Department of Crop Science

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Yield of plantain alley cropped with Leucaena leucocephala and Flemingia macrophylla in Kumasi, Ghana
(Agroforestry Systems, 2000-07) Banful, B.; Dzietror, A.; Ofori, I.; Hemeng, O.B.
The decline in yield of plantain has partly been attributed to inadequate soil moisture and pests, particularly nematodes. The objectives of the study therefore were to determine the effect of mulch from Leucaena leucocephala and Flemingia macrophylla (Willd.) Merr. grown as hedgerows on (i) soil moisture and temperature (ii) growth and yield of plantain and (iii) pathogenic nematode populations. The study was conducted from 1991 to 1994 in Kumasi, Ghana. Treatments comprised of leguminous plants, L. leucocephala and F. macrophylla, and a control (no leguminous plants), arranged in a randomised complete block design with four replications. The leguminous plants were planted in 1991 while the plantain was planted in 1992. Results indicated that the highest biomass yield was produced by F. macrophylla. Mulching with prunings of F. macrophylla resulted in significantly (P < 0.05) higher retention of soil moisture and lower soil temperatures than mulching with prunings of L. leucocephala. Growth of plantain determined by plant height, leaf production, pseudostem girth and yield were significantly greater in F. macrophylla mulched plots than L. leucocephala treatment and control plots where no mulch was applied. Plant parasitic nematodes isolated were Meloidogyne spp., Pratylenchus spp., Paratylenchus spp., Helicotylenchus spp., and Rotylenchus spp. Three years after planting of hedgerows, significantly (P < 0.05) higher populations of Meloidogyne spp. (367 per 100 g soil), Paratylenchus spp. (92 per 100 g soil), Helicotylenchus spp. (8 per 100 g soil), and Rotylenchus spp. (308 per 100 g soil) were associated with L. leucocephala hedgerow than with Flemingia macrophylla hedgerow (42.0, 83.0 per 100 g soil) and the control (74.50, 41.0 per 100 g soil). F. macrophylla has qualities that suppress nematode populations. The results clearly indicated the superiority of Flemingia macrophylla over Leucaena leucocephala as much for plantain production.
Effects of Etiolated Slip Management on the Establishment, Fresh Tuber Yield and Yield-Related Attributes of White Guinea Yam, Dioscorea Rotundata Poir
(Discovery and Innovation, 2000-12) Gyansa-Easmon, C.E.
The "slip" of white guinea yam, Dioscorea rotundata Poir refer to the leafless sprout with the associated cormous structure that develops from the stored tuber when the dormancy period is over. Under dark storage conditions, these slips are etiolated, whitish or pale yellowish, being devoid of chlorophyll. At the end of 3 weeks of presprouting in topsoil, they attained a dry matter content of 58.9%, representing a net increase in "morphogenetic efficiency" (ME) of 340.3%, compared to the unpresprouted. A field experiment elicited no significant fresh tuber yield differences between the "directly planted" and "prerooted" slips at 5 months after transplanting or planting. The "presprouted" ones produced significantly higher fresh tuber yield of 19.3 t/ha. The directly-planted, produced significantly superior tuber size of 362.6g relative to the presprouted or prerooted, although its number of tubers per h. of 24,785 was significantly lower than the 103,910 of the presprouted. The directly-planted and presprouted produced tubers largely in the conventional seed yam range (200-1000g). This was an indication that the etiolated slips - the presprouted form, could be a new source of planting material for commercial seed yam production. The plants exhibited a "bushy" canopy architecture rather than viny and thus staking may not be necessary.
Variation in seed size, protein and tannin content of bambara groundnut (Vigna subterranea)
(Tropical Science, 2001-01) Ofori, K.; Kumaga, F.K.; Bimi, K.L.
