Occurrence of a Clover Proliferation (16SrVI) Group Phytoplasma Associated with Little Leaf Disease of <i>Portulaca grandiflora</i> in India
Bibliographic record
Abstract
Portulaca grandiflora (family Portulacaceae), commonly known as moss rose purslane, is a popular ornamental plant widely grown in temperate climates because it blooms all summer. Portulaca is also used for medicinal purposes since it is rich in vitamins A, B1, and C and has antimicrobial and cytotoxic activity. Since March 2005, 30 to 50% of P. grandiflora plants in the ornamental gardens as well as in pots at the Central Institute of Medicinal and Aromatic Plants, Lucknow, India have displayed symptoms resembling phytoplasma infection. Disease symptoms start as a typical bud proliferation, downward curling, and diminishing size of leaves, followed by overall stunted growth and yellowing of the whole plant from April to June. Some plants also formed rosettes and a proliferation of axillary shoots resulting in a witches'-broom appearance. Typical pleomorphic bodies, mostly spherical to oval, ranging from 340 to 1,100 nm were observed only in sieve elements of infected plants by transmission electron microscopy (TEM). On the basis of symptoms, TEM observations, PCR, and response to antibiotic treatment, the causal organism was identified as phytoplasma (1). Total genomic DNA from healthy and infected plants was extracted with the CTAB buffer method (2). Of 27 suspected samples screened by PCR, 23 were phytoplasma positive. Presence of phytoplasmas in plants was demonstrated by a nested PCR assay employing primer pair P1/P6 followed by R16F2n/R16R2 that generated rDNA products of 1.5 and 1.2 kb, respectively, only from symptomatic plants. No differences among phytoplasmas in Portulaca plants were detected by restriction fragment length polymorphism (RFLP) analysis of nested rDNA (1.2 kb) products using endonucleases BamHI, RsaI, AluI, HpaII, and EcoRI. Comparative analysis of RFLP patterns with those derived from reference phytoplasmas tentatively identified the Portulaca little leaf (PLL) phytoplasma as a member of 16S rDNA RFLP group 16SrVI (3). A nested PCR product (1.25 kb) was cloned with a TOPO TA cloning kit (Invitrogen, Carlsbad, CA) and sequenced. The sequence was deposited in the GenBank database (Accession No. EF651786). Sequence analysis revealed the PLL phytoplasma to be most similar (98%) to Indian brinjal little leaf (Accession No. EF186820) and 'Candidatus Phytoplasma trifolii' (Accession No. AY390261), two 16SrVI group phytoplasmas previously reported from India and Canada, respectively. The status of PLL (EF651786) was also verified by in silico RFLP analysis (4) of the F2n/R2 sequence of six closely related strains (Accession Nos. AF228052, AY390261, AY270156, AY409070, AY409069, and EF186820) of the 16SrVI group using 17 restriction enzymes (AluI, BamHI, BfaI, BsfUI, DraI, EcoRI, HaeIII, HhaI, HinfI, HpaI, HpaII, KpnI, MseI, Sau3AI, RsaI, SspI, and TaqI). In silico restriction digestion and virtual gel plotting showed similar patterns for all enzymes. To our knowledge, this is the first report of a 16SrVI group phytoplasma infecting Portulaca plants in India. References: (1) P. V. Ajayakumar et al. Aust. Plant Dis. Notes 2:67, 2007. (2) S. P. S. Khanuja et al. Plant Mol. Biol. Rep. 17:74, 1999. (3) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (4) W. Wei et al. Int. J. Syst. Evol. Mic. 57:1855, 2007.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".