Etiology of orange leaf [Philippines].
1985
Jonson G.B. | Sta Cruz F.L. | Hibino H.
Rice plants showing orange leaf-like symptoms were collected at six locations in the Philippines and tested for transmission by vectors and presence of disease agent. Recilia dorsalis nymphs were given 2 or 4 days acquisition access or disease source. Average 13 percent of the insects transmitted the disease agent with incubation period ranging from 15-33 days. The pathogen was persistent in the vector. About 10% of the infective insects were able to transmit the disease continuously until its death. Retention period ranged from 18-43 days. The incubation period in the plant was 10-28 days. In addition to symptoms reported for orange leaf, ragged and twisted leaves on inoculated seedlings were also observed. Infected seedlings died within 3-4 weeks from symptom appearance. Utrathin sections of leaf tissues were obtained from rice plants infected with each isolate and examined under the electron microscope. Mycoplasma-like organisms (MLO) were observed in sieve tubes of all samples. The MLO were bounded with a unit membrane and pleomorphic, 50-1100 nm in diameter. This indicates that the pathogen causing orange leaf in the Philippines is not a virus but most likely a MLO.
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