Phenotypic screening of cowpea (Vigna unguiculata (L.) Walp) genotypes for resistance to cowpea viral diseases

Viruses are a major constraint to cowpea production in sub-Saharan Africa. Host plant resistance is the most effective and reliable method of managing viral diseases. In order to identify the source of resistance or tolerance, 38 cowpea genotypes were screened for virus infection under field conditions during the 2016 wet and dry seasons. The experiment was laid out in a randomized complete block design with four replications in both seasons. Disease severity was assessed fortnightly based on disease symptom using 1-5 visual scale (1=symptomless, and 5= very severe symptom). The cowpea genotypes exhibited varying reactions to viral infections with mean disease incidence ranging from 17.7% in the fourth week to 29.2% in the eighth week for the wet season and from 34.4% to 53.1% for the fourth and eighth week, respectively in the dry season. Symptoms observed were leaf mosaic (86.7%), leaf mottling (86.7%), chlorotic spots (34.2%), vein clearing (28.9%), leaf curl (26.3%), necrotic lesions (15.8%) and stunting (10.5%). Symptom severity in the rainy season ranged from symptomless (severity score of 1) in IT10K-819-4 and IT07K-297-13 to moderate symptom (severity score of 2.9) in Apagbaala. However, in the dry season, the symptom severity score ranged from 1.11 (mild symptom) in Marfo Tuya to a score of 2.4 (moderate symptom) in IT07K-298-9, thus demonstrating a significant genotype x season interaction effect. Incidence and severity were significantly higher in the dry season than in the rainy season. There was a strong positive correlation between the disease incidence and disease severity as well as AUDPC and no correlation between the cowpea incidence and the seed yield and plant height in the wet season. There was a negative correlation between the incidence and plant height in the dry season. Six genotypes (IT07-210-1-1, IT07K-297-13, IT08K-193- 14, IT09-456, IT10K-817-3 and IT10K-819-4) exhibited mild symptoms and gave high yields in both seasons, thus demonstrating a stable G x E interaction effect. These disease resistant genotypes could be evaluated further before release to farmers.Keywords: Area Under Disease Progress Curve, Host resistance, Vigna unguiculata, Viral disease

Mineral composition and assessment of human ingestion risk of twelve accessions of Moringa oleifera Lam

Increasing consumption of moringa leaf powder in Ghana is boosted by popular claims that the plant contains a rich array of minerals, vitamins and other protective substances. However, the safe doses of this product among gender classes and vulnerable groups are unknown. This knowledge gap demands an analysis of the mineral composition of the product and estimation of the risk (hazard) potential associated with the ingestion of dried leaf samples of the moringa plant. Mineral composition (Na, Mg, P, K, Ca, Mn, Cr, Fe, Cu and Zn) of dried leaf samples of twelve accessions of Moringa oleifera Lam. was determined using the Atomic Absorption Spectrometry aided by a fast sequential Atomic Absorption Spectrometer. Results of the study indicate that the samples showed variation with respect to macro and micro minerals content and that dried leaf powder of moringa can serve as an excellent source of minerals. Additionally, an estimation of hazard exposure calculated as hazard index presented overall indices of 0.0866 and 0.0443 for males and females respectively. Even though the values (0.076-0.097; 0.038-0.051) obtained from the samples are within safe limits, it is essential that consumption of moringa leaf powder is done on sound advice from a nutritionist since crucial factors such as gender, age, health status and exposure time contribute to individual dose needs and influence mineral toxicity

Callus induction and plant regeneration via leaf segments of three accessions of African rice (Oryza glaberrimaStued.)

