Browsing by Autor "P. Jones"

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‘Brotes grandes’ (big bud) of potato: a new disease associated with a 16SrI‐B subgroup phytoplasma in Bolivia
(Wiley, 2005) P. Jones; Y. Arocha; O. Antesana; E. Montellano; P. Franco
Potatoes are the main crop of smallholder farmers in the Valles Cruceños, Santa Cruz Province, Bolivia. During surveys carried out from 2000 to 2003, a disease locally known as ‘brotes grandes’ (BG, ‘big bud’), was prevalent on crops in the valleys of Chilon, Saipina, Pulquina and Comarapa, where up to 90% of plants were affected in some fields. Symptoms included tuber-like growths in leaf axils, varying in size and colour from red to purple or black and bearing terminal, adventitious leaves. Tubers often produced hair-like shoots, reducing their quality and yield. Previously, this syndrome was presumed to be rhizoctoniosis, caused by basal stem infection by Rhizoctonia solani (teleomorph, Thanatephorus cucumeris). However, R. solani was absent from all diseased plants examined in the present study. As other potato diseases similar to BG have been attributed to phytoplasmas in Australia (Harding & Teakle, 1993), Poland (Hamilton, 2000), Canada (Khadhair et al., 2003) and Mexico (Martínez-Soriano et al., 1999), tissues from Bolivian plants were indexed by nested PCR (nPCR) using phytoplasma universal rRNA primer pairs P1/P7 and R16F2n/R16R2. nPCR products resulting from 43/50 BG samples and digested separately with HaeIII, RsaI or AluI endonuclease all produced identical RFLP profiles. RFLP profiles of nPCR products amplified from three samples of the mora-mora vine (Serjania perulacea) with little-leaf symptoms in hedgerows surrounding potato fields in La Tranca, Santa Cruz Province, were indistinguishable from BG profiles. 16S rDNA sequences derived from PCR products shared 99% sequence homology among BG phytoplasmas. Sequences from the phytoplasmas obtained from potato (accession no. AY725209) and from S. perulacea (accession no. AY725210) were each very similar (98%) to that of ash witches’ broom phytoplasma (accession no. AY568302). This is the first report of a phytoplasma of the aster yellows (16SrI) group associated with a potato disease in Bolivia. Work in the UK was done under Defra plant health licence no. PHL 174B/4612(09/20003).
‘Candidatus Phytoplasma lycopersici’, a phytoplasma associated with ‘hoja de perejil’ disease in Bolivia
(Microbiology Society, 2007) Y. Arocha; O. Antesana; E. Montellano; Pablo Franco; G. Plata; P. Jones
New diseases known locally as 'hoja de perejil' of tomato (Lycopersicon esculentum Mill) and 'brotes grandes' of potato (Solanum tuberosum L.) were first recognized in surveys of production fields in Bolivia during 2000-2003. Alfalfa (Medicago sativa) witches' broom and little leaf diseases of native weeds Morrenia variegata and mora-mora (Serjania perulacea) were also identified near to production fields. Phytoplasma aetiology was attributed to each of these diseases following detection and initial identification of aster yellows group (16SrI) phytoplasmas in all five diseased plant species. While potato, alfalfa and mora-mora plants contained indistinguishable 16SrI-B strains, 'hoja de perejil' (THP) and morrenia little leaf (MVLL)-associated phytoplasma strains shared 97.5 % 16S rRNA gene sequence similarity with 'Candidatus Phytoplasma asteris' and related strains and <95 % similarity with all other 'Candidatus Phytoplasma' species. Phylogenetic analysis of 16S rRNA gene sequences indicated that the THP and MVLL phytoplasmas represent a novel lineage within the aster yellows (16SrI) group and, on the basis of unique 16S rRNA gene sequences, we propose that THP and MVLL phytoplasmas represent 'Candidatus Phytoplasma lycopersici', with THP as the reference strain.
