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Title: First report of new phytoplasma diseases associated with soybean, sweet pepper, and passion fruit in Costa Rica

Author
item Villalobos, W
item Moreira, L
item Rivera, C
item Lee, Ing Ming

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2008
Publication Date: 2/1/2009
Citation: Villalobos, W., Moreira, L., Rivera, C., Lee, I. 2009. First report of new phytoplasma diseases associated with soybean, sweet pepper, and passion fruit in Costa Rica. Plant Disease. 93:201.

Interpretive Summary: Phytoplasmas are uncultured bacteria that lack a cell wall and that cause several hundred economically important diseases in plants worldwide. Because of the advance in molecular tools for detection and identification of phytoplasmas, many previously unknown or newly emerged diseases have been diagnosed to be caused by phytoplasmas in the last decades. Thus far more than 1000 phytoplasma strains have been reported and classified into 29 distinct groups and many subgroups. Recently, new diseases with characteristic symptoms induced by phytoplasmal infection occurred in soybean, sweet pepper, and passion fruit in Costa Rica. In collaboration with scientists from Costa Rica, we detected a new phytoplasma from all three crops. This phytoplasma is distinct from all the existing phytoplasmas previously reported and represents a new taxon most closely related to 16SrXII group phytoplasmas.This is the first report that a new phytoplasma is associated with these crops in Costa Rica. There is potential for these diseases to spread in the future. The information will aid implementation of quarantine regulation and it will help extension workers and plant diagnosticians in Costa Rica to determine how to combat the disease.

Technical Abstract: A new soybean disease outbreak occurred in 2002 in a soybean (Glycine max) plantation in Alajuela Province, Costa Rica. Symptoms in the affected plants included general stunting, little leaf, formation of excessive buds, and aborted seed pods. Another two diseases occurred in sweet pepper (Capsicum annuum) fields and in one passion fruit (Passiflora edulis) vine. Affected sweet pepper plants produced unusual dark green leaves; some of which exhibited rugose symptom with zig-zag of the mid-vein and purple vein discoloration, while the affected passion fruit vine exhibited bud proliferation. These symptoms resemble those caused by phytoplasmal infection. A nested PCR using primer pair P1/P7 followed by R16F2n/R16R2 (1) was employed for the detection of putative phytoplasmas that might be associated with symptomatic plants. All seven symptomatic plants (three soybeans, three sweet peppers and one passion fruit) but not healthy controls yielded positive for phytoplasmas. Restriction fragment length polymorphism (RFLP) analysis of nested PCR products using restriction enzymes AluI, BfaI, HhaI, MseI, and RsaI indicated that the three diseases were associated with very similar or identical phytoplasma. RFLP patterns and sequence analysis of cloned 16S rDNAs revealed that this phytoplasma is distinct from all the existing phytoplasmas previously reported and represents a new taxon most closely related to 16SrXII group (1) phytoplasmas. This is the first report that a new phytoplasma is associated with soybean, sweet pepper, and passion fruit in Costa Rica.