Characterisation and control of Curvularia lunata infecting farmer-saved rice seeds in Ghana

Curvularia species are increasingly important seed-borne fungi, whose identification has been done based solely on cultural and morphological features in Ghana. To confirm the identity of the fungus in Ghana, isolates of the fungus obtained from farmer-saved rice seeds were identified using cultural and morphological features, complemented with phylogenetic analysis of the internal transcribed spacer regions of isolates. The susceptibility of isolates to three plant based fungicides, Levo, Kobe and Ex-icute was determined with in-vitro and in-vivo. All isolates produced curved shaped spores with several septations. In the phylogram, they all clustered in the C. lunata clade, confirming their C. lunata species status. All isolates were susceptible to the three organic fungicides and seeds treated with the three fungicides reduced fungal infection percentage. For safer environmental practices, these plant based fungicides are recommended for rice seed treatment

Importance of the onion leaf twister disease in Ghana and the effect of Trichoderma asperellium on the mycelial growth and sporulation of the causal agent

Abstract Studies were carried out to determine the disease incidence and severity of the onion leaf twister disease in the Eastern Region of Ghana to confirm the aetiology of the disease in the country. Field survey was carried out in two districts of the Eastern Region and the disease incidence and severity were measured. The causal agent was isolated on media and identified using morphological characteristics, and polymerase chain reaction with the species specific primer CgInt combined with ITS4 primer. The effect of Trichoderma asperellium on the mycelial growth and sporulation of the causal agent of the disease were determined. The results showed that the disease incidence was 43.6 per cent and 62.5 per cent in the Kwahu South and Fanteakwa districts, respectively, with severity of 0.8 and 2.7 respectively, on a scale of 1 – 5. The causal agent was confirmed as Colletotrichum gloeosporioides. The bio-agent, T. asperellium was able to significantly suppress the mycelial growth and sporulation of the pathogen infecting the onions

Management of Lasiodiplodia theobromae , the causal agent of mango tree decline disease in Ghana

Mango ( Mangifera indica L.), is one of the economically most important crops in Ghana. It is recognised for its popularity in contributing to food and nutritional security. Despite its economic importance, mango tree decline disease, caused by Lasiodiplodia theobromae, poses a serious threat to the mango industry in the country. The objective of this study was to evaluate fungicides (i.e., carbendazim, zamir, mancozeb, funguran and sulphur 80) and bio pesticides ( Chromolaena odorata , Azadirachta indica and Carica papaya ) against L. theobromae. The results showed that all the tested fungicides, except for sulphur 80, inhibited mycelial radial growth of L. theobromae, with carbendazim and funguran improving the vegetative growth of the shoots and leaves in the field. Mango trees treated with carbendazim, after the third spray, had no disease symptoms. However, application of urea fertiliser and carbendazim (50 g 15 L-1 water), at a two-week spraying interval in the field, reduced the severity of L. theobromae. Application of biopesticides (plant extracts) showed that C. odorata had the highest efficacy, followed by A. indica and then C. papaya. Although further studies on plant extracts in the field are required, our findings provide important information for the development of integrated management strategies for the pathogen, and the disease it transmits.La mangue ( Mangifera indica L.) est l\u2019une des cultures les plus importantes \ue9conomiquement au Ghana. Il est reconnu pour sa popularit\ue9 en contribuant \ue0 la s\ue9curit\ue9 alimentaire et nutritionnelle. Malgr\ue9 son importance \ue9conomique, la maladie du d\ue9clin du manguier, caus\ue9e par Lasiodiplodia theobromae , constitue une menace s\ue9rieuse pour l\u2019industrie de la mangue dans le pays. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer les fongicides (c\u2019est-\ue0-dire le carbendazime, le zamir, le mancoz\ue8be, le fonguran et le soufre 80) et les pesticides biologiques ( Chromolaena odorata , Azadirachta indica et Carica papaya ) contre L. theobromae. Les r\ue9sultats ont montr\ue9 que tous les fongicides test\ue9s, \ue0 l\u2019exception du soufre 80, inhibaient la croissance radiale myc\ue9lienne de L. theobromae, le carbendazime et le fonguran am\ue9liorant la croissance v\ue9g\ue9tative des pousses et des feuilles au champ. Les manguiers trait\ue9s au carbendazime apr\ue8s la troisi\ue8me pulv\ue9risation ne pr\ue9sentaient aucun sympt\uf4me de maladie. Cependant, l\u2019application d\u2019engrais \ue0 base d\u2019ur\ue9e et de carbendazime (50 g 15 L-1 d\u2019eau) \ue0 un intervalle de pulv\ue9risation de deux semaines dans le champ a r\ue9duit la gravit\ue9 de L. theobromae. L\u2019application de biopesticides (extraits de plantes) a montr\ue9 que C. odorata avait la plus grande efficacit\ue9, suivie par A. indica et ensuite C. papaya. Bien que des \ue9tudes suppl\ue9mentaires sur les extraits de plantes sur le terrain soient n\ue9cessaires, nos r\ue9sultats fournissent des informations importantes pour le d\ue9veloppement de strat\ue9gies de gestion int\ue9gr\ue9e du pathog\ue8ne et de la maladie qu\u2019il transmet

