Cadang-cadang is a disease caused by ''Coconut cadang-cadang viroid'' (CCCVd, ''Cocadviroid cadangi''), a lethal

viroid Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms (flowering plants), and most cause diseases, whose respective eco ...

of several palms including

coconut The coconut tree (''Cocos nucifera'') is a member of the palm tree family (biology), family (Arecaceae) and the only living species of the genus ''Cocos''. The term "coconut" (or the archaic "cocoanut") can refer to the whole coconut palm, ...

(''Cocos nucifera''), African oil palm (''

Elaeis guineensis ''Elaeis guineensis'' is a species of Arecaceae, palm commonly just called oil palm but also sometimes African oil palm or macaw-fat. The first Western world, Western person to describe it and bring back seeds was the French naturalist Michel Ad ...

''), anahaw ('' Saribus rotundifolius''), and buri ('' Corypha utan''). The name cadang-cadang comes from the word that means ''dying'' in Bicol. It was originally reported on San Miguel Island in the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

in 1927/1928. "By 1962, all but 100 of 250,000 palms on this island had died from the disease," indicating an

epidemic An epidemic (from Greek ἐπί ''epi'' "upon or above" and δῆμος ''demos'' "people") is the rapid spread of disease to a large number of hosts in a given population within a short period of time. For example, in meningococcal infection ...

. Every year one million coconut palms are killed by CCCVd and over 30 million coconut palms have been killed since Cadang-cadang was discovered. CCCVd directly affects the production of

copra Copra (from ; ; ; ) is the dried, white flesh of the coconut from which coconut oil is extracted. Traditionally, the coconuts are sun-dried, especially for export, before the oil, also known as copra oil, is pressed out. The oil extracted ...

, a raw material for

coconut oil Coconut oil (or coconut fat) is an edible oil derived from the kernels, meat, and milk of the coconut palm fruit. Coconut oil is a white solid fat below around , and a clear thin liquid oil at higher temperatures. Unrefined varieties have a disti ...

and

animal feed Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word ''feed'' more often refers to fodder. Animal feed is an important input ...

. Total losses of about 30 million palms and annual yield losses of about of copra have been attributed to Cadang-cadang disease in the Philippines.

Characteristics

Viroid Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms (flowering plants), and most cause diseases, whose respective eco ...

s are small, single-stranded

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

molecules, ranging from 246 to 375

nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

s long. Unlike

virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...

es, they do not code for protein coats but contain genes for autonomous replication. 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.Maramorosch, K. (1991). ''Viroids and Satellites: Molecular Parasites at the Frontier of Life''. Boston: CRC Press. . The sequence and structure prediction of CCCVd has been documented. There are four low-molecular-weight RNA species ( ccRNAs) found associated with cadang-cadang disease. Of the four, two are related with the early stage of the disease: ccRNA 1 fast and ccRNA 2 fast. After several years, two other species appear and predominate: ccRNA 1 slow and ccRNA 2 slow. Moreover, they share

sequence homology Sequence homology is the homology (biology), biological homology between DNA sequence, DNA, RNA sequence, RNA, or Protein primary structure, protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments ...

with other viroids. Conditions for a viroid to infect its host include wounds on the host or infected

pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

grain deposited into an

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the sporangium, megasporangium), ...

. Not all of the mentioned conditions pertain to cadang-cadang. Tinangaja disease is caused by coconut trinangaja viroid (CTiVd), which has 64% sequence homology with CCCVd. This disease has been found in

Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...

. Coconuts from Asia and the South Pacific have been found to have viroids with similar (homologous) nucleic acid sequences of CCCVd. The

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

icity of CTiVd is uncertain. Coconut cadang-cadang

, also known as CCCVd, is responsible for a lethal

disease A disease is a particular abnormal condition that adversely affects the structure or function (biology), function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical condi ...

plant first reported in the early 1930 in the

. CCCVd is the smallest known

and it is biologically distinct from other viroids; it consists of circular or lineal single-stranded

with a basic size of 246 or 247, it is thought it can be transmitted by

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

(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

symptom Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

s 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

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.

