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First Report of a Phytoplasma Associated with Witches'-Broom of the Giant Coral Tree (Erythrina poeppigiana, Fabaceae) in Costa Rica

The giant coral tree (Erythrina poeppigiana, Fabaceae) is a common shade tree in coffee plantations in Costa Rica. Coral trees are pruned to decrease fungal infections and increase nitrogen fixation. Recently, severe shoot proliferation, internodes shortening, and leaf reduction were observed in pruned shade trees in the south of San José Province, Costa Rica. Leaf samples from 10 symptomatic E. poeppigiana trees were collected. Also, two samples from symptomless coral trees were collected from areas free of witches'-broom. Total DNA was extracted from 0.5 g of petiole tissue from all samples with the plant extraction mini kit (Qiagen GmbH, Hilden, Germany) with a modified protocol (2) and assayed by nested PCR with phytoplasma universal rDNA primers (P1/P7) (1) and R16F2n/R16R2 (3). All symptomatic trees tested positive for phytoplasmas by PCR, yielding the expected 1.2-kb band. DNA from the symptomless trees was not amplified by PCR. The restriction fragment length polymorphism analyses (HaeIII, AluI, RsaI, BfaI, HpaII, KpnI, HhaI, and MseI) and the sequence of the 1.2-kb PCR fragment (GenBank Accession No. DQ485305) revealed that the phytoplasma associated with coral tree witches'-broom belongs to the aster yellows phytoplasma group (16SrI) (4). To our knowledge, this is the first report of a phytoplasma belonging to the aster yellow group causing witches'-broom in the Erythrina genus.

References: (1) S. Deng and C. Hiruki. J. Microbiol. Methods 14:53, 1991. (2) M. J. Green et al. Plant Dis. 83:482, 1999. (3) D. E. Gundersen and I. M. Lee. Phytopathol. Mediterr. 35:144, 1996. (4) I. M Lee et al. Int. J. Syst. Bacteriol.48:1153, 1998.