A study conducted with the aim of developing a protocol for callus induction and plantlet regeneration in vitro from leaf segments of three accessions of African rice (O. glaberrimaSteud.) indigenous to Ghana. Leaf segments of the accessions namely, Guame, N/4 and SARI 1 were assessed for callus induction and plantlet regeneration ability on different concentrations of plant growth regulators, incorporated into Murashige and Skoog, (1962) (MS) basal medium. Frequency of callus induction which was achieved on MS medium supplemented with (0-10) mg/l 2,4-D differed significantly (p≤0.05) among the accessions, as well as among the levels of 2,4-dichlorophenoxyacetic acid (2,4-D) tested. Highest callus induction frequency was exhibited at a concentration of 6 mg/l 2,4-D for all three accessions.Sub-culturing of callus on regeneration medium, which consisted of MS supplemented with (1:0-5) mg/l NAA:BAP resulted in no plantlet regeneration in all tested accessions. Instead, prolific root formation was observed

Spread of African cassava mosaic virus from cassava (Manihot esculenta Crantz) to physic nut (Jatropha curcas L.) in Ghana

Investigations were made on the susceptibility of physic nut (Jatropha curcas L.) to African cassava mosaic virus (ACMV) and its possible role as an alternative host of the virus in Ghana. Ten J. curcas accessions in a field trial were interplanted with ACMV-infected cassava (Manihot esculenta Crantz) and left to natural spread of the virus from the cassava to the J. curcas plants for a period of 12 months. Populations of the whitefly vector, Bemisia tabaci (Gennadius) and the incidence of African cassava mosaic disease (ACMD) were monitored during the period. The J. curcas plants had low whitefly numbers, both in the wet (September – October, 2008) season and in the dry (January – February, 2009) season. By the end of the experimental period, 37.7% of the 120 J. curcas plants tested in all the accessions were found to be infected by ACMV, as assessed by symptom expression, double antibody-sandwich (DAS) ELISA or sap inoculation to Nicotiana benthamiana indicator plants. There were wide variations within and between the J. curcas accessions in their response to ACMV infection. This work is the first report of the natural infection of J. curcas by ACMV

Field assessment of soil water storage and actual evapotranspiration of rainfed maize (Zea mays L.) genotypes in a coastal savannah environment

A field experiment was carried out in a coastal savannah agro-ecological zone of Ghana to assess the dynamics of stored soil water and actual evapotranspiration (AET) of three maize genotypes (Obatanpa, Mamaba, and Golden Crys- tal) grown under rainfed conditions. Access tubes were installed to a depth of 120 cm for soil water content monitoring using a neutron probe meter. The soil water balance model of plant root zone was used to estimate AET at different crop growth stages. On average, the rate of AET for Obatanpa, Mamaba, and Golden Crystal maize genotypes were estimated as 4.32, 4.46, and 3.72 mm·day−1, respectively, for the major cropping season as against corresponding values of 3.88, 4.00 and 3.72 mm day−1 for the minor cropping season. Mamaba had higher values of AET from 42 DAE (days after emergence) to 84 DAE during the minor cropping season while it had low AET values during the major cropping season. The positive balance in stored soil water in the root zone of Obatanpa was the highest from 42 DAE to 84 DAE followed by Mamaba and Golden Crystal during the major cropping season. Mamaba, on the other hand, had the high- est AET from 70 DAE to 84 DAE. Obatanpa used 55.6% of stored soil water for AET, which was the highest among the maize genotypes during the major cropping season. Golden Crystal and Mamaba followed with 53.3% and 51.5%. For the minor cropping season, 48.5% of stored soil water was used by Mamaba for AET, followed by Obatanpa, (46.4%) and Golden Crystal (43.2%). A strong positive significant (p ≤ 0.05) linear correlation existed between AET and precipitation with the coefficient of determination (R2) being 69.2 for Obatanpa, 88.5 for Mamaba and 82.8 for Golden Crystal for the major cropping season. Higher R2 values (98.0, for Obatanpa, 94.1 for Mamaba and 98.9 for Golden Crystal) were, however, obtained for the minor cropping season. Additionally, a strong linear relationship was found between AET and precipitation, suggesting the need to formulate strategies for enhancing effective use of pre- cipitation in sustained rainfed maize production.Justice Okona Frimpong, Marcus Quaynor Addy, Emmanuel Ofori Ayeh, Harry Mensah Amoatey, Jacob Teye Kutufam, Bertrand Quaye, Joshua Osei Sintim, Daniel Kwasi Asar

Selection and in-vitro propagation of five cassava (Manihot esculenta, Crantz) cultivars

