Phytoplasma

Phytoplasmas are cell wall deficient bacteria that grow as obligate parasites of plant phloem.

Phytoplasmas were discovered in 1967 Since 1994, they are a separate species ( Candidatus " Phytoplasma " ) assigned, previously they were of the genus Mycoplasma attributed and called MLO ( Mycoplasma-like organism English ).

Description

These members of the class Mollicutes are transmitted from insects such as cicadas phloemsaugenden from plant to plant; therefore the insects act as vectors. The bacteria are outside of plants or insects do not survive and therefore not be cultured in vitro. They are usually less than 1 micron in size and have a pleiomorphe or filamentous form. In comparison to the Bacillus / Clostridium ancestors their genome is greatly reduced as adaptation to a parasitic mode of life; artabhängig the genome size is 530-1350 kbp. It lacks genes that are necessary for the synthesis of ATP, amino acids and nucleotides. Accordingly, phytoplasmas are dependent on the import of such metabolites from the host cells. Among the known host plants include, inter alia, Crops such as coconut palm, cherry and apple trees, grape vines, sugar cane and rice. The pathogen causes leaf yellowing, necrosis and growth abnormalities such as phyllody (formation of sheet-like structures instead of flowers). In summary, these symptoms are referred to as Phytoplasmose. The berries of affected vines shrink when ripe, are acidic and can fall off. The leaf yellowing caused by an inhibited chlorophyll synthesis and by an impaired transport of assimilates in the leaves. Phyllody results from effects of phytoplasmas on the regulation of flowering genes. Phytoplasmas infestation can be checked with PCR testing. To avoid crop losses, resistant varieties are grown and fights the phytoplasma -carrying insects.

Phytoplasmoses

Phytoplasmas are the causative agents of a variety of plant diseases, the so-called phytoplasmoses. Phytoplasmoses cause considerable economic damage, as they also damage many crops. Common symptoms of phytoplasmoses are leaf yellowing, stunting growth and broom.

Some phytoplasmoses are:

• Apple proliferation ( Candidatus Phytoplasma mali )
• Pear decline ( Candidatus Phytoplasma pyri)
• Rubus Stauche at Brambleberry
• Blackwood disease in grapevines
• Stone Fruit Yellows ESFY ( Candidatus phytoplasma prunorum )