African Crop Science Journal

Variabilité et gain génétique des génotypes de haricot biofortifiés à l’Est de la République Démocratique du Congo

2024-03-28T06:33:31+00:00

La compréhension du mécanisme génétique responsable du contrôle des caractères agronomiques est très importante dans la mise en évidence des méthodes de sélection en amélioration végétale. Cette étude veut apprécier le niveau de variabilité et gain génétique au sein des génotypes des haricots biofortifiés à Butembo et Lukanga à l’Est de la République Démocratique du Congo. Une expérimentation a été réalisée sur 164 génotypes biofortifiés en Fe et Zn et cinq variétés locales (non-biofortifiés). Les données ont été prises sur le nombre de jours à la floraison, nombre de jours jusqu’à 75 et 90% de la maturité, nombre de gousses par pied et nombre de graines par gousse, le rendement en graines et le poids de 100 graines et soumises à l’analyse de la variance et au test de Tukey avant d’estimer les paramètres génétiques. La corrélation de Pearson et le clustering ont enfin été réalisés. Des différences significatives ont été observées entre le contraste qui oppose les génotypes biofortifiés aux variétés témoins localement cultivées au regard de tous les caractères étudiés à l’exception du nombre des gousses initiées par plant et le rendement. Les génotypes RW298, BF08-16-36A, BF08-1-77, RWV2359 et MV-14, avec un rendement supérieur à 2000 kg ha-1, ont été les plus prometteurs au regard du rendement. L’estimation des composantes de la variance a montré une héritabilité (sens large) modérée au regard du nombre de jours à la floraison et faible pour tous les autres paramètres. Aussi, le coefficient de variation génotypique a été modéré uniquement au regard du rendement et faible pour tous les autres caractères. Le gain génétique dans les générations courantes a été faible (<10%) pour tous les caractères étudiés impliquant une action non-additive des gènes dans le contrôle des caractères au sein des génotypes étudiés. Une corrélation positive significative a été observée entre le rendement et le nombre de gousses par plant et le nombre de graines par gousse. La construction du dendrogramme a permis de regrouper quatre clusters importants (Cluster 1 = 49 génotypes, Cluster 2 = 30 génotypes, Cluster 3 = 42 génotypes and Cluster 4 = 48 génotypes). Au regard des résultats observés, il est recommandé d’effectuer des sélections au sein du cluster 2 (couleur bleue du dendrogramme) regroupant les génotypes les plus prometteurs au regard du rendement ou d’exploiter l’hétérosis au sein des génotypes en étude.

Détermination de l’orientation géographique des pièges pour la détection des mouches des fruits dans les vergers de manguiers du nord de la Côte D’Ivoire

2024-03-28T06:54:00+00:00

Le manguier (Mangifera indica L.) est une culture fruitière majeure dans le secteur de l’exportation de la Côte d’Ivoire. Actuellement, la Côte d’Ivoire est le troisième fournisseur de mangues sur le marché européen, après le Brésil (100 000 t) et le Pérou (80 000 t). Cependant, la productivité des fruits de mangue en Côte d’Ivoire (3 à 7 t ha^-1) reste faible par rapport à celle obtenue dans des conditions optimales de culture (10 à 20 t ha^-1). La prolifération des mouches des fruits (Diptera : Tephritidae) est l’une des principales causes de la baisse de productivité des mangues. Pour les éliminer dans les vergers de manguiers, des techniques de piégeage incluant des paraphéromones sont nécessaires. L’objectif de cette étude était de déterminer l’orientation géographique optimale des pièges pour la capture des mouches des fruits dans les vergers de manguiers du nord de la Côte d’Ivoire. Des attractifs sexuels ont été placés dans des pièges le long des quatre directions cardinales du verger de manguiers. Les résultats montrent que Bactrocera dorsalis et Ceratitis cosyra sont les espèces les plus abondantes dans les pièges. En outre, selon les quatre directions cardinales, les pièges orientés vers le nord ont capturé davantage de B. dorsalis, tandis que les pièges orientés vers l’ouest ont capturé davantage de C. cosyra. Cependant, l’orientation géographique des pièges selon les quatre directions cardinales n’a pas eu d’influence sur la détection des mouches des fruits dans les vergers de manguiers.

Genetic diversity and heritability of tomato parental lines assembled for Ralstonia solanacearum resistance

2024-03-28T08:08:06+00:00

Bacterial wilt is a disease caused by Ralstonia solanacearum, which affects over 450 plant species and causes significant reduction in crop yields including of tomato (Solanum lycopersicum) worldwide. Developing and identifying tomato genotypes with Ralstonia solanacearum tolerance and high yield potential, presents an opportunity for improvement of crop productivity. The objective of this study was to explore the heritability of tomato resistance against bacterial wilt and the genetic variation within the population for breeding purposes. A breeding population was created by crossing two bacterial wilt-resistant (MT56 and BL333) and three commercially desirable susceptible (Assila, Rambo and Heinz) tomato varieties, using North Carolina Design II, in a screen house at the Makerere University Agricultural Research Institute, Kabanyolo (MUARIK). Results showed that the Area Under Disease Progress Curve was significant (P<0.001), indicating that cumulative disease progress was less in resistant genotypes of segregating generations. Disease severity increased with days after inoculation (DAI), with Heinz showing the highest level of susceptibility. The General Combining Ability for male parent (GCAm) was significant (P< 0.01), and Specific Combining Ability (SCAf×m) and GCAf were significant (P<0.01) for the F2 generation. Broad-sense heritability was higher than the narrow-sense heritability in both F1 and F2 generations, suggesting that non-additive gene action predominately controlled tomato resistance to bacterial wilt infestation. The genetic diversity ranged from 0.5 to 0.6759, with a mean value of 0.5787. Polymorphism Information Content (PIC) varied from 0.375 to 0.6357, with a mean of 0.4888, indicating a high degree of variation. SLM 12-2 was the most polymorphic marker, with a PIC of 0.6357. The Unweighted Pair-Group Method with Arithmetic Average (UPGMA) classified all tomato genotypes into six clusters, namely Clusters 1 and 2 (Susceptible parents), Cluster 3 (Resistant parents), Clusters 4 and 5 (New source of resistance), and Cluster 6 (F1P1×P5).

