First Report of the Detection of ‘Candidatus Liberibacter’ Species in Zebra Chip Disease-Infected Potato Plants in the United States

Abstract

Zebra chip (ZC), an emerging disease causing economic losses to the potato chip industry, has been reported since the early 1990s in Central America and Mexico and in Texas during 2000 (4). ZC was subsequently found in Nebraska, Colorado, New Mexico, Arizona, Nevada, California, and Kansas (3). Severe losses to potato crops were reported in the last few years in Mexico, Guatemala, and Texas (4). Foliar symptoms include purple top, shortened internodes, small leaves, enlargement of the stems, swollen axillary buds, and aerial tubers. Chips made from infected tubers exhibit dark stripes that become markedly more visible upon frying, and hence, are unacceptable to manufacturers. Infected tubers may or may not produce plants when planted. The causal agent of ZC is not known and has been the subject of increased investigation. The pathogen is believed to be transmitted by the potato psyllid, Bactericera cockerelli, and the association of the vector with the disease is well documented (3). Following the report of a potential new liberibacter species in solanaceous crops in New Zealand, we sought to identify this liberibacter species in plants with symptoms of the ZC disease. Six potato plants (cv. Russet Norkota) exhibiting typical ZC symptoms were collected in Olton, TX in June of 2008. DNA was extracted from roots, stems, midribs, and petioles of the infected plants using a FastDNA Spin Kit and the FastPrep Instrument (Qbiogene, Inc., Carlsbad, CA). Negative controls from known healthy potato plants were included. PCR amplification was carried out with ‘Candidatus L. asiaticus’ omp primers (1), 16S rDNA primers specific for ‘Ca. L. asiaticus’, ‘Ca. L. africanus’, and ‘Ca. L. americanus’ (1), and 16S rDNA primers OA2 (GenBank Accession No. EU834130) and OI2c (2). Amplicons from 12 samples were directly sequenced in both orientations (McLab, San Francisco CA). PCR amplifications using species-specific primers for the citrus huanglongbing liberibacter were negative. However, 1.1- and 1.8-kb amplicons were obtained with the OA2/OI2C and omp primers, respectively. The sequences for the rDNA were submitted to NCBI GenBank (Accession Nos. EU884128 and EU884129). BLASTN alignment of the 16S rDNA sequences obtained with primers OA2 and OI2c revealed 99.7% identity with a new species of ‘Ca. Liberibacter’ identified in New Zealand affecting potato (GenBank Accession No. EU849020) and tomato (GenBank Accession No. EU834130), 97% identity with ‘Ca. L. asiaticus’, and 94% with ‘Ca. L. africanus’ and ‘Ca. L. americanus’. The neighbor-joining phylogenetic tree constructed using the 16S rDNA fragments delineated four clusters corresponding to each of the liberibacter species. These results confirm that ‘Ca. Liberibacter’ spp. DNA sequences were obtained from potatoes showing ZC-like symptoms, suggesting that a new species of this genus may be involved in causing ZC disease. To our knowledge, this is the first report of the detection of ‘Ca. Liberibacter’ spp. in potatoes showing ZC disease in the United States. References: (1) C. Bastianel et al. Appl. Environ. Microbiol. 71:6473, 2005. (2) S. Jagoueix et al. Mol. Cell. Probes 10:43, 1996. (3) J. E. Munyaneza et al. J. Econ. Entomol. 100:656, 2007. (4) G. A. Secor and V. V. Rivera-Varas. Rev. Latinoamericana de la Papa (suppl.)1:1, 2004.

Seasonal Occurrence and Abundance of the Potato Psyllid, Bactericera cockerelli, in South Central Washington

“…However, recent studies conducted in US, Mexico, and New Zealand have shown that zebra chip is associated with a previously undescribed species of the bacterium Candidatus Liberibacter vectored by the potato psyllid, Bactericera cockerelli Sulc (Munyaneza et al 2007a, b;Hansen et al 2008;Liefting et al 2008;Munyaneza et al 2008;Abad et al 2009;Crosslin and Bester 2009;Crosslin and Munyaneza 2009;Liefting et al 2009a, b;Lin et al 2009;Munyaneza et al 2009;Secor et al 2009). Effective monitoring and control of the potato psyllid are essential in order to better manage zebra chip in potatoes (Goolsby et al 2007;Gharalari et al 2009;Munyaneza, unpublished data).…”

Efecto de antioxidantes y señalizadores en plantas de papa (Solanum tuberosum L.) infectadas con Candidatus Liberibacter solanacearum bajo condiciones de invernadero

“…En Estados Unidos la enfermedad causada en la papa por Ca. L. solanacearum se le conoce como Zebra Chip (ZC) debido al pardeamiento que ocasiona en la pulpa del tubérculo (Abad et al, 2009;Liefting et al, 2009), e inicialmente a la bacteria se le nombro Candidatus Liberibacter psyllaurous (Hansen et al, 2008). Otro problema sanitario es el Amarillamiento del Psílido (AP), ocasionado según algunos autores por la inyección de toxinas que realiza el psílido Bactericera cockerelli Sulc.…”

'Candidatus Liberibacter solanacearum', associated with plants in the family Solanaceae

“…The remainder of the 16S rRNA gene was sequenced and phylogenetic analysis showed that it is distinct from the three citrus-infecting liberibacter species described previously ). Subsequently, with the development of a specific PCR diagnostic method, this new liberibacter was also detected in potato (Solanum tuberosum), tamarillo (Solanum betaceum), cape gooseberry (Physalis peruviana) (Liefting et al, 2008a, b;Abad et al, 2009) and chilli (Capsicum sp.). A 1.7 kb fragment of the b operon containing the ribosomal proteins L10 (rplJ) and L12 (rplL) and the RNA polymerase beta subunit (rpoB) was amplified using the primer pair fp 1898/rp 1897 (Planet et al, 1995).…”

“…We propose that the novel liberibacter species identified in solanaceous plants is named after its plant host family rather than the geographical region. Although this liberibacter species was first identified in New Zealand, it has subsequently been detected in potato plants exhibiting zebra chip symptoms in the USA (Abad et al, 2009). Zebra chip disease of potato was first reported in Mexico in 1994 and then in the USA in 2000 (Secor & Rivera-Varas, 2004).…”