African Crop Science Journal

Développement de Helicoverpa armigera, Hübner, 1805 (Lepidoptera : Noctuidae) sur différentes variétés de cotonnier au Bénin

2025-01-10T14:18:06+00:00

Le coton (Gossypium hirsutum L.) est la première plante textile cultivée dans le monde et reste la principale culture d’exportation de la plupart des pays d’Afrique de l’Ouest. Les programmes d’amélioration variétale du cotonnier devraient privilégier la production de variétés de fibres de haute qualité, multirésistantes aux adversités biotiques et abiotiques. Pour réduire l’impact des ravageurs sur le cotonnier, il est donc fondamental de sélectionner des variétés moins sensibles aux ravageurs et aux maladies. L’objectif de cette étude était d’identifier des variétés de cotonnier dotées d’une résistance à l’infestation de Helicoverpa armigera dans des conditions agro-écologiques béninoises. Une étude au laboratoire, portant sur quatre variétés de cotonnier (ANG 956, OKP768, KET782 et R663-4), a été menée. Les paramètres évalués comprenaient le nombre de chenilles de H. armigera qui ont survécu sur les cotonniers, la durée des chenilles jusqu’au stade L5, leur poids et leur taille, la durée d’apparition des chrysalides et leur poids, et la durée de l’émergence des papillons. Sur les quatre variétés testées, le stade L5 de H. armigera a été observé au 10ème jour. D’autre part, le temps de formation des chrysalides était le plus long dans la variété ANG 956, étant deux fois plus long que pour les autres variétés (KET 782, OKP 768 et R663-4). L’émergence des adultes a été plus longue dans la variété ANG 956, et plus courte dans les variétés KET 782, OKP 768 et R663-4. Helicoverpa armigera se développe mieux sur les variétés KET 782, OKP 768 et R663-4 que sur l’ANG 956, qui était plus résistant.

Qualité et capacité de charge des pâturages périurbains de la zone Sud-Soudanienne de la Cote d’Ivoire

2025-01-10T14:29:14+00:00

La production et la disponibilité de pâturages de haute qualité sont impératives pour garantir une production animale durable dans les zones urbaines et périurbaines. L’objectif de cette étude était d’évaluer la qualité et la capacité de charge des pâturages urbains et périurbains de Bouaké en Côte d’Ivoire. Un relevé floristique a été réalisé sur le couvert herbacé de Bouaké. Les données ont été collectées et utilisées pour calculer l’indice global de qualité des pâturages, également appelé valeur pastorale. La productivité fourragère potentielle des différents pâturages a été évaluée, selon la méthode de Fauche Intégrale qui a permis d’estimer les capacités de charge annuelles de ces pâturages. Au total, 106 espèces végétales réparties en 70 genres et 15 familles botaniques ont été recensées. Les valeurs pastorales obtenues (56,83 ± 1,15 et 61,37 ± 0,97 %) étaient inférieures à celles d’un pâturage en bon état (65-100 %). Les productivités potentielles de ces pâturages variaient de 0,94 ± 0,17 à 3,96±0,6 tonnes métriques de matière sèche par hectare par an (t MS ha-1.an-1), correspondant ainsi à des capacités de charge de 0,14±0,03-0,58 ±0,09 Unité Bétail Tropical par hectare par an (UBT ha-1. an-1), bien inférieures aux capacités de charge des pâturages sous de bonnes conditions (0,6 à 0,86 UBT ha-1.an-1) en Afrique de l’Ouest. Ces résultats démontrent l’ampleur de la dégradation des pâturages périurbains dans la zone sud soudanienne de la Côte d’Ivoire, suggérant le besoin urgent de prendre des mesures pour améliorer la qualité des pâturages et la capacité de charge du bétail.