First report of an isolate of ‘ <i>Candidatus</i> Phytoplasma australiense’ associated with a yellow leaf roll disease of peach ( <i>Prunus persicae</i> ) in Bolivia
(Wiley, 2005) P. Jones; Y. Arocha; O. Antesana; E. Montilliano; P. Franco
Phytoplasmas, prokaryote plant pathogens, have been reported to cause peach yellow leaf roll (PYLR) (Smart et al., 1996) and peach red leaf (PRL) diseases. The PYLR phytoplasma belongs to the 16SrX Apple proliferation group (‘Candidatus Phytoplasma mali’) (Seemüller & Schneider, 2004), but PRL still has not been assigned to a subspecific lineage in ‘Candidatus Phytoplasma asteris’ (Lee et al., 2004). Symptoms similar to PYLR disease were observed in a peach plantation at San Isidro, Santa Cruz Province, Bolivia during a survey in 2003. Older leaves had symptoms of yellowing of the leaf margin and rolling, drying and necrosis. Young leaves were tightly rolled and yellow, and proliferation of shoots was evident along branches. Many trees were dead or dying. Samples of young shoots and leaves were taken from affected and apparently healthy trees and returned to Rothamsted Research, Harpenden, UK. Total DNA was extracted and indexed by nested PCR with generic phytoplasma rDNA primers P1/P7 and R16F2n/R16R2. PCR products were characterized by RFLP analysis using the restriction endonucleases HaeIII, RsaI and AluI and direct sequencing. All samples from affected trees gave a 1250 bp PCR product and identical RFLP profiles. Sequence of phytoplasma rDNA (accession no. AY 725212) was compared with others in the GenBank database using blast. The greatest similarity (98%) was with papaya dieback phytoplasma (accession no. Y10095) from Australia, a member of the 16SrXII Stolbur group (‘Candidatus Phytoplasma australiense’) (Firrao et al., 2004). This is the first report of a peach yellow leaf roll-like disease in Bolivia, and the first record of the presence of a Stolbur group phytoplasma in peach. These results contribute to the known diversity of phytoplasmas found in peach and in Bolivian crops. This work was supported by the Department for International Development (UK) through the Global Plant Clinic. Work in the UK was done under Defra plant health licence no. 174B/4612(09/2003). Y. Arocha thanks the Royal Society (UK) for financial support.
‘Hoja de perejil’ (parsley leaf) of tomato and morrenia little leaf, two new diseases associated with a phytoplasma in Bolivia
(Wiley, 2005) P. Jones; Y. Arocha; O. Antesana; E. Montellano; P. Franco
Tomatoes (Lycopersicon esculentum), an important cash crop for smallholder farmers in the hillside production systems of the Valles Cruceños, Santa Cruz Province and Rio Chico, Sucre Province, Bolivia, were surveyed during 2002–3. Symptoms of ‘hoja de perejil’ start with adventitious sprouting of axillary buds and rapid elongation of side shoots, which break through the crown of normal leaves. Leaves of the side shoots are small and fern-like and, as the season progresses, large bushy plants are produced. Flowers are reduced in size and do not appear to set fruit, but some fruit may be produced on the early normal growth. Affected plants were screened for virus using lateral flow kits (Pocket Diagnostics®), ELISA and electron microscopy. Only Tomato mosaic virus was identified but this was not consistently associated with ‘hoja de perejil’. DNA was extracted from affected plants and tested by nested PCR for phytoplasma using generic rDNA primers P1 (Deng & Hiruki, 1991)/P7 (Schneider et al., 1995) and R16F2n/R16R2 (Gundersen & Lee, 1996). Phytoplasma products were confirmed using the endonucleases HaeIII, RsaI and AluI, and by direct sequencing of the 16S/23S spacer region (SR) with P4 (Smart et al., 1996)/P7 primers. During the tomato crop surveys, plants of Morrenia variegata (Asclepiadaceae), a vine growing in hedgerows, were found around affected tomato fields near San Rafael, Santa Cruz Province, that showed symptoms of little leaf. DNA was extracted from these plants and indexed for phytoplasma as above. Amplimers (1250 bp) with identical RFLP profiles were consistently obtained from ‘hoja de perejil’ and M. variegata with little leaf. SR sequences from ‘hoja de perejil’ (GenBank accession no. AY725208) and morrenia little leaf (accession no. AY725207) were compared with those of other phytoplasmas in GenBank using BLAST. They showed a maximum (91%) homology with phytoplasmas from the 16SrI Aster yellows group. This is the first report of ‘hoja de perejil’ disease of tomato, where infection rates of over 60% were seen in some fields of the most popular cultivar Rio Grande. This is also the first report of morrenia little leaf disease and its association with a phytoplasma. The BLAST results suggest that the phytoplasma found associated with these diseases may belong to a new 16Sr phytoplasma group. Work in the UK was carried out under Defra plant health licence no. PHL 174B/4612 (09/2003).