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Phytoplasma host range and symptom expression in the pasture legume Stylosanthes

De La Rue, Stephanie J., Hopkinson, Lance, Foster, S. and Gibb, Karen S. (2003). Phytoplasma host range and symptom expression in the pasture legume Stylosanthes. Field Crops Research,84(3):327-334.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 6 times in Scopus Article | Citations

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Title Phytoplasma host range and symptom expression in the pasture legume Stylosanthes
Author De La Rue, Stephanie J.
Hopkinson, Lance
Foster, S.
Gibb, Karen S.
Journal Name Field Crops Research
Publication Date 2003
Volume Number 84
Issue Number 3
ISSN 0378-4290   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-0344736652
Start Page 327
End Page 334
Total Pages 8
Place of Publication Milnthorpe, Cumbria, UK
Publisher Elsevier
Field of Research 0607 - Plant Biology
0703 - Crop and Pasture Production
HERDC Category C1 - Journal Article (DEST)
Abstract A field trial of 23 stylo taxa was assessed for susceptibility to stylosanthes little leaf (SLL) disease. The trial included Stylosanthes scabra cvv. Seca, Siran, and Fitzroy, S. guianensis var. guianensis cv. Cook, S. hamata cvv. Amiga and Verano and Stylosanthes seabrana cvv. Unica and Primar, as well as seven unreleased cultivars from a CSIRO anthracnose resistance breeding program, and four unreleased introduced lines. Plants that had SLL symptoms were sampled on six occasions from March to August 1999 and tested for phytoplasmas, the presumed causal organism of this disease, using the polymerase chain reaction (PCR). All taxa were found to be susceptible to SLL disease except S. hamata cv. Verano and S. seabrana cv. Unica. Varieties were ranked on disease incidence, with S. scabra varieties bred for anthracnose resistance having the highest incidence of the disease. These varieties also had significantly higher SLL incidence than that of the original introductions from which they were derived. Before testing, symptom profiles were recorded noting the presence of chlorosis, spike elongation, reddening of leaf tips and floral parts, and reduced leaf size (little leaf). Statistical analysis of the association of these characteristics with SLL disease showed that little leaf was the best disease indicator and that chlorosis and excessive reddening of leaf tips and floral parts were also associated with the disease. The presence of floral abnormalities was also recorded in the symptom profiles. At no time were normal flowers found on samples that had SLL, making this symptom a good indicator of SLL. However, not all plants with floral symptoms tested positive for phytoplasmas by PCR, probably because these symptoms are difficult to diagnose visually. Virescence and phyllody were the most common floral abnormalities and were found to be associated specifically with the phytoplasmas pigeon pea little leaf and sweet potato little leaf variant V4, respectively. An additional floral abnormality, termed abortion, was also observed in association with this disease.
Keywords phytoplasma
dna extraction
leaf phytoplasma
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