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A Light and Transmission Electron Microscope Study of a Black Locust Tree, Robinia pseudoacacia (Fabaceae), Affected by Witches’‐Broom, and Classification of the Associated Phytoplasma
Author(s) -
Chapman G. B.,
Buerkle E. J.,
Barrows E. M.,
Davis R. E.,
Dally E. L.
Publication year - 2001
Publication title -
journal of phytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 60
eISSN - 1439-0434
pISSN - 0931-1785
DOI - 10.1046/j.1439-0434.2001.00673.x
Subject(s) - biology , locust , sieve tube element , broom , robinia , phytoplasma , phloem , paracrystalline , botany , restriction fragment length polymorphism , polymerase chain reaction , crystallography , ecology , gene , biochemistry , chemistry
Light and transmission electron microscopy of phloem sieve‐tube elements, companion cells, and parenchymal cells in thin and ultrathin sections of small and medium rachises and small, medium and large leaflets of a black locust tree, Robinia pseudoacacia L., affected by witches’‐broom disease revealed (in the small and medium rachises and leaflets) structures that were characteristic of phytoplasmas, and crystal‐like inclusions in the phloem sieve‐tube members. A crystal‐like inclusion was also seen in a companion cell. Paracrystalline arrays were seen only (and very rarely) in phloem sieve‐tube elements of medium rachises. Some elements contained several crystal‐like inclusions and each inclusion had fracture planes. The crystal‐like inclusions and paracrystalline arrays apparently have not been previously reported in the black locust. The paracrystalline arrays and crystal‐like inclusions may merely be by‐products of the plant’s metabolic activity. Extensive additional work would be required to establish the precise relationship (if any) of the arrays and inclusions to the black locust, witches’‐brooming and/or phytoplasmas. Results from analysis of 16S rRNA gene sequences amplified by the polymerase chain reaction indicated for the first time that the phytoplasma associated with black locust witches’‐broom is a member of group 16 SrIII (peach X‐disease) phytoplasma group. This raised the question of whether black locust may be a significant source of the phytoplasma for infection of other plants, especially agricultural crops.