Causal agent for disease symptoms on passionflower in Adim, Cross River State, Nigeria

2024-03-28T08:17:43+00:00

The stinking passionflower (Passiflora foetida L.) is generally regarded as a weed, although its tender fruits are consumed by a few; while the plant is mostly regarded for its medicinal properties. Cucumber mosaic virus is known not just to cause significant losses among crops, but also present in many weeds species. The objective of this study was to identify the causal agent of the disease symptoms observed from P. foetida in Adim, Cross River State, Nigeria. Leaves of P. foetida with virus symptoms were collected from various locations in Adim. Antigen-coated plate enzyme-linked immunosorbent assay (ACP-ELISA) and reverse transcription polymerase chain reactions (RT-PCR) were used for virus detection and characterisation. The symptomatic leaves reacted positively with the CMV antisera in ACP-ELISA and sequences from RT-PCR products showed the highest identity (98.5%) with a CMV isolate from Xanthosoma sp. (MG021460) in Uganda. Phylogenetic reconstruction aggregated the isolates with other Nigerian CMV sequences in a separate uncharacterised subgroup, closest to MH798809 (Nigeria), MW655577 (Nigeria) and HQ874434 (Austria). The tree also revealed the isolates as members of subgroup IB. This study provides the first molecular evidence of CMV infection on P. foetida in Nigeria and adds to the list of possible natural host for the virus in the country.

Determination of combining ability and heritability for canning quality traits in common bean

2024-03-28T08:23:44+00:00

Breeding for common bean (Phaseolus vulgaris L.) genotypes with optimal canning quality holds the potential for increased dry bean consumption among middle-class income urban dwellers in sub-Saharan Africa (SSA). Understanding the genetic control of canning quality traits is central for the improvement of common bean genotypes for desired canning quality. The objective of this study was to determine the combining ability and heritability of canning quality traits (CQTs) in common bean; and to establish entry points for effective breeding for these traits. A population from two contrasting parents for canning quality traits was developed and progressed to F2. The F2:F4 seed was evaluated for CQTs at three months post-harvest. Substantial variation was observed among the canning quality traits tested, including the general appearance of the canned beans, seed coat colour retention namely, clumping, free starch, splitting, and hydration coefficient. Canning quality traits encompassed a spectrum of both additive and non-additive effects. Promising combiners for CQTs were identified among the parents, KK8 and MAC 13, suggesting their potential for utilisation in breeding programmes. Moderate to high Baker’s ratio (BR = 0.41-0.94) values were observed for some CQTs and narrow sense heritability (h2 = 0.47-0.66). Canning quality traits exhibited substantial broad sense heritability (H2) values, ranging from 0.6 to 0.92. These findings provide valuable entry points for breeding programmes focused on improving common bean for canning quality.

Parasitic nematode populations associated with developmental stages of mango in production regions of Ghana

2024-03-28T08:36:01+00:00

Nematode (Phylum nematoda) infestation is a major set back in mango (Mangifera indica) production world-wide. Control of nematodes requires understanding of their diversity, distribution and population densities. The objective of this study was to identify plant-parasitic nematodes associated with mangoes and their population densities at seedling and maturity stages in production regions of Ghana. The study was conducted in Greater Accra (Manya and Klagon) and the Eastern region (Somanya) during December 2016 to January 2018. Mango farmlands were surveyed for soil and root samples, from which nematodes were extracted, identified and quantified. Twenty-four nematode genera were identified in mango seedlings and matured trees from Somanya; and 14 genera dentified in seedlings and 22 in matured trees from Manya; while at Klagon, 15 nematode genera were identified in matured trees. Helicotylenchus spp. were the most populated in seedlings obtained from Somanya and Manya, with relative abundance of 23.29%. Tylenchus spp. had the highest population in mature trees, with relative abundance of 24.49% at Somanya and 38.86% at Manya; while Helicotylenchus spp. had the highest relative abundance of 43.96% at Klagon. Mature trees had higher nematode population densities, compared to seedlings. There were significant variation in nematode populations between seedlings and matured stages of mango.

Impact of Korra tef adoption on farm household productivity and incomes in Central Ethiopia

2024-03-28T08:43:53+00:00

Tef (Eragrostis tef) is a major staple and income sourcing crop in the horn of Africa; that has attracted tremendous investment particularly in research. It is expected that the improved seed varieties will contribute to raising farm productivity and consequently, farmers’ income. The objective of this study was to assess how the adoption of improved tef variety has influenced household productivity and incomes, with a focus on the Korra tef variety introduced by the Agricultural Growth Programme phase II, in Ethiopia. Cross-sectional data were collected from 479 randomly selected farm households, in two woredas in Central Ethiopia; one as an adopter and the other as a non-adopter. The Propensity Score Matching (PSM) approach was used to investigate the adoption of the Korra tef variety and its impacts on household production and income, over the yield obtained by the non-adopters. The PSM model’s robustness was tested using regression on variables and regression on propensity scores. The adoption of the Korra tef variety, according to the PSM approach, increased tef productivity by 598.78 kg (nearly 6 quintals) per hectare, over the yield obtained by the non-adopters. Additionally, switching to the Korra tef variety raised household income by US$ 806.73 per hectare. We conclude that the adoption of Korra tef variety increases the productivity and incomes of adopter farm households.