Molecular structure

CCCVd are small, circular, and single-stranded. They cannot replicate themselves, and therefore are completely dependent on a host. CCCVd have a sequence of 246

s, 44 of which are common with most viroids. CCCVd can add a

cytosine Cytosine () (symbol C or Cyt) is one of the four nucleotide bases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attac ...

residue in the 197 position and increase the size to 247 nucleotides. It is known that forms of CCCVd with 247 nucleotides cause severe symptoms. Their minimum size is 246, but they can produce forms from 287 to 301 nucleotides. In CCCVd, changes in molecular forms are related to the steps of the disease. There are four different RNAs found in CCCVd, two of them fast and the other two slow (the difference between fast and slow RNA is their mobilities in electrophoresis gel). In the early stages of the disease, RNA fast 1 and RNA fast 2 appear, while in the late stages RNA slow 1 and RNA slow 2 are detected.

Geographical distribution

The CCCVd is widely spread in

and it is mostly found in

Bicol Region The Bicol Region, designated as Region V, is an administrative region of the Philippines. It comprises six Provinces of the Philippines, provinces, four on the Bicol Peninsula (the luzon#Southeastern Luzon, southeastern end of Luzon): Albay, Ca ...

Masbate Masbate, officially the Province of Masbate (Masbateño language, Masbateño: ''Probinsya san Masbate''; ), is an island Provinces of the Philippines, province in the Philippines located near the midsection of the nation's archipelago. Its provi ...

Catanduanes Catanduanes (; ), officially the Province of Catanduanes (), is an island province located in the Bicol Region of Luzon in the Philippines. It is the 12th-largest island in the Philippines, and lies to the east of Camarines Sur, across the M ...

Samar Samar ( ) is the third-largest and seventh-most populous island in the Philippines, with a total population of 1,909,537 as of the 2020 census. It is located in the eastern Visayas, which are in the central Philippines. The island is divided in ...

and other smaller islands in the zone. It is known that the present northernmost boundary is at the latitude of

Manila Manila, officially the City of Manila, is the Capital of the Philippines, capital and second-most populous city of the Philippines after Quezon City, with a population of 1,846,513 people in 2020. Located on the eastern shore of Manila Bay on ...

and the southernmost at the latitude of

Homonhon Island Homonhon Island is an island in the Provinces of the Philippines, province of Eastern Samar, Philippines, on the east side of Leyte Gulf. The long island is part of the Guiuan, Eastern Samar, municipality of Guiuan, encompassing eight barangays: ...

. This fact is important due to the proximity of the disease to the major coconut and oil palm growing area of

Mindanao Mindanao ( ) is the List of islands of the Philippines, second-largest island in the Philippines, after Luzon, and List of islands by population, seventh-most populous island in the world. Located in the southern region of the archipelago, the ...

. An isolated focus of infection has been found on the

Solomon Islands Solomon Islands, also known simply as the Solomons,John Prados, ''Islands of Destiny'', Dutton Caliber, 2012, p,20 and passim is an island country consisting of six major islands and over 1000 smaller islands in Melanesia, part of Oceania, t ...

, in Oceania. The available data at the present suggests that the

epidemiology Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and Risk factor (epidemiology), determinants of health and disease conditions in a defined population, and application of this knowledge to prevent dise ...

of cadang-cadang viroid may not be spreading into any specific route.

Variants

, a similar viroid known as coconut tinangaja viroid (CTiVd) has been found that causes a similar disease named tinangaja disease. This viroid has 64% sequence homology with the cadang-cadang viroid. There are other related viroids with the CCCVd, which are found in

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

and the South Pacific. They have a high degree of homology but the pathogenicity is uncertain.

Transmission

The mode of natural inoculation of the viroid is unknown. There has been evidence that the transmission through pollen and seed can occur but they have a very low transmission rates: progenies of healthy palms pollinated with diseased pollen, exhibited disease symptoms 6 years after

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, ...

