Evidence for the presence of greening disease of citrus in P. Malaysia
1990
Lim, W.H. (MARDI, Klang, Selangor (Malaysia)) | Ko, W.W. | Mohd Shamsuddin, O.
Greening disease of citrus has been suspected to be present in Malaysia for sometimes, based symptoms, but no evidence to confirm its presence has thus far been forwarded. This paper presents the evidence based on symptomatology, transmission studies and trunk injection (with antibiotics). Initial graft trasmission studies, done in Cameron Highlands were negative, due to the low temperature there (18 approximately 5 degree celsius). Similar studies done in the warmer lowland (Klang at 29 approximately 3 degree celsius) showed that the disease could be transmitted to healthy sweet orange (cv. Madam Vinous) by double chip grafting. Positive transmission was also obtained by caging the psyllid vector, Diaphorina citri with healthy Citrus seedlings. Studies to investigate disease transmission from diseased trees to healthy periwinkle (Catharanthus roseus) by dodder (Cuscuta campestris) is still in progress. Treatment of diseased trees with antibiotic (oxytetracycline) by trunk injection provided evidence as the decline of five of the seven treated trees was checked (compared with control); in some cases recovery was 50 percent better than the control trees. Final proof was obtained when Garnier and Bove observed the greening organism (GO) in diseased leaf samples from Malaysia. Malaysian samples of diseased leaves (with greening symptoms) and insect vectors were tested against monoclonal antibodies and hybridoma supernatants (2D12 and 10A6, developed from the Indian greening organism, Poona strain, obtained from INRA, Broudeaux, France) by the techniques of ELISA and immunofluorescence, respectively. The results showed that the Malaysian greening organisms, like those from Thailand and China, did not react with the monoclonal antibodies and hybridoma supernatants, indicating that the strains from those countries were distinct from the Indian (Poona) strain
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