Coconut is an important tree crop of the coastal regions in India. Among the coconut producing countries India ranks first in production and productivity. All parts of the crop are useful and the coconut is associated with the social, cultural and economic life of Indian people. In spite of its hardiness, coconut is attacked by a variety of diseases such as basal stem rot, root wilt, stem bleeding, bud rot and leaf rot. The root wilt disease (RWD) is caused by a phytoplasma and in Kerala state alone RWD is responsible for an annual loss of 968 million nuts. The disease was endemic to Kerala state; but recent research has shown that the disease is spreading and is making an impact in the neighbouring state, Tamil Nadu. RWD is non-lethal, debilitating and slow spreading. The RWD affected palms become susceptible to attack by pests and diseases. Leaf rot disease (LRD) appears superimposed on RWD and there exists a close relationship between these two diseases. About 65 per cent of RWD affected palms are found to be also infected with LRD. There is a sharp deterioration in the canopy of the LRD affected palms and reduction in nut yield as the leaves /leaflets dry up, shrivel and fall off in the wind, resulting in decreased photosynthetic activity. The loss due to LRD was estimated at 461 million nuts per year. Economic control of LRD cannot be achieved by following the current recommendations. The reasons for this may be: 1) LRD is a disease superimposed on RWD 2) the involvement of more than one fungal pathogen and 3) the existence of variability within each fungal species.

                LRD is noticed in palms of all ages even in one-year-old field planted seedlings and all soil types. The rotting of emerging spear leaf is the first visible symptom. The initial symptoms appear as minute, water soaked lesions with brown /reddish brown margin and a bright halo at the centre. The lesions enlarge, coalescefreely especially on the sensitive, soft and tender leaflets of spear leaf resulting in extensive rolling in favorable weather conditions.

                 LRD is a disease resulting from infection by a complex of fungi; the important fungi associated with the disease are Collototrichum gloeosporioides, Exserohilum rostratum, Fusarium solani, F.moniliforme var. intermedium, Gliocladiutn vermoeseni, Cylindrocladium scoparium and Thielaviopsis paradoxa. Of the above fungi, C.gloeosporioides and E.rostratum are considered as the main pathogens of LRD. Earlier studies documented the pathogens associated with LRD, their in vitro interactions, sensitivity to chemicals and antagonistic microorganisms and seasonal fluctuations. The variation within each species and the detection of LRD pathogens at an early stage of the disease are necessary for effective LRD management.

                Advanced molecular techniques such as isozyme analysis, PCR. RFLP, probes, RAPD, and DNA sequencing are being successfully used to detect and characterize many plant pathogens, including fungi. These new techniques have been shown to be useful for investigating the relationship between different species, strains and varieties within species of fungi and for developing highly specific diagnostic tests. These pathogens were partially sequenced and submitted to EMBL. These sequence files were downloaded and maintained in Coconut Leaf rot Pathogens database. This database would provide

Database retrieval:-

• Select a sequence from the combo box and enter the name of the Pathogenes inside the text box.

• For 'Colletotrichum gloeosporioides' it is enough to type 'Colletotrichum' and for 'Exserohilum rostratum' type 'Exserohilum '.
• Publications on the above topics can be viewed by selecting 'Literature' from the combo.

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