New Disease Reports
New Disease Reports (2004) 10, 18.
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Brotes grandes (big bud) of potato: a new disease associated with a 16SrI-B subgroup phytoplasma in Bolivia

P. Jones 1*, Y. Arocha 2, O. Antezana 3, E. Montellano 3 and P. Franco 4

*phil.jones@bbsrc.ac.uk

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Accepted: 05 Nov 2004

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 ('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 (Fig. 1A&B). Tubers often produced hair-like shoots, reducing their quality and yield (Fig. 1C). Previously, this syndrome was presumed to be rhizoctoniosis, caused by basal stem infection by Rhizoctonia solani. However, R. solani was absent from all diseased plants examined in the present study.

As other potato diseases similar to brotes grandes (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 an unidentified vine with little-leaf symptoms (Fig. 2) 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 the unknown vine (Accession No. AY725210) were each most similar (98%) to that of ash witches' broom phytoplasma (Accession number AY568302). This is the first report of a phytoplasma of the Aster yellows (16SrI) group associated with a potato disease in Bolivia.

Figure1a+Figure1b+Figure1c+
Figure 1: Figure 1 (left to right): A & B, brotes grandes on intact and excised stems of potato. C, Hair-like shoots from tubers
Figure 1: Figure 1 (left to right): A & B, brotes grandes on intact and excised stems of potato. C, Hair-like shoots from tubers
Figure2+
Figure 2: Unknown vine with little-leaf symptoms.
Figure 2: Unknown vine with little-leaf symptoms.

Acknowledgements

Work in the UK was done under Defra plant health licence no. PHL 174B/4612(09/20003).

References

  1. Hamilton D, 2000. Potato Stolbur Phytoplasma in Poland. European and Mediterranean Plant Protection Organisation (EPPO) report (04).
  2. Harding RM, Teakle DS, 1993. Potato purple top wilt in Queensland. In: Raychaudhuri SP and Teakle DS, eds. Management of plant diseases caused by fastidious prokaryotes. New Delhi, India: Associated Publishing Co., 14-20.
  3. Khadhair A, Duplessis H, McAlister P, Ampong-Nyarko K, Bains P, 2003. Transmission and characterization of phytoplasma diseases associated with infected potato cultivars in Alberta. Acta Horticulturae 619,167-176.
  4. Martínez-Soriano JP, Leyva-López NE, Zavala-Soto ME, Bères M, Leal-Klevezas DS, 1999. Detección molecular del agente causal del síndrome "bola de hilo" de la papa en semillas infectadas y asintomáticas. Biotecnología Aplicada 16, 93-96.
This report was formally published in Plant Pathology

©2004 The Authors