Seed size and protein and tannin contents were determined on 25 accessions of bambara groundnut currently available in Ghana, using dried seeds 8-10 weeks after harvesting. The 100-seed weight varied from 34 to 63 g. The protein and tannin contents were 14.1 to 23.1% and 0.25 to 2.27% (dmb) respectively. Tannin concentration increased with increase in testa colour and eye pattern colour. Selecting accessions with high protein and low tannin, with large or medium seed size should improve the quality of bambara groundnut.
Effect of poultry manure and/or inorganic fertilizer on the yield of shallot [Allium cepa var. aggregatum (G. Don)]
(Advances in Horticultural Science, 2002-01) Blay, E.T.; Danquah, E.Y.; Ofosu-Anim, J.; Ntumy, J.K.
The study was carried out to determine the optimum levels of poultry manure, inorganic fertilizer and their combined effect on yield of shallots grown on sandy Anloga soils in Ghana. Treatments comprised a 4x3 factorial combination of poultry manure at 0, 10, 20 and 40 tons/ha and three levels of NPK 15-15-15 fertilizer at 0, 300 and 600 kg ha-1 in a randomised complete block design with four replications. A combination of 40 tons/ha of poultry manure with 300 kg/ha and 6000 kg/ha of NPK 15-15-15 fertilizer increased plant height, number of leaves per plant and number of plantlets per plant. Although application of inorganic fertilizer alone or in combination with poultry manure significantly increased bulb yield, there was a decrease in dry matter content. Sole application of 40 tons/ha gave the highest bulb yield. Our results demonstrate that farmers in the Anloga district of Ghana can rely on organic matter alone applied at 40 tons/ha for shallot production.
Hordein variation and reaction to powdery mildew in composite cross XLII of barley
(Genetica, 2002-01) Danquah, E.Y.; Barrett, J.A.
A bulk hybrid population, CCXLII was investigated for hordein variation and reaction to powdery mildew. The results indicated that the population in F4 was genetically variable and contained an appreciable proportion of heterozygotes. Evidence was found for differential viability within families. This was possibly the result of a high segregation load. The pattern of genetic variation suggests that although the population could be a useful source of breeding material for the selection of new lines, it may be risky as a method of conservation of germplasm.
Grain yield in Composite Cross Five of barley: Effects of natural selection
(Journal of Agricultural Science, 2002-03) Danquah, E.Y.; Barrett, J.A.
A range of three generations from each of three populations of Cambridge Composite Cross Five of barley spanning a period of 18 years of cultivation in Cambridge was evaluated for grain yield over 2 years in the field in 1991 and 1992. The design of the experiment was a randomized complete block with two replications. In 1991, the yield of the best composite cross generation was 78 % that of Atem, a commercial variety bred for N.W. European conditions. In the drought-affected year, 1992, three of the composite cross generations performed better than Atem. It is suggested that composite cross populations may be useful in deriving lines for low-input agriculture. © 2002 Cambridge University Press.
Evidence of natural selection for disease resistance in Composite Cross Five (CCV) of barley
(Genetica, 2002-06) Danquah, E.Y.; Barrett, J.A.
Cambridge Composite Cross Five (CCV) of barley was studied utilising hordeins, restriction fragment length polymorphisms (RFLPs) and reaction to powdery mildew with a view to understanding the genetic changes occurring in the population. Changes in the frequency of individual hordein patterns as well as pattern combinations showed directional trends in successive generations in three parallel populations maintained as discrete populations since 1977 in Cambridge. Certain hordein pattern combinations were more common in the resistance classes and there was a strong association between hordein patterns and mildew reaction. RFLP analysis revealed that 80% of a random sample taken from generation F24 of Population I had the same restriction pattern as that of the cultivar Algerian, which was one of the original 30 parental lines of CCV. This cultivar is the source of the Mlal allele in barley improvement programmes in Europe. We argue, based on supporting evidence from hordein analysis and tests of reaction to selected mildew isolates of known virulence isolates together with UK virulence surveys, that selection for Mlal in Cambridge has been the predominant evolutionary force in CCV in Cambridge.