. CCCVd can spread through mechanical inoculation primarily through contaminated farm tools such as harvesting

scythe A scythe (, rhyming with ''writhe'') is an agriculture, agricultural hand-tool for mowing grass or Harvest, harvesting Crop, crops. It was historically used to cut down or reaping, reap edible grain, grains before they underwent the process of ...

s or

machete A machete (; ) is a broad blade used either as an agricultural implement similar to an axe, or in combat like a long-bladed knife. The blade is typically long and usually under thick. In the Spanish language, the word is possibly a dimin ...

s, due to the improper sanitary conditions.Zelazny, B., Randles, J. W., Boccardo, G., and Imperial J.S 1982. ''The viroid nature of the cadang-cadang disease of coconut palm''. Scientia Flipinas, 1979 The efficiency of the mechanical inoculation has been influenced by factors such as the age of the test plant and the mode of inoculation. Experimental transmission of the CCCVd using insects as

vector Vector most often refers to: * Euclidean vector, a quantity with a magnitude and a direction * Disease vector, an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematics a ...

has been unsuccessful although there are few evidences that the transmission of the viroid might be related to the wounds of coelopteran insects, but this has not been properly investigated. The natural hosts of cadang-cadang identified are '' Cocos nucifera'', '' Corypha utan'', ''

'' and '' Roystonea regia''. The experimental hosts are '' Adonidia merrillii'', ''

Areca catechu ''Areca catechu'' is a species of palm native to the Philippines cultivated for areca nuts. It was carried widely through the tropics by the Austronesian migrations and trade since at least 1500 BCE due to its use in betel nut chewing. ...

'', '' Caryota cumingii'', ''

Dypsis lutescens ''Chrysalidocarpus lutescens'', also known by its synonym ''Dypsis lutescens'' and as golden cane palm, areca palm, yellow palm, butterfly palm, or bamboo palm, is a species of flowering plant in the family (biology), family Arecaceae, native pl ...

'', '' Saribus rotundifolius'', ''

Phoenix dactylifera ''Phoenix dactylifera'', commonly known as the date palm, is a flowering-plant species in the palm family Arecaceae, cultivated for its edible sweet #Fruits, fruit called dates. The species is widely cultivated across North Africa, northern A ...

'', '' Ptychosperma macarthurii'' and '' Roystonea regia''.

Detection

The

diagnosis Diagnosis (: diagnoses) is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in a lot of different academic discipline, disciplines, with variations in the use of logic, analytics, and experience, to determine " ...

by symptoms is not reliable enough so it's better to do a molecular diagnosis based in test samples. Some of these methods (like Dot-blot hybridisation) allow the scientists to detect the viroid even six months before noticing the first symptoms. The first step is the purification to obtain the

nucleic acid Nucleic acids are large biomolecules that are crucial in all cells and viruses. They are composed of nucleotides, which are the monomer components: a pentose, 5-carbon sugar, a phosphate group and a nitrogenous base. The two main classes of nuclei ...

s of the plant cells. The leaves of the plant located four or more below the spare leaf are cut. Afterwards, they are blended ( homogenize) with

sodium sulfite Sodium sulfite (sodium sulphite) is the inorganic compound with the chemical formula Na2SO3. A white, water-soluble solid, it is used commercially as an antioxidant and preservative. It is also suitable for the softening of lignin in the pulping an ...

. Then the extract is filtered and clarified by

centrifugation Centrifugation is a mechanical process which involves the use of the centrifugal force to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed. The denser components of the mixture migrate ...

(10.000 g during 10 minutes). The next step is to add

polyethylene glycol Polyethylene glycol (PEG; ) is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine. PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular wei ...

(PEG). Finally, after nearly two hours of incubation at 4 °C, and after another

(at low speed) the

s can be extracted by

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

procedures, for example. When approximately 1 g of coconut tissue has been purified, the

electrophoresis Electrophoresis is the motion of charged dispersed particles or dissolved charged molecules relative to a fluid under the influence of a spatially uniform electric field. As a rule, these are zwitterions with a positive or negative net ch ...

method can be started, which will help to identify the viroid by its relative mobility. The CCCVd is analysed in one or two dimensional polyacrylamide gels with a silver stain. The viroid can also be detected by a more sensitive method called dot blot molecular hybridization. In this method CCCVd is amplified by the PCR (

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...

