o f mid 
whorls o f fronds is seen in some palms. In such 
cases , ye l lowing is restricted to about 6 - 8 fronds 
in the middle whorl. Subsequently, drying up o f the 
leaflets starts from the margins o f the affected 
fronds (Fig . 1 c ) . Dried up fronds hang on the crown 
for s o m e t i m e before fa l l ing. In s o m e severe ly 
affected palms, the fronds also curl downward 
giving a c lumsy appearance to the crown. T h e tips 
o f fronds b e c o m e twisted o r break and hang down 
in some palms (F ig . Id) . Unopened bud l ea f looses 
its rigidity and bends downward in severely affected 
palms. 
Necrosis in unopened inflorescences or immature 
nut fall, have not been observed in affected palms. 
With the reduction in the number o f fronds, the 
crown becomes smaller and trunk begins to taper. 
A s the d i s e a s e p r o g r e s s e s , f e m a l e f l o w e r 
p r o d u c t i o n d e c l i n e s and the p a l m b e c o m e s 
unproductive. 
High degree o f necrosis o f root tips was observed 
in moderately affected palms, while no young roots 
were observed in severe ly affected pa lms . T h e 
roots show intense branching followed by necrosis 
o f stelar region o f young white roots (Fig . 2a and 
2b) . 
Majori ty o f the W C L W D affected palms were in 
the bear ing s tage, whi le few were pre-bear ing. 
Palms o f any stage were found to be susceptible to 
the d i s e a s e , p a l m s o v e r 3 yea rs o f a g e m o s t 
commonly affected. Flaccidi ty o f leaflets is seen 
even in seedlings below 3 years o f age, where as 
yel lowing is always seen only in older palms. No 
other palm species in the area were observed with 
similar symptoms. 
There was no difference in the sugar content o f 
nut wa te r mode ra t e ly a f fec ted and apparent ly 
healthy palms from the same area. Nut water from 
both in W C L W D affected and apparently healthy 
pa lms had sugar con ten t o f 5 . 8 6 % and 5 . 5 9 % 
respectively, which is in the normal range. T h e 
kernel o f nuts from moderately affected palms were 
similar to that o f apparently healthy palms but the 
oil content was 7 . 4 % lower in nuts from moderately 
affected palms 
There was no necrosis or colour change or change 
in hardness in the trunk tissues o f affected palms. 
Prevalence of diseased palms 
Wel igama coconut l e a f wilt disease is currently 
p r e v a l e n t in D i v i s i o n a l S e c r e t a r i a t R e g i o n s 
Akuressa , Athura l iya , Dev inuwara , D i c k w e l l a , 
Hakmana , Kamburupi t iya , Ki r inda-Puhulwel la , 
M a l i m b o d a , M a t a r a , P i t abeddera , T h i h a g o d a , 
Wel igama and Welipit iya o f Matara district, Gal le 
and Habaraduwa in the Galle district and in Beliatta, 
O o k e w e l a , T a n g a l l e and W a l a s m u l l a in the 
337 
SECOND SYMPOSIUM ON PLANTATION CROP RESEARCH 
(a) Flaccidity (b) Yellowing 
(c) Drying of leaflets from margin (d) Breaking tips of fronds 
Fig. 1. Progressive development of symptoms in palms affected by Weligama Coconut Leaf Wilt 
Disease (WCLWD) 
(a) Necrosis in root tip area (b) Extensive branching 
Fig .2. Symptoms seen in root system of palms affected by WCLWD 
33 S 
WELIGAMA COCONUT LEAF WILT DISEASE 
Hamban to t a dis t r ic t in the Sou the rn P r o v i n c e 
(Fig . 3 ) . As the disease is confined to a limited area, 
it is reasonable to assume that the disease is o f 
fairly recent origin in Sri Lanka. T h e disease is 
prevalent in all types o f soils from coastal areas to 
s loppy lands. T h e affected pa lms are found in 
pockets , somet imes several ki lometers away from 
