Sandal spike phytoplasma
Encyclopedia
Sandal a semi-root parasitic tree
is the source of the East Indian sandalwood
and oil
. Spike disease caused by phytoplasma
is the major disease
of sandalwood
.
The disease is noticed in all major sandal-growing states of India
. 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
, sandal spike phytoplasma, was first detected by electron microscopy
in 1969. Phytoplasmas are pleomorphic and fragile organisms occupying relatively small areas within the sieve tubes (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 (ie., does not need a host). The pathogen is around 0.4 to 1.0 micrometer in diameter, has a cell membrane
, ribosome
and DNA
. The amino acids cysteine
, methionine
and tryptophan
are absent in sandal spike phytoplasma [1].
Scientists at Kerala Forest Research Institute
, India had reported employing the polymerase chain reaction technique for detecting sandal spike phytoplasma [3]. The pathogen belongs to group I of the major phytoplasma groups.
For raising polyclonal antibodies against sandal spike phytoplasma, the pathogen is purified by differential filtration technique [1]. The antibody thus raised detects the pathogen by ELISA, Dot Immuno Binding Assay [1] and Immuno-microscopy [4].
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
is the source of the East Indian sandalwood
Sandalwood
Sandalwood is the name of a class of fragrant 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. As well as using the harvested and cut wood in-situ, essential oils are also extracted...
and oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
. Spike disease caused by phytoplasma
Phytoplasma
Phytoplasma are specialised bacteria that are obligate parasites of plant phloem tissue and transmitting insects . They were first discovered by scientists in 1967 and were named mycoplasma-like organisms or MLOs. They cannot be cultured in vitro in cell-free media...
is the major disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
of sandalwood
Sandalwood
Sandalwood is the name of a class of fragrant 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. As well as using the harvested and cut wood in-situ, essential oils are also extracted...
.
The disease is noticed in all major sandal-growing states of India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
. 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
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
, sandal spike phytoplasma, was first detected by electron microscopy
Electron microscope
An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...
in 1969. Phytoplasmas are pleomorphic and fragile organisms occupying relatively small areas within the sieve tubes (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 (ie., does not need a host). The pathogen is around 0.4 to 1.0 micrometer in diameter, has a cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
, ribosome
Ribosome
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....
and DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
. The amino acids cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
, methionine
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
and tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
are absent in sandal spike phytoplasma [1].
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 [2]Scientists at Kerala Forest Research Institute
Kerala Forest Research Institute
The Kerala Forest Research Institute is an research organisation based in Peechi, in Thrissur, India. The Institution 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 State Council for Science, Technology...
, India had reported employing the polymerase chain reaction technique for detecting sandal spike phytoplasma [3]. The pathogen belongs to group I of the major phytoplasma groups.
For raising polyclonal antibodies against sandal spike phytoplasma, the pathogen is purified by differential filtration technique [1]. The antibody thus raised detects the pathogen by ELISA, Dot Immuno Binding Assay [1] and Immuno-microscopy [4].