Thirteen cassava cultivars were collected from farmers in the Greater Accra Region using a structured questionanire. Five cultivars namely, Ankrah, Bosom nsia, Biafra, Santom and Afisiafi were selected based on popularity, duration to maturity and tolerance to African Cassava Mosaic Virus (ACMV) disease. The cultivars were propagated in vitro using meristem, multiple shoots culture, and somatic embryogenesis. Meristematic explants were cultured on Murashige and Skoog (1962) basal salts and vitamins (MS) amended with NAA 0.1 mg/l, GA3 0.1 mg/l BA (0.0-0.15 mg/l BA). There was profuse callus formation in all the cultivars. The optimal concentration for shoot proliferation was 0.10 mg/l BA or 0.15 mg/l BA. With reduced NAA and GA3 concentrations (0.02 and 0.04 mg/l respectively) in the culture medium BA 0.05 mg/l was optimum with 100% and 46% shoot regeneration respectively in Bosom nsia and Santom compared to 37% and 0% in the ptevious treatment. All the selected cultivars formed multiple shoots from single bud cutting of in vitro plantlets. However, the number of apical shoots formed was dependent on BA concentration in the medium. Embryogenic calli formation on MS amended 2,4-D 0.0-16 mg/l depended on the type of explants. For greenhouse grown plants development of embryogenic calli from young leaf lobe and apical meristem explants was significantly higher than stipule explants. However, none of the calli were able to induce primary embryos when transferred to a maturation medium (MS plus 0.1 mg/l BA). Similarly embryogenic calli formation from tissue-cultured young leaf lobe explants on the same media were high in all the 2,4-D treatments. Subsequent production of primary embryo was low on the maturation medium and was found to depend on the cultivar and 2,4-D concentration. Somatic embryo formation was higher on 2,4-D 16 mg/l medium than on 4 mg/l or 8 mg/l 2,4-D medium. Santom produced the highest percentage of embryo (25%) among the cultivars used. Embryogenic calli which did not form somatic embryos formed roots which depended on the 2,4-D concentration of the induction medium. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 3, July (1999) pp. 31-4

Productivity and soil water use by rainfed maize genotypes in a coastal savannah environment

Polish title as appears on publisher's website: poprzedni artykuł wróć do listy artykułów następny artykułTotal aboveground biomass, grain yield and actual evapotranspiration data were used to estimate water use efficiency by the maize genotypes in terms of total dry matter and grain yield production. Grain yield and its associated water use efficiency were significantly different (P≤0.05) among the maize genotypes during the major cropping season, with Mamaba producing the highest grain yield of 7 250 kg ha-1 and water use efficiency of 13.2 kg ha-1 mm-1. For the minor season, however, no significant difference was observed in grain yield which ranged between 5 800 and 7 200 kg ha-1, with Obatanpa producing the highest grain yield. Similarly, no significant difference was observed in water use efficiency during the minor cropping season which ranged between 14.6 kg ha-1 mm-1 and 19.1 kg ha-1 mm-1, with Obatanpa having the highest water use efficiency. Maize genotypes Mamaba and Obatanpa were identified suitable for the rainfed conditions at the study area because of their comparatively high grain yield and better use of soil moisture for grain yield production.J.O. Frimpong, H.M. Amoatey, E.O. Ayeh, and D.K. Asar

Cultivation and use of African yam bean (Sphenostylis stenocarpa) in the Volta Region of Ghana

The African yam bean (Sphenostylis stenocarpa Hochst ex A. Rich) is a legumi nous crop found in the Volta Region of Ghana. Three expeditions were under taken in the region between September 1998 and March 1999 to investigate the extent of cultivation and use of the bean as the basis for research into its develop ment and promotion as a major crop. Its cultivation is currently localized around Nkwanta and Ho West Districts. It is grown as a minor crop in mixed associa tion with yam and cassava. It is used extensively in various dietary prepara tions and has potential for supplement ing the protein requirements of many families throughout the year. Its current low status as a minor crop means that this potential is largely unexploited. Re search efforts are required to improve its agronomic characteristics and promote its cultivation and use as a major crop. The Journal of Food Technology in Africa Volume 6 No.3, 2001, pp. 74-77 KEY WORDS: African yam bean, food security, Ghana, legume, pulse, Sphenostylis stenocarpa, under-exploited cro