OCCURANCE OF CYLINDROCLADIUM QUINQUESEPTATUM LEAF SPOT ON HEVEA BRASILIENSIS IN SRI LANKA

Cylindrocladium quinqueseptatum is a serious pathogen of tree crops in the tropics. It has been shown that rubber is also affected by this pathogen in Malaysia and China. This is the first report of the natural occurrence of Cylindrocladium quinqueseptatum on Hevea brasiliensis in Sri Lanka.

During the latter part of the year 2003, an unusual leaf spot disease similar to Cylindrocladium leaf spot symptoms described in Malaysia was observed from two year old rubber plants of the clone RRISL 206 at Baduraliya, Kalutara.Disease symptoms consisted of numerous raised chlorotic spots.These pin head size lesions were more prominent on mature leaves and at later stages they became purplish brown in colour (Fig. 1).In 2008, typical disease symptoms were noticed in two more rubber clones namely RRISL 210 and RRISL 217 grown in bud wood nurseries.__________________________________________ *Corresponding Author's email: dirrch@sltnet.lk

MATERIALS AND METHODS
Diseased specimens were collected from Baduraliya in Kaluthara district and the symptoms were studied.The causal organism was isolated from the leaves on to Czapek's Dox Agar (CDA).Pure cultures were obtained and consequently single spore isolations were done.The fungal isolate was sent to the Commonwealth Mycological Institute, UK for authentification.The pathogen was identified as Cylindrocladium quinqueseptatum Boedjin and Reitsma and the specimen culture was deposited in the International Mycological Institute (IMI) herbarium IMI 391089.Koch's postulates were proved using polybag plants of clone RRISL 206.The plants were inoculated using conidial suspensions 5 X 10 4 conidia / ml and incubated in moist chambers.Regular inspections were made for the appearance of disease symptoms.Isolations were made again from the resulting lesions on CDA.
Leaves from above clones of Hevea brasiliensis which are susceptible to C. quinqueseptatum were inoculated with 10µl drops of a conidial suspension containing 10 3 conidiospores ml -1 , obtained from pure culture.Inoculated leaves were maintained in moist chambers at room temperature under normal light and dark conditions, each treatment consisted of 6 replicate of leaves.Controls were inoculated with sterilized distilled water.

RESULTS
The inoculated leaves showed leaf spots leading to lesions, the typical symptom of Cylindrocladium leaf spots.C. quinqueseptatum was confirmed from the lesions on re -isolation.
Sterile filaments terminate in a narrowly clavate vesicle (Fig. 3b) (2.5-3.0)µm wide.Leaves inoculated with C. quinqueseptatum developed lesions three days after inoculation from which the fungus was successfully reisolated.

CONCLUSION
This is the first report of the occurrence of Cylindrocladium quinqueseptatum on Hevea brasiliensis in Sri Lanka, No other report of this nature has been recorded in Sri Lanka (Jayasinghe, 2001) execept that rubber has been shown to be a potential alternate host following artificial inoculations (Jayasinghe and Wijesundera, 1996).

Figure 1 .
Figure 1.Leaves of rubber plants from Sri Lanka naturally infected with C. quinqueseptatum.

Figure 2 .
Figure 2. C. quinqueseptatum colony obtained from H. brasiliensis grown on CDA and viewed from (a) above and (b) below.