each other. T h e y are in smal l c lus te rs even in 
affected lands or scattered throughout. 
b lack and fall off, while partially affected leaflets 
with b l a c k i s h sh r ive l ed t ips , and fronds wi th 
completely rotten leaflets appear as blackish "fishing 
rods" (F ig . 4). T h e fungi responsible for the l ea f 
ro t d i s e a s e a re Ceratocystis paradoxa, 
Colletotrichum gloeosporioids and Fusarium 
solani (Fernando et al, 2002). Currently l e a f rot 
d i s ea se is found in all a reas w h e r e W C L W D 
prevails. Most o f the l ea f rot affected palms had 
, ~ V" Jji-iirtqi >s*r IMP*— —. V V"' — 
Fig. 3. Map of Sri Lanka showing Weligama coconut leaf wilt disease (WCLWD) affected areas 
in the Southern Province 
Leaf rot disease 
L e a f rot disease was also observed to be associated 
with some o f the W C L W D affected palms. T h e 
symptoms o f l e a f rot disease are produced by a 
fungal infec t ion in the unopened fronds. After 
opening o f affected fronds, the rotten portions turn 
(a) Rotten leaflets o f affected bud l e a f 
Fig. 4. Symptoms of Leaf rot disease in coconut 
flattened leaflets as in the case o f W C L W D but 
y e l l o w i n g and margina l nec ros i s cou ld not be 
observed as the part o f leaflets are already rotten. 
(b) Affected fronds o f adult palms 
339 
SECOND SYMPOSIUM ON PLANTATION CROP RESEARCH 
Detection Confirmation of causative agent of W C L W D 
Analysis o f leaflets from affected palms grown in 
fertilized lands revealed that, the yel lowing is not 
r e l a t e d to n u t r i e n t d e f i c i e n c y , p a r t i c u l a r l y , 
Magnes ium, Potassium and Calc ium (Table 1). 
S ince , the symptoms o f the W C L W D resemble that 
o f root (wil t ) disease in Kera la , India, which is 
claimed to be caused by a phytoplasma, studies were 
conduc ted to inves t iga te whe the r W C W L D is 
associated with a phytoplasma. 
Milky white to ivory coloured bud leaf samples were 
co l l ec t ed from mildly or modera te ly W C L W D 
affected palms and 10 g o f chopped ekel p ieces 
were used to extract D N A . Total D N A from bud 
leaves was extracted by C T A B method (Sambrook 
et al, 1 9 8 2 ) , and used for nes ted P C R wi th 
phytoplasma specific primer pairs R 1 6 F 2 n / R 1 6 R 2 
and fU5 / rU3 . Similarly, primer pair combinat ions 
R 1 6 m F 2 / R 1 6 m R l and f U 5 / rU3 were also used 
and a P C R product o f expected size o f 7 7 3 bp was 
obtained (F ig . 5 ) . P C R product was purified by 
Nutrient content 
Category N % K % M g % C a % 
Affected palms 2 .18 1.87 0 .34 0.43 
Healthy palms 2.21 1.78 0.27 0.33 
S D 0.281 0.691 0 .328 0 .144 
Suff iciency range 1 . 9 - 2 . 1 1 . 2 - 1 . 5 0 . 2 5 - 0 . 3 5 0 . 3 5 - 0 . 5 
(Mean of 9 palms) 
Table 1. Percent nutrient levels in leaflets from 14th frond in moderately WCLWD affected palms 
and appararently healthy palms 
M 
w S S S SR9 N6N7S S S S 
M - I kb ladder. H - healthy. W - water. S - sugarcane white leal phytoplasma. N 6 . N 7 . 
W C L W D palms. 
Fig. 5 . Agarose gel photograph of nested PCR products with phytoplasma specific primer pairs 
R16F2n / RI6R2 and fU5 / rU3. 
340 
WELIGAMA COCONUT LEAF WILT DISEASE 
"Wizard S V gel and P C R clean-up sys tem" kit 
(Promega, U S A ) and subjected to direct sequencing. 
The 'sequence was deposited in the N C B I data base 
(Access ion number: E U 6 3 5 5 0 3 ) . It showed 9 8 % 
sequence similarity with the sugarcane white l ea f 
and [sugarcane grassy shoot phytoplasmas. This is 
the first report o f a coconut disease associated with 
phytoplasma in Sri Lanka . 