Toxicity of palm oil to eggs and larvae of Callosobruchus maculatus (F.) on stored cowpea
(Insect Science and its Application, 2002-09) Osekre, E.A.; Gbewonyo, W.S.K.; Ayertey, J.N.
A commercially produced palm oil brand, Palmin oil, was evaluated for its effect on eggs and larvae of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) on cowpea (Vigna unguiculata (L.) Walp. Application of 1 μl of the oil on eggs deposited on 10 cowpea seeds, or directly on larvae growing inside seeds resulted in their death. Embryo mortality occurred only when the oil was placed at the anterior end of the egg. The nutritive content of cowpea seeds treated with Palmin oil remained unchanged. Furthermore, the oil did not go rancid following six months of storage. © 2002 ICIPE.
Isolation and characterization of microsatellites in Echinochloa (L.) Beauv. spp.
(Molecular Ecology Notes, 2002-09) Danquah, E.Y.; Hanley, S.J.; Brookes, R.C.; Aldam, C.; Karp, A.
Five primer pairs were developed that amplify microsatellite loci in three agronomically important Echinochloa (L.) Beauv. species: E. colona (L.) Link, E. crus-galli (L.) Beauv. and E. crus-pavonis (Kunth) Schultes. The microsatellites were tested on 24 individuals representing three species collected in rice fields from different geographical regions and revealed 3-7 alleles per microsatellite. Gene diversity [1 - σpij 2] for four polymorphic loci within E. crus-galli ranged from 0.12 to 0.61. Alleles at a fifth locus were useful in discriminating the species. The microsatellites should provide useful markers for intraspecific diversity studies and aid classification of species within this complex genus.
Genetic diversity in Echinochloa spp. collected from different geographic origins and within rice fields in Côte d'lvoire
(Weed Research, 2002-10) Danquah, E.Y.; Johnson, D.E.; Riches, C.; Arnold, G.M.; Karp, A.
Diversity studies of Echinochloa spp. are complicated by problems in taxonomy and species identification, caused by the existence of morphologically intergrading types. Six amplified fragment length polymorphism (AFLP) primer combinations and five microsatellites were used to assess variation in 24 samples morphologically identified as E. crus-galli, E. colona and E. crus-pavonis, from Bangladesh, India, Colombia, Costa Rica, Côte d'Ivoire and Philippines. Out of 909 AFLP bands generated, 775 were polymorphic. Genotype diversity for the microsatellites ranged from 0.28 to 0.72. Similarity matrices were calculated using Jaccard coefficient, and input into cluster and principal coordinates analyses. AFLP and microsatellite results were highly correlated. Echinochloa crus-pavonis and E. crus-galli were intermixed, consistent with the view that E. crus-galli occurs as numerous intergrading races in the four countries (Bangladesh, India, Côte d'Ivoire and Philippines). The E. colona samples clustered as a distinct group. In 15 samples of E. crus-pavonis collected from rice fields in a valley in Côte d'Ivoire (over a 2-km distance), four different genotypes were found in a 4 m x 4 m area. These results suggest that AFLPs and SSRs may be useful not only for discriminating genotypes and studying population structure but also for helping to resolve taxonomic relationships in Echinochloa spp.
The horticultural industry in Tropical Africa
(Acta Horticulturae, 2003) Norman, J.C.
In recent times there has been a tremendous interest and increase in horticultural crop production with a consequent high demand for horticultural products in many tropical African countries. This is the result of many favorable factors including: 1. the urgent need to limit importation of horticultural products to conserve scarce foreign exchange; 2. the recognition of the nutritional importance of fruits and vegetables in the diet. This is coupled with increased standard of living and education; 3. increase in processing factories; and 4. the high export potential of many horticultural products. The latter has been the prime mover of the industry. Tropical African countries are now exporting, not only, fruits and vegetables, but also flowers. The horticultural industry is, however, beset by several constraints. The major economic and technical constraints are outlined and methods of overcoming them are indicated.
