Elimination of phytoplasmas as causal agents of macadamia decline and non-ripening of papaya. (36)

Wayne B. Borth, Diane E. Ullman, Vincent P. Jones, Francis Zee, John S. Hu


Macadamia (Macadamia integrifolia Maiden & Betche) decline and non-ripening of papaya (Carica papaya L.) fruit are disorders of unknown aetiology that occur in Hawaii. Preliminary evidence obtained with the DNA fluorochrome DAPI suggested the possible involvement of phytoplasmas with these disorders. Using polymerase chain reaction (PCR) assays with a variety of phytoplasma-specific primers and grafting, the possible association of phytoplasmas with these disorders were studied. Detectable PCR amplicons with phytoplasma-specific sequences were not produced from any symptomatic plants using PCR primers that have been shown to recognize nucleic acid sequences from many different phytoplasmas. Grafts of symptomatic tissues onto healthy seedling stocks did not result in any development of symptoms in grafted hosts. There is no evidence from these studies that indicates the association of phytoplasmas with these disorders.


Phytoplasma; Polymerase chain reaction; Macadamia; Papaya; Sophonia; Hawaii

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