BIORATIONAL CONTROL METHODS FOR INSECT PESTS OF POTATO
Location: Fruit and Vegetable Insect Research
Title: First Report of Candidatus Liberibacter solanacearum in Tomato Plants in Mexico
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2009
Publication Date: September 10, 2009
Citation: Munyaneza, J.E., Sengoda, V.G., Crosslin, J., Garzon-Tiznado, J.A., Cardenas-Valenzuela, O.G. 2009. First Report of Candidatus Liberibacter solanacearum in Tomato Plants in Mexico. Plant Disease. 93:1076.
Interpretive Summary: Zebra chip, an emerging and important potato disease that is causing millions of dollars in losses to the potato industry in United States, Mexico, Central America, and New Zealand, has recently been associated with a new species of the bacterium Liberibacter transmitted by the potato psyllid. Although this plant pathogen has so far been found to infect few other important crops, little is known on its plant host range and geographical distribution. Researchers at USDA-ARS Wapato and Prosser, in collaboration with scientists at Universidad Autonoma de Sinaloa in Mexico conducted studies to identify crops that are affected by this damaging plant pathogen. For the first time, it was discovered that, in Mexico, this bacterium infects and causes disease in tomatoes. Information from this research will help affected vegetable producers in North America reduce damage caused by this important pathogen by effectively managing the potato psyllid, its insect vector.
Tomato (Lycopersicon esculentum Mill.) plants exhibiting symptoms that resemble those of permanent yellowing disease (locally known as “permanente del tomate”) that is associated with phytoplasmas and/or ‘Candidatus Liberibacter solanacearum’ infection were observed in the state of Sinaloa, México in March 2009. Affected plants showed overall chlorosis, severe stunting, leaves rolling upward, leaf cupping, purple discoloration of veins, abnormal floral structures, excessive branching of axillary shoots, and leaf scorching. To investigate whether liberibacter is associated with permanent yellowing disease of tomato in México, eight symptomatic and five asymptomatic tomato plants were collected from tomato fields in La Cruz de Elota and Culiacán, Sinaloa, México and tested for this bacterium by PCR. Total DNA was extracted from the vascular tissue of symptomatic and asymptomatic plants with CTAB buffer. DNA samples were tested by PCR using primer pair OA2/OI2c specific for 16S rDNA and primer pair CL514F/R designed from ribosomal protein genes. Of the eight symptomatic tomato plants, five (62.5%) and four (50%) yielded the expected 1,168 bp 16S rDNA (OA2/OI2c) and 669 bp CL514F/R amplicons, respectively, indicating the presence of liberibacter. Nucleic acid from asymptomatic plants yielded no product with these primers. Three amplicons generated from symptomatic plants with each primer pair were cloned into pCRII-TOPO plasmid vectors (Invitrogen, Carlsbad, CA) and three clones of each of these amplicons were subsequently sequenced in both directions (ACGT, Inc., Wheeling, IL). BLAST analysis of the symptomatic tomato plants OA2/OI2c consensus sequence showed 100% identity to liberibacter 16S rDNA sequences amplified from zebra chip (ZC)-infected potato tubers from Lancaster, CA and Weslaco, TX. The symptomatic tomato plants CL514F/R consensus sequence was 100% identical to analogous rplJ and rplL ‘Ca. Liberibacter solanacearum’ ribosomal protein gene sequences amplified from ZC-infected potato tubers from Lancaster, CA and from several solanaceous plants in New Zealand. The OA2/OI2c sequence was also identical to the 16S sequence of Ca. Liberibacter psyllaurous. To our knowledge, this is the first report of ‘Ca. Liberibacter solanacearum’ associated with tomatoes in México.