Phytoplasma diseases of date palm in Northern Sudan
Palms have not been reported to be affected by phytoplasma diseases in the EPPO region, and palm lethal yellowing phytoplasma is an A1 quarantine pest for EPPO. A new disease of young date palms, known as white tip die-back, has recently been identified in northern Sudan (Cronjé et al., 2000a). It causes severe chlorosis of the emerging spear leaf and chlorotic streaking of the fronds. The young palms die within 6-12 months of symptom appearance. Use of a nested PCR test showed that phytoplasma-specific products could consistently be amplified from affected palms; but not from healthy ones. The product had a high homology with comparable sequences of Bermuda grass white leaf phytoplasma.
It has also been shown (separate report by Cronjé et al., 2000b) that slow decline of mature date palms, a disease of uncertain etiology already known for a long time in northern Sudan and characterized by progressive yellowing and shedding of the fronds leading to death (causing an annual loss of 6%), gives the same test result as above, so that both diseases are very probably caused by the same phytoplasma.
There is thus a probable phytoplasma disease of date palm in northern Africa, which may present a phytosanitary risk to the EPPO countries where date palm is cultivated, and more generally to ornamental palms in the southern part of the EPPO region. The phytoplasma involved may be Bermuda grass white leaf phytoplasma. This pathogen has been reported from at least Pakistan, Taiwan and Thailand. Recently, Marcone et al. (1997) have reported it from Cynodon dactylon (Bermuda grass) in Italy, while Lee et al. (1997) have reported a very closely related phytoplasma from Poa annua in Italy. These reports are the first in the EPPO region, but it is not clear that the world distribution of this phytoplasma is adequately known. Cronjé et al. incidentally mention a Sudanese isolate, presumably from C. dactylon.
Cronjé et al. (2000a, b). New Disease Reports Vol 1, http:///www.bspp.org.uk/ndr
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