Evaluation of genetic diversity in agronomic traits among dual-purpose cowpea genotypes in Kenya

2025-01-10T14:38:26+00:00

Availability of diverse genetic materials is central in any plant breeding programme. Genetic diversity is important in ensuring survival of a species; and buffering of crops from climate change effects through crop improvement programmes. The objective of this study was to determine the genetic diversity among a panel of dual purpose cowpea (Vigna unguiculata L.) genotypes to inform crop breeding programmes in Kenya. The study was conducted at the Jomo Kenyata University of Agriculture and Technology (JKUAT) Demonstration Farm in Kenya; during four cropping seasons (2021-2022). A total of 224 dual-purpose cowpea (Vigna unguiculata L.) genotypes were evaluated using an alpha lattice design with two replications. Data were recorded on agronomic traits, and were subsequently subjected to correlation and principal component analysis (PCA), biplot and hierarchical cluster analyses. Total grain yields positively correlated (P<0.05) with grain yield per row and pods plant-1. Principal component analysis dissected total variation into three components, namely PC1, PC2 and PC3. The first three PCs (with eigenvalues >1), accounted for 71.6% of the total variability among the accessions. PCA and Bi-plots showed that pods plant-1, grain yield plant-1 and per row were the best (farthest from the origin indicating largest divulgence) agronomic traits for selection towards improvement of Kenyan dual- purpose cowpea genotypes. The dendrogram also grouped the genotypes into three clusters, namely I (101), II (53) and III (70). There was congruence between the PC and hierarchical cluster in grouping the accessions, based on the Euclidean distance; with the highest values to be used for genetic improvement. The genotypic and phenotypic differences among the accessions could be leveraged as a basis for genetic improvement, through selection and crossing of parents with desired phenotypic traits in future breeding programmes.

Delimitation of cassava germplasm clusters in Kenya based on phenotypic traits

2025-01-10T14:48:11+00:00

Cassava (Manihot esculenta Crantz) is a staple food and more lately, cash crop in Kenya, supporting millions of stakeholders along its value chain. However, the phenotypic variability of the crop in the country is not fully understood. The objective of this study was to delimit clusters within the cassava germplasm in Kenya. The study involved 131 cassava stem cuttings of genotypes collected from seven major cassava growing counties in Kenya. Genotypes cuttings were planted in two experimental sites; namely Rongo University farm and Mawego Technical Training Institute farm. Data were collected on both quantitative and qualitative phenotypic traits, at three monthly intervals, during 3 to 12 months after planting. The data were subjected to Multivariate analysis (P<0.05). The cassava germplasm was categorised into four cluster groups based on phenotypic traits; namely Cluster 1 (72.5%), 2 (16.0%), 3 (3.1%), and 4 (8.1%) genotypes, respectively. Out of the 25 phenotypic characters assessed, a total of 11 principal components (PCs) trait sets accounted for 71.58% cumulative genetic variation (P<0.05). Furthermore, delimitation of these clusters was done based on the 11 assessed phenotypic traits. In Cluster 1, five PCs accounted for 61.7% of total variation among the genotypes. In Cluster 2, four principal components accounted for 69.2% of the variation; while in Cluster 3, two PCs explained 100% of the variation. In Cluster 4, four PCs accounted for 79.1% of the total variation among the genotypes. Delimitation of these clusters will inform targeted breeding strategies and conservation efforts.

Genome-wide association study reveals single nucleotide polymorphisms and candidate genes for resistance of cowpea to aphids

2025-01-10T14:55:55+00:00

Cowpea (Vigna unguiculata L. Walp.) is a major crop grown mainly in the arid and semi-arid regions for food and nutritional security. Its production, however, is generally hampered by its susceptibility to sap-sacking aphids (Aphis craccivora Koch). Resistance breeding for cowpea improvement against aphids, has been limited by inadequate understanding of genes responsible for resistance to this cosmopolitan pest. The objective of this study was to identify single nucleotide polymorphisms (SNPs) and candidate genes, associated with resistance of cowpea to aphids. The study evaluated 209 genotypes of the multi-parent advanced generation intercross (MAGIC) population, together with 5 MAGIC parents, cross three different locations for two seasons in Uganda. Significant genetic variation (P<0.001) for aphid resistance was detected in this germplasm. Results revealed three stable and significant SNPs, including 2_30668, 2_43528 and 2_43747; being associated with resistance to aphids. Eleven candidate genes were detected within the significant loci; including 7 genes on chromosome I (Vu01), 3 on chromosome VII (Vu07) and 1 on chromosome IX (Vu09). These putative genes have functions related to host plant resistance and plant defence responses, possibly against cowpea aphids. The significant SNP markers and genes reported may be deployed in marker-assisted breeding strategy, for faster development of aphid resistant cowpea varieties in Uganda.