) and the clones of CCCVd are used as templates to synthesize a complementary

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

or RNA chain. 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 An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

film, then if CCCVd is present it will appear as a dark colour. This dark tonality only appears when nucleic acid hybridisation occurs.

Pharmacology and treatment

Coconut cadang-cadang disease has no treatment yet. However, chemotherapy with

antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

has been tried with tetracycline solutions; antibiotics failed trying to alter progress of the

since they had no significant effect on any of the studied parameters. When the treated

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s were at the early stage, tetracycline injections failed to prevent the progression of the palms to more advanced stages, nor did they affect significantly the mean number of spathes or nuts.

Penicillin Penicillins (P, PCN or PEN) are a group of beta-lactam antibiotic, β-lactam antibiotics originally obtained from ''Penicillium'' Mold (fungus), moulds, principally ''Penicillium chrysogenum, P. chrysogenum'' and ''Penicillium rubens, P. ru ...

treatment had no apparent improvement either. Control strategies are elimination of reservoir species, vector control, mild strain protection and breeding for host resistance. Eradication of diseased plants is usually performed to minimize spread but is of dubious efficacy due to the difficulties of early diagnosis as the virus

etiology Etiology (; alternatively spelled aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek word ''()'', meaning "giving a reason for" (). More completely, etiology is the study of the causes, origins ...

remains unknown and the one discovered are the three main stages in the disease development.

Easily confused pests

Coconut Cadang Cadang Viroid (CCCVd) can be confused with another viroid called Coconut Tinangaja Viroid (CTiVd). That is because both viroids have 64% of their sequence of nucleotides in common. They both affect coconut palm, and infected plants have similar symptoms: spots on the leaves reduced top, yellow palms and even death. There are few differences between both viroids in the effects caused on fruit: CTiVd causes small nuts, while CCCVd causes round and reduced nuts. Moreover, CTiVd has 254 nucleotides of length, while CCCVd has 246.

Symptoms

Symptoms of cadang-cadang develop slowly over 8 to 15 years making it difficult to diagnose at an early time.Agrios 2005, pages 822-823. There are three main “stages” of defined series of characteristics: early, medium, and late stages.Philippine Coconut Authority. ''Coconut Cadang-Cadang Disease Primer.'' Philippine Coconut Authority. PCA. Web. 23 Oct. 2011. . The first symptoms in the early stage develop within two to four years of infection. These symptoms include scarification of the coconuts which also become rounded. The leaves (fronds) display bright yellow spots. About two years later, during the medium stage,European and Mediterranean Plant Protection Organization, CABI. (2008). ''Coconut Cadang-cadang viroid'' ata file Retrieved from http://www.eppo.org/QUARANTINE/virus/Coconut_cadang_cadang_viroid/CCCVD0_ds.pdf the inflorescences become stunted and eventually killed, so no more coconuts are produced. Yellow spots are larger and in greater abundance to give the appearance of

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

. During the final stage, roughly 6 years after the first symptoms are recorded, the yellow/bronze fronds start to decrease in size and number. Finally, all the leaves coalesce, leaving just the trunk of the palm “standing like a telephone pole”. Palms under 10 years of age are rarely affected by cadang-cadang; the incidence of disease increases until about 40 years of age and then plateaus.Randles, J.W.; Imperial, J.S. (July 1984). Coconut cadang-cadang viroid. Retrieved from http://www.dpvweb.net/dpv/showadpv.php?dpvno=287 "No recovery has ever been observed, and the disease is always fatal". African oil palm has similar symptoms as coconut but also have orange spotting on palms.Coconut cadang-cadang viroid. (2008). aption under Cadang-cadang photo May 4, 2010 ''Coconut Cadang-cadang viroid: cocadviroid CCCVd''. Retrieved from http://www.invasive.org/browse/detail.cfm?imgnum=0656010 on 20 Now. 2011.

Environment

Geographical location

Philippines: Southern

Luzon Luzon ( , ) is the largest and most populous List of islands in the Philippines, island in the Philippines. Located in the northern portion of the List of islands of the Philippines, Philippine archipelago, it is the economic and political ce ...

, and other small islands. Tinangaja was found in

Mariana Islands The Mariana Islands ( ; ), also simply the Marianas, are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the northwestern Pacific Ocean, between the 12th and 21st pa ...