PREVALENCE OF PLANT-PARASITIC NEMATODES IN RICE FIELDS IN GHANA

Rice ( Oryza sativa L.) is one of the most cultivated crops worldwide whose production in sub-Saharan Africa is extensively affected by root nematodes. The objective of this study was to identify and establish the distribution of plant-parasitic nematodes (PPNs), in rice growing fields within different regions of Ghana. Soil and root samples were taken from rice fields, namely fourteen from Volta Region, eleven from the Soil and Irrigation Research Centre (SIREC), Kpong (Eastern Region); and five from Dawhenya (Greater Accra Region). The soil samples were taken from 0-30 cm depths, together with root samples. A total of twenty-four nematode genera were identified in soil and root samples from the three regions. These included: Aphelenchus spp., Belonolaimus spp., Ditylenchus spp., Dolichodorus spp., Helicotylenchus spp., Hemicriconemoides spp. Hemicycliophora spp. Heterodera spp., Hirschmaniella spp., Hoplolaimus spp., Longidorus spp., Meloidogyne spp., Paralongidorous spp., Paratylenchus spp., Pratylenchus spp., Radopholus spp., Rhabditida spp., Rotylenchulus spp., Scutellonema spp., Trichodorus spp., Tylenchornchus spp., Tylenchulus spp., Tylenchus spp. and Xiphinema spp. In the Volta Region, Tylenchus spp. was the most abundant (29.01%) in the soil; while Meloidogyne spp. was most the abundant (36.86%) in the roots. In Dawhenya regions, Meloidogyne spp. was the most abundant (26.96%) in the soil; while Tylenchus spp. was the most abundant (25.94%) in the roots. In the Eastern Region, Meloidogyne spp. was the most abundant (41.7%) in the soil; while Pratylenchus spp. was the most abundant (36.1%) in the roots. These nematodes threaten rice production in Ghana, if not managed well in farmer\u2019s fields.Le riz ( Oryza sativa L.) est l\u2019une des cultures les plus cultiv\ue9es au monde dont la production en Afrique subsaharienne est largement affect\ue9e par les n\ue9matodes des racines. L\u2019objectif de cette \ue9tude \ue9tait d\u2019identifier et d\u2019\ue9tablir la r\ue9partition des n\ue9matodes phytoparasites (NPP) dans les rizi\ue8res de diff\ue9rentes r\ue9gions du Ghana. Des \ue9chantillons de sol et de racines ont \ue9t\ue9 pr\ue9lev\ue9s dans les rizi\ue8res, \ue0 savoir quatorze de la r\ue9gion de la Volta, onze du Centre de Recherche sur les Sols et l\u2019Irrigation (SIREC), Kpong (r\ue9gion de l\u2019Est)\ua0; et cinq de Dawhenya (r\ue9gion du Grand Accra). Les \ue9chantillons de sol ont \ue9t\ue9 pr\ue9lev\ue9s \ue0 des profondeurs de 0 \ue0 30 cm, ainsi que des \ue9chantillons de racines. Au total, vingt-quatre genres de n\ue9matodes ont \ue9t\ue9 identifi\ue9s dans des \ue9chantillons de sol et de racines des trois r\ue9gions. Ceux-ci comprenaient : Aphelenchus spp., Belonolaimus spp., Ditylenchus spp., Dolichodorus spp., Helicotylenchus spp., Hemicriconemoides spp. Hemicycliophora spp. Heterodera spp., Hirschmaniella spp., Hoplolaimus spp., Longidorus spp., Meloidogyne spp., Paralongidorous spp., Paratylenchus spp., Pratylenchus spp., Radopholus spp., Rhabditida spp., T. ., Tylenchornchus spp., Tylenchulus spp., Tylenchus spp. et Xiphinema spp. Dans la r\ue9gion de la Volta, Tylenchus spp. \ue9tait le plus abondant (29,01 %) dans le sol; tandis que Meloidogyne spp. \ue9tait le plus abondant (36,86%) dans les racines. Dans les r\ue9gions de Dawhenya, Meloidogyne spp. \ue9tait le plus abondant (26,96 %) dans le sol; tandis que Tylenchus spp. \ue9tait le plus abondant (25,94 %) dans les racines. Dans la r\ue9gion orientale, Meloidogyne spp. \ue9tait le plus abondant (41,7%) dans le sol; tandis que Pratylenchus spp. \ue9tait le plus abondant (36,1 %) dans les racines. Ces n\ue9matodes menacent la production de riz au Ghana, s\u2019ils ne sont pas bien g\ue9r\ue9s dans les champs des agriculteurs

