Potential Weed Species as Alternate Hosts of Insect Vectors of the Lethal Yellowing Disease (LYD) of Coconut Palms (Cocos nucifera L.) in Nigeria

<p>The genetic diversity of Cocos nucifera L. is described, based on historical, and ethnobotanical studies and it is evaluated by analyzing patterns of morphological variation of fruit, variation in morpho-physiology of plants and leaves, and iso-enzyme polymorphism. Genetic structure of populations was analyzed and evaluated in relation with Lethal Yellowing disease for seven years. The diversity includes four ecotypes of tall coconut: 'Atlantic Tall', 'Pacific Tall l ', Pacific Tall 2', and 'Pacific Tall 3', and one ecotype of dwarf coconut: 'Malayan Dwarf'. Results suggest several early introductions of tall ecotypes to Mexico that were already differentiated. The genetic distance observed between Mexican populations and recently imported ecotypes suggest that the 'Atlantic Tall' originated from the west coast of Africa, while the 'Pacific Tall' ecotypes originated in the Pacific Islands, the 'Malayan Dwarf' ecotype provenances from South-East Asia. Levels of diversity in the Mexican population were similar to those of the area of New Guinea and to the collection of<br />the Ivory Coast. The diversity found was exposed to Lethal Yellowing disease over a period of seven years. The 'Atlantic Tall' ecotype showed a high susceptibility, the 'Pacific Tall 3' medium susceptibility, the Pacific Tall 1 and 'Pacific Tall 2' medium resistance while the 'Malayan Dwarf' showed high resistance. It is necessary to implement a program of conservation for the ecotypes 'Atlantic Tall' and 'Pacific Tall 3', and to initiate a breeding program of crosses between 'Pacific Tall 2' with 'Malayan Dwarf' aimed at obtaining genotypes<br />resistant to Lethal Yellowing disease which will increase productivity.</p>

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First Report of Lethal Yellowing Disease of Coconut Palms Caused by Phytoplasma on Nevis Island

Plant Disease ◽

10.1094/pd-90-0834a ◽

2006 ◽

Vol 90 (6) ◽

pp. 834-834 ◽

Cited By ~ 6

Author(s):

W. A. Myrie ◽

L. Paulraj ◽

M. Dollet ◽

D. Wray ◽

B. O. Been ◽

...

Keyword(s):

Cocos Nucifera ◽

Universal Primer ◽

Cayman Island ◽

First Report ◽

Lethal Yellowing Disease ◽

Immature Leaf ◽

Palm Species ◽

Lethal Yellowing ◽

Healthy Control ◽

Yellowing Disease

Coconuts (Cocos nucifera) are an important small-holder's crop in many tropical countries and are used to enhance esthetics of coastal areas. Lethal yellowing (LY) is the single most important plant disease affecting the coconut industry in Jamaica. It affects many palm species in Jamaica, Florida, and Guatemala. This coconut disease was first recorded in Grand Cayman Island in 1834 and Jamaica in 1884. Symptoms of LY disease include premature nut fall, necrosis of the inflorescence, yellowing of the leaves, and defoliation. Thirty-eight coconut palms displaying symptoms indicative of LY disease were sampled in April, 2005 at several locations in Nevis. Immature leaf tissues (leaf bases adjacent to the apical meristem) and nondestructive (boring with a bit and braces) samples were collected from disease and healthy control coconut trees. DNA was extracted (2). The first round of polymerase chain reaction (PCR) with phytoplasma universal primer pair P1/P7 (1,3) resulted in an rDNA fragment of 1.8 kb, and a subsequent nested PCR using LY16-23Sr/LY16Sf primers yielded an amplicon of 1.74 kb (4). Purified product was cloned for sequencing. Sequences obtained were analyzed with Vector NTI Software Suite. The sequence of LYN 18-3 was entered in Genbank and Accession No. DQ378279 was assigned. LYN 18-3 has approximately 99% homology with LY Phytoplasma U18747 from Florida (Manila palm [Veitchia merrillii]). The disease-associated phytoplasma was reliably detected in immature tissues and trunk phloem at the onset of foliar symptoms in palms by PCR. On the basis of the results obtained from this study, it is clear that LY phytoplasma (16SrIV group) was found in the samples collected from Nevis. To our knowledge, this is the first report on lethal yellowing disease in Nevis. References: (1) S. Deng and C. Hiruki. J. Microbiol. Methods 14:53 1991. (2) J. J. Doyle and J. L. Doyle. Focus 12:13, 1990. (3) N. A. Harrison et al. Ann. Appl. Biol. 141:183, 2002. (4) C. D. Smart et al. Appl. Environ. Microbiol. 62:2988, 1996.

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First Report of Lethal Yellowing Group (16Sr IV) of Phytoplasmas in Vernonia cinerea in Jamaica

Plant Disease ◽

10.1094/pdis-92-7-1132a ◽

2008 ◽

Vol 92 (7) ◽

pp. 1132-1132 ◽

Cited By ~ 5

Author(s):

S. E. Brown ◽

B. O. Been ◽

W. A. McLaughlin

Keyword(s):

Cocos Nucifera ◽

Coconut Palm ◽

Weed Species ◽

First Report ◽

Representative Sequence ◽

Pcr Products ◽

Lethal Yellowing ◽

Vector Identity ◽

Cocos Nucifera L ◽

Vernonia Cinerea

Coconut lethal yellowing disease (CLY) has had a devastating effect on the coconut (Cocos nucifera L.) industry in Jamaica and Latin America. A study was conducted in Jamaica during 2005 to identify alternate hosts of the CLY phytoplasma. Since weeds are known to act as reservoir hosts of numerous pathogens, Vernonia cinerea (L.) (Asteraceae), a prevalent weed species on coconut farms island-wide, was collected from coconut farms in areas of high and low levels of CLY incidence, although none of the plants displayed disease symptoms. DNA was extracted from plant samples by the method of Dellaporta et al. (1) and analyzed by nested PCR assay employing phytoplasma universal rRNA operon primers P1/P7 (2,4) and LY16Sf/LY16-23Sr (3). DNA derived from CLY-diseased or healthy coconut palm served as positive and negative controls, respectively, in each assay. Amplification of an rDNA product of the expected size (1.7 kb) confirmed phytoplasma infections in 53 of 118 (44.9%) V. cinerea test plants. Twenty-seven of the rDNA PCR products were analyzed by digestion with restriction enducleases RsaI, MspI, MseI, TaqI, HinfI, and HhaI. The restriction fragment length polymorphism profiles obtained were similar to that observed in the CLY-infected coconut palm. V. cinerea rDNA amplicons were cloned and sequenced (in both directions) and a representative sequence was deposited in GenBank (Accession No. EU057983). Blast analysis determined this sequence to be most similar (99%) to that of CLY phytoplasma in Jamaica (Accession No. AF49807) and Florida (Accession No. AF498309). To our knowledge, this is the first report of the 16Sr IV group of phytoplasmas infecting V. cinerea. Presence of the lethal yellowing phytoplasmas in dicotyledonous plant species has important epidemiological implications concerning vector identity and ecology. Futhermore, it is now evident that weed control on coconut farms could assist in the management of CLY disease in Jamaica. References: (1) S. L. Dellaporta et al. Plant Mol. Biol. Rep. 1:19, 1993. (2) S. Deng and C. Hiruki. J. Microbiol. Methods 14:53, 1991. (3) N. A. Harrison et al. Ann. Appl. Biol. 141:183, 2002. (4) C. D. Smart et al. Appl. Environ. Microbiol. 62:2988, 1996.

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