. Evidence shows that CCCVd is negatively correlated with

altitude Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum (geodesy), datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometr ...

Dispersal

The CCCVd viroid can be transmitted by

, seed, and mechanical transmission; it infects almost all parts of the host after flowering.

Insect vectors

No insect vector is known at this time, and rate of dispersal is not related to proximity of clusters.

Control

No definite control measures exist at the present. * Genetic resistance and

Vector control Vector control is any method to limit or eradicate the mammals, birds, insects or other arthropods (here collectively called " vectors") which transmit disease pathogens. The most frequent type of vector control is mosquito control using a varie ...

are not options because resistant/tolerant varieties have yet to be discovered, and there is no known vector of CCCVd. * Eradication is ineffective because of the long latent period between infection and appearance of symptoms, which is approximately 1 to 2 years. * Cross-protection is a possibility for the future. Cross infection means inoculating the coconut with a mild strain of the viroid to give the coconut tree some degree of protection from infection by the killer form. This is similar to

Edward Jenner Edward Jenner (17 May 1749 – 26 January 1823) was an English physician and scientist who pioneered the concept of vaccines and created the smallpox vaccine, the world's first vaccine. The terms ''vaccine'' and ''vaccination'' are derived f ...

's pioneering

smallpox vaccine The smallpox vaccine is used to prevent smallpox infection caused by the variola virus. It is the first vaccine to have been developed against a contagious disease. In 1796, British physician Edward Jenner demonstrated that an infection with th ...

. He used

cowpox Cowpox is an infectious disease caused by Cowpox virus (CPXV). It presents with large blisters in the skin, a fever and swollen glands, historically typically following contact with an infected cow, though in the last several decades more often ...

to confer induced immunity on humans. But in the case of Cadang-cadang, this is still under research.

References

External links

* Agrios, G. N. (2005). ''Plant Pathology'' pp. 822–823. (5th ed.). Burlington, MA: Elsevier Academic Press. * Coconut cadang-cadang viroid. (2008). aption under Cadang-cadang photo May 4, 2010 ''Coconut Cadang-cadang viroid: cocadviroid CCCVd''. Retrieved from http://www.invasive.org/browse/detail.cfm?imgnum=0656010 on 20 Now. 2011. * European and Mediterranean Plant Protection Organization, CABI. (2008). ''Coconut Cadang-cadang viroid'' ata file Retrieved from https://web.archive.org/web/20100713213014/http://www.eppo.org/QUARANTINE/virus/Coconut_cadang_cadang_viroid/CCCVD0_ds.pdf on 3 Nov. 2011. * Hanold, D.; Randles, J.W.. (1991a) ''Coconut cadang-cadang disease and its viroid agent.'' Plant Disease 75, 330-335. * Hanold, D.; Randles, J.W. (1991b) ''Detection of coconut cadang-cadang viroid-like sequences in oil and coconut palm and other monocotyledons in the South-west Pacific.'' Annals of Applied Biology 118, 139-151. * * * * Maramorosch, K. (1991). ''Viroids and Satellites'': ''Molecular Parasites at the Frontier of Life'' (127-139). Boston: CRC Press. * Philippine Coconut Authority. ''Coconut Cadang-Cadang Disease Primer.'' Philippine Coconut Authority. PCA. Web. 23 Oct. 2011. . * Randles, J.W.; Imperial, J.S. (1984) ''Coconut cadang-cadang viroid.'' CMI/AAB Descriptions of Plant Viruses No. 287. Association of Applied Biologists, Wellesbourne, UK. * Randles, J.W.; Imperial, J.S. (July 1984). Coconut cadang-cadang viroid. Retrieved from http://www.dpvweb.net/dpv/showadpv.php?dpvno=287 * Randles, J. W. (1987). ''Coconut Cadang-Cadang''. In Diener, T. O. (Eds.) ''The Viroids'' (265-277). New York: Plenum Press. * * {{Taxonbar, from=Q18974697, from2=Q5016237 Coconut palm diseases Viral plant pathogens and diseases Pests of oil palm Viroids ja:ココナッツカダンカダンウイロイド