Sandalwood (''

Santalum album ''Santalum album'', or Indian sandalwood, is a small tropical tree, and the traditional source of sandalwood oil. It is native to southern India and Southeast Asia. It is considered sacred in some religions like Hinduism, and some cultures plac ...

''. L), a semi-root

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

is the source of the East Indian

sandalwood Sandalwood is a class of woods from trees in the genus ''Santalum''. The woods are heavy, yellow, and fine-grained, and, unlike many other aromatic woods, they retain their fragrance for decades. Sandalwood oil is extracted from the woods for us ...

and

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

. Spike disease caused by

phytoplasma Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-lik ...

is the major

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

. The disease is noticed in all major sandal-growing states of

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

. Spike disease is characterized by extreme reduction in leaf size accompanied by stiffening and reduction of internode length. In advanced stage, the entire shoot gives the appearance of a spike inflorescence. Spiked trees die within 1–2 years after the appearance of visible symptoms. The

pathogen In biology, a pathogen ( el, πάθος, "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 ...

, sandal spike phytoplasma, was first detected by electron microscopy in 1969. Phytoplasmas are pleomorphic and fragile organisms occupying relatively small areas within the

sieve tube Sieve elements are specialized cells that are important for the function of phloem, which is a highly organized tissue that transports organic compounds made during photosynthesis. Sieve elements are the major conducting cells in phloem. Conductin ...

s (phloem) of the host plants. The major obstacle limiting research on phytoplasma disease is that the organism has not so far been isolated and cultivated ''in vitro''. Sandal spike phytoplasma is a pleomorphic microorganism and are the smallest organism capable of independent replication (i.e. does not need a host). The pathogen is around 0.4 to 1.0 micrometer in diameter, has a

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

, ribosome and DNA. The amino acids cysteine, methionine and

tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...

are absent in sandal spike phytoplasma.

Detection of sandal spike phytoplasma

For non-specific detection of sandal spike phytoplasma by light microscopy Giemsa and Dienes’ stain are employed. Aniline blue, Hoechst 33258 and DAPI stain are used in the non-specific detection by fluorescence microscopy. Scientists at

Kerala Forest Research Institute The Kerala Forest Research Institute (KFRI) is an organisation based in Peechi, in Thrissur, India. It was established in 1975 by the Government of Kerala as part of its Science and Technology Department, and in 2003 became part of the Kerala ...

, India had reported employing the polymerase chain reaction technique for detecting sandal spike phytoplasma. The pathogen belongs to group I of the major phytoplasma groups. For raising

polyclonal antibodies Polyclonal antibodies (pAbs) are antibodies that are secreted by different B cell lineages within the body (whereas monoclonal antibodies come from a single cell lineage). They are a collection of immunoglobulin molecules that react against ...

against sandal spike phytoplasma, the pathogen is purified by differential filtration technique. The antibody thus raised detects the pathogen by ELISA, Dot Immuno Binding Assay and Immuno-microscopy.

References

Bacterial tree pathogens and diseases {{plant-disease-stub