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Title: FIRST REPORT OF A SUBGROUP 16SRI-B PHYTOPLASMA INFECTING CHAYOTE [SECHIUM EDULE (JACQ.) SWARTZ] AND TWO OTHER CUCURBITS IN COSTA RICA

Author
item VILLALOBOS, W - UNIV DE COSTA RICA
item MOREIRA, L - UNIV DE COSTA RICA
item RIVERA, C - UNIV DE COSTA RICA
item Bottner, Kristi
item Lee, Ing Ming

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: An outbreak of a new disease was observed in several chayote (Sechium edule) fields in the chayote commercial production area at Ujarras Valley, Cartago Province, Costa Rica. The infected chayote plants exhibited witches'-broom symptoms suggestive of phytoplasmal infection. Using a PCR-based procedure developed earlier in our laboratory, we have detected phytoplasmas in such diseased chayote and in two other cucurbit species (tacaco, S. tacaco, and Rytidostylis carthaginensis) growing in the vicinity of chayote fields. RFLP (finger printing) analysis of the PCR products indicated that a phytoplasma, belonging to subgroup 16SrI-B in the aster yellows phytoplasma group, was associated with all three cucurbit species exhibiting disease symptoms. This is the first report of the presence of a phytoplasma in naturally infected cucurbits in Costa Rica. The phytoplasma is different from the one reported to be associated with chayote witches'-broom disease in Brazil. The information will be useful to extension workers and diagnosticians, and to regulatory agencies for implementation of new quarantine regulations.

Technical Abstract: An outbreak of a new disease was observed in several chayote (Sechium edule) fields in the chayote commercial production area at Ujarras Valley, Cartago Province, Costa Rica. The infected chayote plants exhibited witches'-broom symptoms suggestive of phytoplasmal infection. Two other cucurbit species (tacaco, S. tacaco, and Rytidostylis carthaginensis) growing near the chayote fields also exhibited similar symptoms. Nested PCR using universal primer pair P1/P7 followed by R16F2n/R16R2 was employed for the detection of the putative phytoplasma (s)associated with infected cucurbits. Phytoplasmas were detected from all symptomatic samples tested. All asymptomatic samples tested negative for phytoplasma. RFLP analysis of PCR products (16S rDNA sequences) with eight restriction enzymes (RsaI, HhaI, KpnI, BfaI, HaeIII, HpaII, AluI, and MseI) revealed that a phytoplasma belonging to subgroup 16SrI-B in the aster yellows phytoplasma group (16SrI) was associated with chayote witches'-broom (CWB). The same or very similar phytoplasma was also associated with infected tacaco and R. carthaginensis plants. The P1/P7-PCR products from chayote and tacaco samples were cloned and sequenced. The 16SrDNA sequences confirmed the identity of the associated phytoplasma. This is the first report of the presence of a phytoplasma belonging to aster yellows group, subgroup 16SrI-B in naturally infected cucurbits in Costa Rica.