Cadang-cadang facts for kids

Quick facts for kids Coconut cadang-cadang viroid
Virus classification
(unranked):	Virus
Phylum:	incertae sedis
Class:	incertae sedis
Order:	incertae sedis
Family:	Pospiviroidae
Genus:	Cocadviroid
Species:	Coconut cadang-cadang viroid

Cadang-cadang is a serious disease that kills palm trees. It is caused by something super tiny called the Coconut cadang-cadang viroid (CCCVd). This viroid mainly attacks coconut trees and African oil palms. The name "cadang-cadang" comes from a word in the Bicol language that means "dying."

The disease was first seen in the Philippines around 1927. It spread quickly, like an epidemic. For example, on San Miguel Island, almost all 250,000 coconut palms died by 1962. Every year, about one million coconut trees are killed by CCCVd. Since the disease was found, over 30 million coconut palms have died. This causes big problems for making copra, which is used for coconut oil and animal food. The Philippines has lost a lot of copra because of Cadang-cadang.

What is a Viroid?

Viroids are very small bits of RNA. They are much smaller than viruses. Unlike viruses, viroids do not have a protective outer coat made of protein. They also do not carry genes to make their own proteins.

Viroids can cause serious diseases in plants. But sometimes, they can also be "silent" and not show symptoms for a while. They usually infect plants through small cuts or wounds. They can also spread through pollen and seeds, but this happens less often.

The CCCVd is the smallest known pathogen (something that causes disease). It is made of a circular or straight piece of RNA. Once a coconut palm gets infected, its leaves start to show yellow spots. Then, the tree stops making nuts. It can take 8 to 16 years from when the first signs appear until the tree dies. Older trees are usually more affected.

How Does CCCVd Look?

CCCVd viroids are tiny, circular, and made of a single strand of RNA. They cannot make copies of themselves alone. They completely depend on a host plant to multiply.

Most CCCVd viroids have 246 nucleotides (the building blocks of RNA). Some forms can have 247 nucleotides. The forms with 247 nucleotides often cause more severe symptoms.

Scientists have found four different types of RNA in CCCVd. Two types appear early in the disease, and two other types appear later. These changes in the viroid's form are linked to how the disease progresses.

Where is Cadang-cadang Found?

The CCCVd viroid is mostly found in the Philippines. It is common in areas like the Bicol Region, Masbate, Catanduanes, and Samar. It has also been found on the Solomon Islands in Oceania.

Scientists are still studying how the disease spreads across different areas.

Similar Viroids

In Guam, there is a similar viroid called coconut tinangaja viroid (CTiVd). It causes a disease called tinangaja disease. This viroid is quite similar to CCCVd, sharing 64% of its genetic code.

Other related viroids have been found in Asia and the South Pacific. They are similar to CCCVd, but it is not clear if they cause disease.

How Does it Spread?

Scientists are not completely sure how the viroid spreads naturally. However, there is some proof that it can spread through pollen and seeds. But this happens at a very low rate. For example, healthy palms pollinated with diseased pollen showed symptoms six years later.

CCCVd can also spread through tools used on farms. This happens if tools like scythes or machetes are not cleaned properly after being used on an infected tree. The age of the plant and how the tools are used can affect how easily the disease spreads this way.

Scientists have tried to spread CCCVd using insects, but they have not been successful. There is a small amount of evidence that insect wounds might play a role, but more research is needed.

The main plants that get Cadang-cadang naturally are the coconut, Corypha utan, Elaeis guineensis (African oil palm), and Roystonea regia (royal palm).

How to Detect Cadang-cadang

It is hard to tell if a tree has Cadang-cadang just by looking at its symptoms. So, scientists use special tests to find the viroid. These tests can even detect the viroid up to six months before any symptoms appear.

One method is called electrophoresis. This helps identify the viroid by how it moves in a special gel. Another very sensitive method is called dot blot molecular hybridization. This method uses DNA or RNA pieces that glow or are radioactively labelled. If the CCCVd is in the sample, it will show up as a dark spot on an x-ray film.

Treatment and Control

Sadly, there is no cure for Coconut cadang-cadang disease yet. Scientists have tried using antibiotics like tetracycline and penicillin, but they did not stop the disease from getting worse.

To control the spread, people often remove diseased plants. However, this is difficult because it takes a long time for symptoms to show up after a tree is infected.

Scientists are also looking into other ways to fight the disease:

• Resistant Plants: They are trying to find or create coconut trees that can resist the disease.
• Vector Control: Since no insect that spreads the disease is known, this method is not currently possible.
• Cross-protection: This idea is like a vaccine for plants. It means infecting a coconut tree with a very mild version of the viroid. The hope is that this mild infection would protect the tree from the deadly form. This is still being researched.

What Can Cadang-cadang Be Confused With?

Coconut Cadang-cadang Viroid (CCCVd) can be confused with Coconut Tinangaja Viroid (CTiVd). This is because they share 64% of their genetic code. Both viroids affect coconut palms and cause similar symptoms. These include spots on the leaves, smaller tops, yellow palms, and eventually death.

However, there are a few differences in how they affect the fruit. CTiVd causes small nuts, while CCCVd causes nuts that are round and smaller than usual. Also, CTiVd is 254 nucleotides long, while CCCVd is 246 nucleotides long.

Symptoms of the Disease

The symptoms of Cadang-cadang appear slowly, over 8 to 15 years. This makes it hard to find the disease early. There are three main stages: early, medium, and late.

• Early Stage: This happens about two to four years after infection. The coconuts get scars and become rounder. The leaves start to show bright yellow spots.
• Medium Stage: About two years later, the flowers become stunted and die, so no more coconuts are produced. The yellow spots on the leaves get bigger and more numerous, making the leaves look yellow overall.
• Late Stage: Roughly six years after the first symptoms, the yellow/bronze leaves start to shrink and fewer of them remain. Eventually, all the leaves die, leaving only the trunk of the palm standing.

Young palms (under 10 years old) rarely get Cadang-cadang. The disease becomes more common as trees get older, up to about 40 years. Once a palm is infected, it never recovers and the disease is always fatal. African oil palms show similar symptoms, but they also get orange spots on their leaves.

Environment and Spread

Where it is Found

In the Philippines, Cadang-cadang is found in Southern Luzon, Samar, Masbate, and other small islands. Tinangaja disease, caused by a similar viroid, was found in Guam on the Mariana Islands. Studies show that CCCVd is less common at higher altitudes.

How it Spreads

The CCCVd viroid can spread through pollen, seeds, and by tools. It infects almost all parts of the host plant after it starts flowering.

Insect Carriers

Currently, no insect is known to carry and spread the CCCVd viroid. The way the disease spreads does not seem to be related to how close infected trees are to healthy ones.

ja:ココナッツカダンカダンウイロイド