Variation in size, protein, cyanide and tannin contents of lima bean (Phaseolus lunatus)
(Tropical Science, 2003-09) Offei, S.K.; Asante, I.K.; Danquah, E.Y.
Thirty one accessions had 100-seed weight of 23.8 to 71.8 g and protein contents from 20.4 to 30.3%. There was little variation in cyanide content. Tannin contents varied tenfold among the accessions and increased with colour.
Assessment of grain yield losses in pearl millet due to the millet stemborer, Coniesta ignefusalis (Hampson)
(Insect Science and its Application, 2003-09) Drame-Yaye, A.; Youm, O.; Ayertey, J.N.
Studies were conducted at the ICRISAT Sahelian Centre, Niger, to assess damage and yield loss by the millet stemborer, Coniesta ignefusalis (Lepidoptera: Pyralidae) on Pennisetum glaucum (L.) R. Brown. Although 78% of stems were infested, late attack by the millet stemborer on millet plants resulted in bored stems yielding more than unbored ones. Artificial infestations with 5 and 10 larvae per plant at 2 weeks after plant emergence (WAE) resulted in 50 to 70% plants with deadhearts and 24 to 100% avoidable yield loss. At 4 weeks after plant emergence, infestations with 5 larvae and 10 larvae per plant resulted in 7% increase in yield and 16% yield loss, respectively. Therefore, both the age of plant and density of borer population at the time of infestation can influence resulting stemborer damage and yield loss on pearl millet. © 2003 ICIPE.
Genetic structure of seventy cocoyam (Xanthosoma sagittifolium, Linn, Schott) accessions in Ghana based on RAPD
(Hereditas, 2004-04) Offei, S.K.; Asante, I.K.; Danquah, E.Y.
Seventy cocoyam accessions collected from the eastern and Volta regions of Ghana were studied using RAPD technique. Ten primers were used to study the genetic diversity and structure of the experimental material and a total of 120 different bands were detected. Levels of polymorphic fragments detected by the ten primers ranged from 69.2% to 100%. In the accessions from the eastern region, the mean observed and effective number of alleles per individual per population and mean Nei's gene diversity were 1.99±0.01, 1.53±0.12 and 0.312±0.05, respectively. Mean observed and effective number of alleles per individual per population and Nei's gene diversity were 1.76± 0.17, 1.44±0.16 and 0.264±0.08, respectively for the accessions from the Volta region. Considering the entire collections, the mean observed and effective number of alleles per individual per population and Nei's gene diversity for primers were 1.99±0.02, 1.54±0.12 and 0.319±0.05, respectively. In terms of Nei's F-statistics in the subdivided populations for all primers, the overall gene diversity (Ht) ranged from 0.230 to 0.396 with a mean of 0.313+0.06, within sample gene diversity (Hs) ranged from 0.214 to 0.372 with a mean of 0.286+0.06, gene differentiation (Gst) ranged between 0.005 and 0.178 with a mean of 0.086. Geneflow estimate ranged between 2.309 and 99.500 with a mean of 5.314. The accessions grouped into three main clusters. Accession BD96/183 was the most diverse and may be incorporated into cocoyam breeding programs. The 70 accessions did not cluster into their distinct geographical regions suggesting that there may have been movement of germplasm across the two regions.
Molecular variation of Potato yellow vein virus isolates
(Archives of Virology, 2004-04) Offei, S.K.; Arciniegas, N.; Müller, G.; Guzmán, M.; Salazar, L.F.; Coutts, R.H.A.
To evaluate the variation of Potato yellow vein virus from potato fields, 12 isolates were collected from Colombia and one was collected from Peru. Double-stranded RNA was extracted from the plants and used as a template for RT-PCR amplification of the coat protein (CP) gene and, in separate reactions the C-terminal region of the heat shock protein 70 homologue (Hsp70h) gene and the N-terminal region of the p60 open reading frame. The CP amplicons were subjected to single-strand conformation polymorphism (SSCP) analysis and, together with the other amplicon, nucleotide sequence analysis. These analyses suggested that there is low genetic diversity in the PYVV isolates examined and that the Peruvian isolate of PYVV may have originated in Colombia. © Springer-Verlag 2003.
