November 25, 2004
Source: British Soc. Plant Pathol., New Disease Reports, Vol. 10 [edited]

Hoja de perejil (parsley leaf) of tomato and Calotropis little leaf, 2 new diseases associated with a phytoplasma in Bolivia
P. Jones, Plant-Pathogen Interactions Division, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK; Y. Arocha, National Center for Animal and Plant Health (CENSA), Apdo 10, San Jose de Las Lajas, Havana, Cuba; O. Antezana, Ladiplantas Community Plant Clinic, Comarapa, Bolivia; E. Montellano (as for Antezana); and P. Franco, CIAT, Santa Cruz, Bolivia. Accepted for publication 06/10/04

Tomatoes (_Lycopersicon esculentum_), an important cash crop for smallholder farmers in the hillside production systems of the Valles crucenos, 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. Infected 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 _Calotropis_ sp. (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 _Calotropis_ plants with little-leaf. SR sequences
from hoja de perejil (GenBank Accession No. AY725208) and Calotropis little leaf (No. AY725207) were compared with those of other phytoplasmas in GenBank using BLAST. They showed a maximum (91 percent) homology with phytoplasmas from the 16SrI Aster yellows group.

This is the 1st report of hoja de perejil disease of tomato, where infection rates of over 60 percent were seen in some fields of the most popular cultivar 'Rio Grande'. This is also the first report of Calotropis 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.

References

Deng S, Hiruki D, 1991. Amplification of 16S rRNA genes from culturable and nonculturable mollicutes. Journal of Microbiological Methods 14, 53-61.

Gundersen DE, Lee IM, 1996. Ultrasensitive detection of phytoplasmas by nested-PCR assays using two universal primer pairs. Phytopathologia Mediterranea 35, 144-51.

Schneider B, Seemuller E, Smart C, Kirkpatrick BC, 1995. Phylogenetic classification of plant pathogenic mycoplasmalike organisms or phytoplasmas. In: Razin R, Tully JG, eds. Molecular and Diagnostic Procedures in
Mycoplasmology, Vol I, San Diego, USA: Academic Press, 369-80.

Smart CD, Schneider B, Blomquist CL, Guerra LJ, Harrison NA, Ahrens U, Lorenz KH, Seemuller E, Kirkpatrick BC, 1996. Phytoplasma-specific primers based on sequences of the 16S-23S rRNA spacer region. Applied and
Environmental Microbiology 62, 2988-93.

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[The gist of this piece is that a possibly new 16Sr phytoplasma subgroup has emerged in the tomato cv 'Rio Grande' and in _Morrenia variegata_ [Mv] in the Bolivian provinces of Santa Cruz and Sucre. An infection rate of 60 percent suggests that the disease may be widespread in some areas, but there are no data on crop loss in tomato. Obviously the phytoplasma is well- established in Mv in affected areas of Bolivia and constitutes a source of inoculum.

Incidentally, I could not find Mv among several data bases, only _M. odorata_ (latex plant). Perhaps our colleagues can provide the correct species name.

Link:
<http://www.bspp.org.uk/ndr/jan2005/withheld2004-59.temp>
- Mod.DH]