Incidence and Aetiology of Stem End Rot and Anthracnose Diseases Affecting Soursop Fruits at Pre-Harvest and Post-Harvest Stages in Ghana

Soursop is increasingly becoming an important fruit crop in Ghana especially within the urban areas. A research work was carried out to identify the major diseases and their associated pathogens affecting the crop at both the pre-harvest and post-harvest stages of fruits in the country. Diseased soursop fruits of the local varieties were collected from the coastal savannah zone of Ghana, disease symptoms expression on fruits studied and the causal agents identified using morphological and molecular approaches. Two major diseases namely, stem end rot and anthracnose were identified on the fruits. Cultural characteristics of isolates and the amplification of expected PCR products using species specific primers confirmed that Lasiodiplodia theobromae and Colletotrichum gloeosporioides were responsible for stem end rot and anthracnose diseases respectively. Mean disease incidences of stem end rot and anthracnose at the pre harvesting stage for a period of 3 years was 25.5% and 21.4% while at the post-harvest stage were 33.4% and 65.5% respectively. Though stem end rot was found to be more damaging as the fruits infected by the causal agent could not be utilized in any way, both diseases destroy the aesthetic and marketing values of the fruits and hence deserve attention. The information obtained in this study will be very useful for any future studies of the soursop crop in Ghana. Keywords: Soursop, Stem end rot, Anthracnose, Post-harvest RésuméSoursop est de plus en plus une culture fruitière importante au Ghana, en particulier dans les zones urbaines. Un travail de recherche a été effectué pour identifier les principales maladies et leurs pathogènes associés affectant la culture aux stades pré-récolte et post-récolte des fruits dans le pays. On a prélevé des fruits malades des variétés locales dans la savane côtière du Ghana, on a exprimé les symptômes de la maladie sur les fruits étudiés et on a identifié les agents causals à l'aide d'approches morphologiques et moléculaires. Deux grandes maladies, à savoir la pourriture des tiges et l'anthracnose, ont été identifiées sur les fruits. Les caractéristiques culturelles des isolats et l'amplification des produits de PCR attendus à l'aide d'amorces spécifiques à l'espèce ont confirmé que Lasiodiplodia theobromae et Colletotrichum gloeosporioides étaient responsables respectivement de la pourriture des tiges et de l'anthracnose. L'incidence moyenne de la pourriture terminale et de l'anthracnose avant la récolte pendant une période de trois ans était de 25,5 % et de 21,4 %, alors qu'elle était de 33,4 % et de 65,5 % respectivement après la récolte. Bien que la pourriture terminale de la tige se soit avérée plus dommageable que les fruits infectés par l'agent causal ne pouvaient être utilisés en aucune façon, les deux maladies détruisent les valeurs esthétiques et de commercialisation des fruits et méritent donc l'attention. Les renseignements obtenus dans le cadre de cette étude seront très utiles pour toute étude future de la culture de l'acide sulfurique. Mots clés: Soursop, pourriture des tiges, anthracnose, post-récolt