Causes of low productivity of cocoa in Ghana: Farmers' perspectives and insights from research and the socio-political establishment
(NJAS - Wageningen Journal of Life Sciences, 2004-12) Dormon, E.N.A.; Van Huis, A.; Leeuwis, C.; Obeng-Ofori, D.; Sakyi-Dawson, O.
Ghana is a major producer of cocoa in the world and relies heavily on the crop for foreign exchange revenue. However, production declined since the mid-1960s, reaching its lowest level in 1983, Although production has increased consistently since the mid-1980s, it still is less than the level attained in the mid-1960s. The decline is partly a result of decreasing areas under cultivation. Another problem in cocoa production in Ghana is low yields per ha, which is attributed to the incidence of pests and diseases, a low producer price, and non-adoption of research recommendations. Based on the idea that current research and extension messages might insufficiently address farmers' actual problems and context, a diagnostic study was carried out to better understand farmers' views on the problems of cocoa production. The study was conducted in three villages in the Suhum-Kraboa-Coalter District, Eastern Region, Ghana. An action research approach was followed to gather and analyse qualitative data with the objective of stimulating collective action in subsequent research activities with the farmers. Low productivity was identified as the main problem and the causes were classified into biological and socio-economic factors. The biological factors include the incidence of pests and diseases, most of which have received extensive research attention in Ghana, and of epiphytes, which have been neglected. The socio-economic causes were indirect and include the low producer price and the lack of amenities like electricity, which leads to migration, with as a result labour shortages and high labour costs. From the study it can be concluded that the biological and socio-economic causes of low productivity are inter-related in such a manner that tackling them separately will not overcome the problem unless the socio-technical nature of the causes are recognized and tackled in a holistic way. In this context, current interventions by research and extension seem to ignore important aspects of the problematic situation. Although the study shows the relevance of using a diagnostic approach, it is argued that outcomes may be affected by various contextual factors, including stakeholder selection and the relationship between the researcher and the participants. Hence, the outcomes of a diagnostic study should be approached with care.
Linking science and farmers' innovative capacity: Diagnostic studies from Ghana and Benin
(NJAS - Wageningen Journal of Life Sciences, 2004-12) Röling, N.G.; Hounkonnou, D.; Offel, S.K.; Tossou, R.; Van Huis, A.
The article is an introduction to a series of articles about diagnostic studies carried out by eight PhD students in Ghana and Benin. These studies form a prelude to their experimental action research with groups of farmers to develop technologies that work in local conditions and are acceptable to farmers. A last article reports on a comparison of these eight studies by the ninth PhD student in the Convergence of Sciences (CoS) project. In this introductory article, it is argued that the need to ground agricultural research in the needs and circumstances of farmers is as strong as the need to ground research in the international scientific discourse. It explores the reasons why the West African context requires careful diagnostic studies to be able to design agricultural research that is of any use. It introduces pre-analytical choice as an overriding concept to explain why choices that reduce the degrees of freedom have to be made explicitly on the basis of criteria. Such criteria are suggested for the quality of pre-analytical choices, and the paper ends by examining the way the CoS project made some of its choices.
The influence of postharvest conditioning and storage protocols on the incidence of rots in White Yams (Dioscorea rotundata Poir.) in Ghana
(Acta Horticulturae, 2005) Bancroft, R.D.; Crentsil, D.; Panni, J.Y.; Aboagye-Nuamah, F.; Krampa, L.