Management and rationalised fertilisation of improved commercial production of potato mini-tubers

2025-01-10T15:06:10+00:00

Potato (Solanum tuberosum L.) is an important income earner and food security crop for many communities in sub-Saharan Africa (SSA). In Zimbabwe, mini-tubers are the commonly preferred as planting material, owing to their production under disease-free conditions. The objective of this study was to explore the effects of plant density, frequency of hilling and fertiliser regime, on commercial production of potato mini-tubers. A temperature-controlled greenhouse study was conducted at the Kutsaga Research Station in Zimbabwe; using Diamond potato variety. Treatments included plant density (375, 200 and 100 plants m-2), hilling (4 hilling intervals) and fertiliser regime (2 fertiliser regimes: 1 = supplemented with sulphate of potash; and 2 = supplement ammonium nitrate). The treatments were laid out in a completely randomised design, in a split-spilt plot arrangement; and set up repeated four times. Disease-free 28-day old potato plantlets were obtained from a tissue culture facility at Kutsaga Research Station, and planted in pots filled with Kutsaga soilless Growmixultra growth media. Plant density had a significant (P<0.05) effect on the mini-tuber size, with the highest plant density (375 plants m-2) having the most mini-tubers with sizes < 20 mm. Frequency of hilling only affected mini-tuber size, but not number of mini-tubers produced. Of the two fertiliser application regimes used, fertiliser regime 1 (High C, AN and SOP) had a significant effect on the survival of the potato plantlets and on the size of the mini-tubers. In a nutshell, in order to maximum mini-tuber production, a plantlet population density of 100 plants m-2, with weekly intervals of hilling under fertiliser regime 1, should be maintained to obtain the most viable commercial treatment combination.

Impact of site protection mechanisms on natural regeneration potential along a degradation gradient in Miombo Woodland region of the Democratic Republic of the Congo

2025-01-10T15:16:07+00:00

For several decades, the Miombo woodland located in Lubumbashi plain in the Democratic Republic of the Congo (DRC), has experienced significant changes in its floristic composition due to increasing human activity on the landscape, which has greatly impacted its potential for natural regeneration. Various human interventions have been implemented to protect this ecosystem, including the adoption of set-aside mechanisms with varying levels of protection. The objective of this study was to assess the effects of site protection mechanisms on the regeneration potential of vegetation, along a disturbance gradient, in the Miombo woodland of the Democratic Republic of the Congo. A study was conducted at Upper Katanga region in the Miombo woodland in the Lubumbashi Plain, involving a total of 60, 10 m x 10 m plots with 20 plots per site established across three sites, namely Kibundu, Kiswishi and Mikembo. Each plot was subjected to different levels of protection that is conservation with fence, without fence and forest communities-based management. A total of 1,230 individual trees were inventoried, representing 65 species, 45 genera and 20 families. Vertical spatial structure analysis revealed that the understory harbours greater species diversity than the upper canopy. The most represented families in the strata were Fabaceae, Apocynaceae, Phyllanthaceae and Ochnaceae. Additionally, Coefficient of Variation (CV) across the sites indicated uneven spatial distribution of three crowns within strata. Kibundu, with a CV of 102.9% in the upper canopy against 73.6% in Kiswishi and 18.4% in Mikembo, was found to influence the absolute density of individuals in the understory (CV =32.4, 61.5, 72.3% for Kibundu, Kiswishi and Mikembo, respectively). Interestingly, there was a high correlation between site disturbance rate of the potential of landscape regeneration (r =0.85, 0.055 and 0.77 at Kibundu, Kiswishi and Mikembo, respectively). Despite human pressures, regeneration indices were greater than unity, indicating a state of equilibrium in the vegetation of the Miombo woodland.