P r e l i m i n a r y i n v e s t i g a t i o n s on the e f f e c t o f 
oxy t e t r acyc l i ne on the af fec ted pa lms showed 
remiss ion o f s y m p t o m s c o n f i r m i n g the above 
results. Several hypotheses have been postulated 
to explain the et iology o f the W C L W D . 
(1) i Disease has been introduced to the country 
f r o m s y m p t o m - l e s s o r n a m e n t a l p a l m 
imported to the country. 
( 2 ) . 1 Pathogen has expanded its host range from 
sugarcane to coconut 
(3) Pathogen has expanded its host range from 
• wild grasses to coconut 
Carefully planned experiments are necessary to test 
these hypotheses. 
The distribution pattern o f W C L W D affected palms 
suggests involvement o f air borne vector/s . 
It isi suspected that the disease is transmitted by 
the plant hopper Proutista moesta and the lace bug 
Stephanitis typica as they are the most c o m m o n 
sucking insects on coconut in Sri Lanka as in the 
case o f root wilt disease in India ( K o s h y et al., 
2 0 0 1 ) . 
design proper disease management strategies. A 
readily diagnostic P C R method through designing 
o f W C L W D phytoplasma specific primers for the 
P C R and identification o f best tissue type for the 
detection is currently underway. 
REFERENCES 
Fernando, L.C.P., Manoj, P., Perera, K.F.G. and Pemasiri, 
N.G. ( 2 0 0 2 ) . Proving pathogenicity o f fungi 
associated with leaf rot disease, pp. 161. In: 
Jayasekara, C , Somasiri, L.L.W., Henry Nimal 
Appuhamy, RA. and Idirisinghe, I.M.S.K. (Eds). 
Report of the Coconut Research Institute for 
2002. Coconut Research Institute o f Sri Lanka, 
Lunuwila. 
Koshy, P.K., Solomon, J . J . and Nair, C.P.R. (2001) . 
Diseases, pp. 3. In: Raju, C.R., Mohan, C , 
Maheshwarappa, H.P., Anithakumari, P. and 
Gopal, M. (Eds) . CPCRI Regional Station, 
Kayangulam at a glance. Central Plantation 
Crops Research Institute Regional Station, 
Kayangulam 690 533, Kerala, India. 
Mathewkutty, T.I. (1998) Strategies to combat root (wilt) 
disease in Kerala. Indian Coconut Journal, 29: 
95-98. 
Sambrook, J . , Fritsch, E . and Maniatis, T. ( 1 9 8 2 ) . 
Molecular cloning. A Laboratory Manual. Cold 
Spring Harbor Laboratory Press, Ny, U S A . 
Pp. 6 . 3 - 6 . 6 and 1 4 . 5 - 1 4 . 3 4 . 
FUTURE RESEARCH 
As the W C L W D was detected recently, hardly any 
information is available on its epidemiology, etiology, 
symptomatology, vec tors and al ternat ive hosts . 
T h e r e f o r e , fu ture r e s e a r c h a r e a i m e d at 
understanding on the above aspects and thereby to 
i 
341 


Preliminary investigation on Weligama coconut leaf wilt disease: A new disease in Southern Sri Lanka

Potential of activated coconut shell charcoal (ACSC) in vitro culture of Cocos nucifera L.(coconut)

Nainanayake, N.P.A.D.

Ranasinghe, C.S.

Tennakoon, A.T.

Effect of drip irrigation on canopy and soil temperature, leaf gas exchange, flowering and nut setting of mature coconut (Cocos nucifera L.)

Wijebandara, D.M.D.I.

Studies on influence of nutrient levels on yield of rice (oryza sativa L.) under system of rice intensification (SRI) and conventional methods of cultivation

Fernando, J.A.K.M.

Weerasinghe T.M.S.G.

Mallwaarachchi, S.M.

Jayasekera, C.

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Marikkar, J.M.M.N.

Jayasundara, J.M.M.A.

Kumari, A.G.O.

Waidyarathna, K.P.

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Senarathne, S.H.S.

Vermi-composting technology for sustainable farming systems in tropical coconut plantations

National Science Foundation of Sri Lanka

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