Cadang-cadang is a disease caused by Coconut cadang-cadang viroid (CCCVd, Cocadviroid cadangi), a lethal viroid of several palms including coconut (Cocos nucifera), African oil palm (Elaeis guineensis), anahaw (Saribus rotundifolius), and buri (Corypha utan).
CCCVd directly affects the production of copra, a raw material for coconut oil and animal feed.
With abilities to cause serious disease, they are more commonly found in a latent stage, and their mode of infection is mainly mechanical, though documented cases exist of vertical transmission through pollen and seed.
Tinangaja disease is caused by coconut trinangaja viroid (CTiVd), which has 64% sequence homology with CCCVd.
Coconuts from Asia and the South Pacific have been found to have viroids with similar (homologous) nucleic acid sequences of CCCVd.
CCCVd is the smallest known pathogen and it is biologically distinct from other viroids; it consists of circular or lineal single-stranded RNA with a basic size of 246 or 247, it is thought it can be transmitted by seed or pollen (with low transmission rates) and occur in almost all plant parts.
Once infected, coconut palm shows yellow leaf spots and nut production ceases; from appearance of first symptoms to tree death, time ranges from around 8 to 16 years, but the pest is generally greater in older plants.
It is estimated that over 30 million coconut palms have been killed by cadang-cadang since it was first recognised and the loss of production is valued at about $80 – $100 for each planting site occupied by an infected tree.
[5] The CCCVd is widely spread in Philippines and it is mostly found in Bicol Region, Masbate, Catanduanes, Samar and other smaller islands in the zone.
This fact is important due to the proximity of the disease to the major coconut and oil palm growing area of Mindanao.
[13] CCCVd can spread through mechanical inoculation primarily through contaminated farm tools such as harvesting scythes or machetes, due to the improper sanitary conditions.
[14] The natural hosts of cadang-cadang identified are Cocos nucifera, Corypha utan, Elaeis guineensis and Roystonea regia.
The experimental hosts are Adonidia merrillii, Areca catechu, Caryota cumingii, Dypsis lutescens, Saribus rotundifolius, Phoenix dactylifera, Ptychosperma macarthurii and Roystonea regia.
Finally, after nearly two hours of incubation at 4 °C, and after another centrifugation (at low speed) the nucleic acids can be extracted by chloroform procedures, for example.
When approximately 1 g of coconut tissue has been purified, the electrophoresis method can be started, which will help to identify the viroid by its relative mobility.
These sequences are radioactively labelled so when they are put over the samples with the intention to analyse (on a supporting membrane) and exposed to x-ray film, then if CCCVd is present it will appear as a dark colour.
During the final stage, roughly 6 years after the first symptoms are recorded, the yellow/bronze fronds start to decrease in size and number.
[3] The CCCVd viroid can be transmitted by pollen, seed, and mechanical transmission; it infects almost all parts of the host after flowering.