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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #248927

Title: First Report of "Candidatus Liberibacter psyllaurous" (synonym "Ca. L. solanacearum") Associated with 'Tomato Vein-Greening' and 'Tomato psyllid yellows' Diseases in Commercial Greenhouses in Arizona

Author
item BROWN, J - University Of Arizona
item REHMAN, M - Hazara University
item ROGAN, D - University Of Arizona
item Martin, Robert
item IDRIS, M - University Of Arizona

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2009
Publication Date: 2/4/2010
Citation: Brown, J.K., Rogan, D., Idris, A.M., Martin, R.R., Rehman, M. 2010. First report of "Candidatus Liberibacter psyllaurous" (synonym "Ca. L. solanacearum") associated with 'tomato vein-greening' and 'tomato psyllid yellows' diseases in commercial greenhouses in Arizona. Plant Disease. 94(3):376.

Interpretive Summary: Tomato plants in two independent, commercial greenhouses in Arizona were infested with the potato psyllid during 2006 and 2007 and over 60% and ~20% of plants in GH-1 and GH-2, respectively, exhibited leaf curling, stunting, and shortened internodes. Additionally, plants in GH-1 showed vein-greening symptoms. Initial attempts to detect phytoplasmas in diseased plants yielded PCR products of the expected size. However, when these products were sequenced and compared to DNA databases, they were shown to be Liberibacter, with 99-100% seqeunce identity in the 16S ribosomal DNA. These results were only obtained from plants in GH-1. Similar results were obtained with additional PCR tests confirming the presence of Liberibacter only in plants that showed the vein-greening symptoms. When psyllids from plants with vein greening symptoms were transferred to healthy tomato seedlings, these plants also developed the vein-greening symptoms and tested positive for the Liberibacter.

Technical Abstract: During 2006-2007, tomato plants in two independent, commercial greenhouses in Arizona were infested with potato psyllid Paratrioza cockerelli. Over 60% and ~20% of plants in GH-1 and GH-2, respectively, exhibited leaf curling, stunting, and shortened internodes, and GH-1 plants also showed vein-greening symptoms. Total nucleic acids were isolated from ten symptomatic leaves collected from each greenhouse. The primers PA F5’-TTGGGCGTAAAGGGTGC and PD R5’-GCGATTAC TAGCGATTCC were used to amplify a suspect phytoplasma 16S rDNA, to yield ~900 bp. Eight of ten GH-1 and five of ten GH-2 samples yielded a ~900 bp PCR product. Five PCR products per sample were cloned, and the DNA sequence was determined for 10 clones each. BLAST analysis of GH-1 samples revealed a 16S rDNA sequence (n=3) [GQ926917] 100% identical to Ca. Liberibacter psyllaurous [EU812558]. The remaining GH-1 and all GH-2 sequences shared 53-86% identity with divergent 16S rDNAs amplified from soil or water. To improve PCR specificity, the primers 5'-F-gttcggaataactgggcgta and 3-'R-tagggactgccggtgataag were designed based on the obtained 16S rDNA and EU812559. They were used to amplify a ~750 bp fragment (trimmed, 680) of the 16S rDNA from: (i) DNA extracts of greenhouse-infected samples, (ii) laboratory grown tomato plants infested in the 6-8 leaf stage with psyllids collected in GH-1 and GH-2 (six+ generations), and (iii) lysis (1) from colony-reared psyllids. A PCR product of the expected size (~750 bp) was obtained from GH-1 DNA extracts from tomato, GH-1 psyllid-colony tomato plants [GQ926918], and GH-1 psyllids [GQ926919] but not from the analogous GH-2 samples. All laboratory plants to which GH-1 and GH-2 psyllids were transferred developed leaf curling, stunting, and shortened internodes, whereas only tomato plants infested with psyllids from GH-1 tested positive for Ca. Liberibacter and developed vein-greening symptoms like those originally observed in GH-1.