The post-harvest conditioning of root and tuber crops (such as potatoes and cassava) by exposure to elevated temperature and humidity ('curing') has long been used to extend their storage life. The use of this strategy on yams is not, however, well documented and appears not to be practised with any consistent conviction in West Africa. During the period 2000 to 2003, a series of on-farm trials was conducted on White Yams (Dioscorea rotundata Poir.) in Ghana to assess whether curing and other related protocols could be exploited. The factors investigated included the impact of yam variety, tuber maturity (immature 'milk' yams and physiologically mature 'ware' yams), different curing environments (plastic bags, clamps or modified storage rooms) and subsequent storage in different structures (pits or barns). Interactions were observed between the conditioning treatments and varieties, and the different storage structures had a significant impact on yam weight loss, sprouting and the incidence and prevalence of rots. Overall 'milk' yams were more prone to deterioration than 'ware' yams and, irrespective of the possible benefits of curing, were much better conserved in traditional pits than in barns. Irrespective of treatment, rots were more often associated with the upper sections of the tubers, suggesting a link with pre-harvest insect damage and harvest cuts at the site of the vine. It was determined that the levels of relative humidity in pits, clamps and modified storage rooms could engender curing, whereas the humidity in plastic bags was excessive and simply brought about rapid rotting. Achieving the correct temperature for curing was problematic. Ambient temperatures (high 20°C) proved sub-optimal whereas temperatures above 37°C were too high. These field trials suggest, however, that the conditions necessary to cure yams can be established in rural communities with limited resources.
Susceptibility of Amblyomma variegatum ticks to acaricides in Ghana
(Experimental and Applied Acarology, 2005-03) Natala, A.J.; Agyei, A.D.; Awumbila, B.
The susceptibility of unfed and fed stages of larvae, nymphs and adult females of Amblyomma variegatum ticks were tested using Shaw's filter paper dip method against four acaricides; chlorfenvinphos and dioxathion, chlorfenvinphos, gamma benzene hexachloride and amitraz at four different concentrations including the recommended dose rates. Based on their lethal concentrations (LC50 & LC90) chlorfenvinphos and dioxathion combined and chlorfenvinphos alone placed first and second, respectively, in all stages except at the unfed nymphal stage where gamma benzene hexachloride topped with a LC50 of 0.001629, while chlorfenvinphos and dioxathion combined and chlorfenvinphos alone had LC50 of 0.001794 and 0.002258, respectively. Amitraz appeared to have a quick knock-down effect on larvae and nymphs but at the recommended dose rate, showed no mortality of the ticks at that stage. However, at a concentration of 0.040%, amitraz showed a 100% inhibition of oviposition and hatching of laid eggs. Gamma benzene hexachloride produced only 66% inhibition of oviposition while chlorfenvinphos and dioxathion combined and chlorfenvinphos alone produced 100% inhibition of oviposition at their recommended dose rates. Fed nymphs were more susceptible than the unfed nymphs. Eggs laid by engorged female ovipositing ticks, applied with gamma benzene hexachloride, hatched. © Springer 2005.
Efficacy of mixing vegetable oils with pirimiphos-methyl against the maize weevil, Sitophilus zeamais Motschulsky in stored maize
(Journal of Stored Products Research, 2005-05) Obeng-Ofori, D.; Amiteye, S.
Sitophilus zeamais is a major insect pest of stored maize and grain products in the tropics. The toxicity of coconut, groundnut and soybean oils applied at 1, 2, 5 and 10ml/kg and pirimiphos-methyl at 2.5, 5 and 10μl active ingredient in 2ml of water/kg of grain (116, 18 and 14 of the recommended dose), alone or in combination, to adults and immature stages of S. zeamais, the persistence of the treatments in maize grains and their effects on seed viability were evaluated in the laboratory. All the treatments caused significant mortality compared to untreated controls. Low dosages of the oils and pirimiphos-methyl when combined were highly toxic to adult S. zeamais. The mixtures completely inhibited the development of immature stages of the weevil. Only pirimiphos-methyl and the mixtures retained some activity 60 days after application. Pirimiphos-methyl can be used at reduced rates if combined with vegetable oils to control infestations of S. zeamais in stored maize. © 2004 Elsevier Ltd. All rights reserved.

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