Search for alternate hosts of the coconut Cape St. Paul Wilt disease pathogen

Le jaunissement mortel, localement appelé Cape Saint Paul Wilt Disease (CSPW), est le fléau de l'industrie du cocotier au Ghana et est causé par un phytoplasme. Au Ghana existe des endroits ou la maladie est réapparue sur des replantations longtemps après qu'elle y ait décimé l'ensemble des cocotiers. Ceci suppose la possibilité d'hôtes alternatifs qui participeraient à la propagation de la maladie, puisque l'agent pathogène est un parasite obligatoire. Pour ces travaux, de nombreuses plantes ont été testées pour leur statut d'hôte au CSPW. La présence de phytoplasmes dans ces plantes a été testée par analyse PCR en utilisant les amorces spécifiques des phytoplasmas P1/P7, et les amorces spécifiques du CSPWD G813/GAKSR. L'identification d'hôte alternatif pourra nous aider à définir des stratégies de contrôle contre la dispersion de la maladie. (Résumé d'auteur

Search for alternate hosts of the coconut Cape Saint Paul Wilt Disease pathogen

Lethal Yellowing disease locally called Cape Saint Paul wilt disease (CSPWD) is the bane of the coconut industry in Ghana and is caused by a phytoplasma. In Ghana, there are areas where the disease has re-infected re-plantings long after decimating all the palms in the area. This brings to the fore the possibility of alternate hosts in the spread of the disease because the pathogen is an obligate parasite. In this work, a number of plants were screened for their host status to the CSPWD pathogen. The presence of phytoplasmas in these plants was tested by polymerase chain reaction analysis using universal phytoplasma primers P1/P7 and CSPWD-specific primers G813/GAKSR. Although Desmodium adscendens tested positive to the CSPWD-specific primers, cloning and sequencing did not confirm it as an alternate host. The identification of alternate hosts will help us to evolve sound control strategies against the spread of the disease. (Résumé d'auteur

Molecular identification of ‘Candidatus Phytoplasma palmicola’ associated with coconut lethal yellowing in Equatorial Guinea

During the past two decades, a high mortality of coconut palms was observed in the coastal areas of Equatorial Guinea. Reportedly, the palm population has been reduced by 60%-70%, and coconut production has decreased accordingly. To identify the cause of the mortality, a survey was carried out in April 2021 in various localities of the coconut belt. Molecular analyses carried out on 16S rRNA and secA genes detected phytoplasma presence in the majority of the samples. Sequencing and BLAST search of the 16S rRNA gene sequences showed >99% identity of the detected phytoplasmas to 'Candidatus Phytoplasma palmicola'. The RFLP analyses of 16S ribosomal gene using Tru1I and TaqI enzymes led to assign these phytoplasmas to subgroup 16SrXXII-A. In all samples that tested positive, including one from a hybrid coconut palm and two from oil palm the same phytoplasma was identified. The phylogenetic analyses of 16S rRNA and secA genes confirmed respectively 99.98%-100% and 97.94%-100% identity to 'Ca. P. palmicola'. RFLP analyses using MboII enzyme on the secA gene amplicon differentiated the phytoplasma found in Equatorial Guinea from those present in Ghana and Ivory Coast. The Equatorial Guinean phytoplasma strain resulted to be identical to the strains from Mozambique, confirming the presence of a geographic differentiation among phytoplasma strains in the coastal areas of Western and Central Africa. The identified phytoplasma is different from the 'Ca. P. palmicola' strains found in Ghana and Ivory Coast and represents the first identification a 16SrXXII-A strain in Equatorial Guinea and in Central Africa. Strict monitoring and surveillance procedures for early detection of the pathogen are strongly recommended to reduce its impact and further spread in the country and permit the recovery of coconut plantations

Evaluation of some basic traits of a promising coconut hybrid: Sri Lankan green dwarf crossed to Vanuatu tall (sgd x vtt)

The Lethal Yellowing Disease locally referred to as the “Cape St Paul Wilt Disease” is the single most important disease that has devastated several hectares of coconut plantations in Ghana. Two decades of coconut screening for tolerant planting material has identified the Sri LankanGreen Dwarf crossed Vanuatu Tall (SGD x VTT) coconut hybrid as the most promising planting material in the context of disease. To provide farmers with planting material that has high disease tolerance and also good agronomic characteristics, the study compared some basic traits ofthe coconut hybrid with other important coconut varieties with the objective of determining the suitability of the SGD x VTT as alternative planting material to revamp the coconut industry in Ghana. Mean sample size of 25 palms per coconut variety under the study was analyzed using two sample t-test procedure. The study indicated that the yield performance of the SGD x VTT coconut hybrid was better than the tall coconut types including the local West African Tall (WAT) and compared favourably with the Malayan Yellow Dwarf crossed Vanuatu Tall (MYD x VTT) coconut hybrid. The good agronomic characteristics of the SGD x VTT coupled with itshigh resistance to the CSPWD proved its suitability as alternative planting material to revamp the coconut industry in Ghana

Resistance screening trials on coconut varieties to Cape Saint Paul Wilt in Ghana

La maladie du cocotier de Cap Saint Paul (CSPWD), signalée pour la première fois au Ghana en 1932, est une maladie du type jaunissement mortel. C'est la plus sérieuse menace pour le cocotier dans le pays. La stratégie de lutte recommandée dans le monde est la culture de variétés de cocotier résistantes à la maladie. Plus de 38 variétés ont été éprouvées depuis 1956 pour leur résistance au CSPWD et les résultats sont mentionnés dans cet article. Deux variétés, le Nain vert de Sri Lanka (NVS) et le Grand du Vanuatu (GVT), ont montré une grande résistance à la maladie, et les caractéristiques agronomiques de leur hybride SGD x VTT sont en cours d'évaluation. Un programme de replantation des zones dévastées par la maladie a débuté en 1999. Il est apparu que l'hybride MYD x VTT utilisé dans ce programme, a été infecté suite à une forte pression de la maladie. Une nouvelle orientation du programme de replantation et la sélection d'autres variétés ont été recommandées. Mots clés: Ghana, maladie de Cap St. Paul, cocotier, variétés, résistance. (Résumé d'auteur

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder