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Tropical Science

Wiley Online Library : Tropical Science

Published: 2007-12-01T00:00:00-05:00


Green-maize potential of hybrid and open-pollinated cultivars at varying levels of applied nitrogen: relationship with grain yield


Two sets (white- and yellow-kernelled) of six cultivars of field-maize, each comprising three hybrids and three open-pollinated (OP) varieties, were evaluated for green-maize productivity under three levels of nitrogen fertilisation (0, 60 and 120  kg  ha−1) at two locations in southwestern Nigeria. The relationship between green-maize and grain yield was also investigated. Numbers of marketable ears and marketable-ear yield were significantly correlated. Green-maize traits and grain yields showed different responses to increased nitrogen fertiliser application: grain yield was significantly greater at 120  kg  ha−1 than at 60  kg  ha−1 whereas marketable-ear yield was not significantly changed by the higher rate. The hybrids showed higher green-maize and grain yield responses than the OPs to fertiliser application. At 60  kg  ha−1 nitrogen application, marketable-ear yield averaged 0.620  kg  m−2 and 0.567  kg  m−2 for white hybrids and OPs, respectively, and 0.576  kg  m−2 and 0.439  kg  m−2 for yellow hybrids and OPs. Marketable-ear yield was significantly correlated with grain yield for both the white and yellow cultivars. Regressions of grain yield on marketable-ear yield were significant and such regression equations can thus be used to estimate marketable-ear yield potential from grain yield data. Copyright © 2008 John Wiley & Sons, Ltd

Agronomic and nutritional characteristics of fourteen Ghanaian groundnut varieties


The growth and yield parameters of 14 groundnut varieties were evaluated at three locations in Ghana, and key physical and nutritional characteristics of the grains were measured and compared. Kernel yields ranged from 940 kg ha−1 to 1463 kg ha−1. Grain length and 100-grain mass were not consistently and strongly correlated, and the inconsistency may be partly due to differences in oil content, which has implications for processing of the different varieties. The protein content of the varieties ranged from 25.6% to 29.6% and many of the varieties would be suitable for dietary protein supplementation. No variety scored consistently highly for all characteristics, but varieties CSTV404MB and CS-49 grew very well, and had high protein contents and moderately high oil contents, so they can be recommended for oil extraction and protein supplementation of local diets low in protein. Copyright © 2008 John Wiley & Sons, Ltd

Effect of roasting time and storage time on sensory attributes and consumer acceptability of peanut butters in southern Africa


This study explored how sensory attributes and consumer acceptability of peanut butters varied with differing roasting times (40 to 55 min) and storage times (up to 48 weeks) for shelf-life testing. Quantitative descriptive analysis generated sensory terms that were appropriate to the local situation. Increased roasting time was associated with the sensory attributes brown colour, roasted taste and burnt taste. Consumer acceptance varied among consumers with two preferred roasting times of either 40 min (67% of consumers) or 50 min (23% of consumers). This was related to distinct peanut flavour profiles. During the storage study of five selected butters consumer acceptability did not alter with storage period. Sensory testing, however, was more sensitive to product changes: sensory attributes that varied with storage were sticky texture, stale odour and sweetness. Copyright © 2008 John Wiley & Sons, Ltd

Seed yield, oil content and fatty acid composition of three botanical sources of ω-3 fatty acid planted in the Yungas ecosystem of tropical Argentina


Studies have shown that the fatty acid composition of oils consumed can affect the risk of cardiovascular heart disease, and many consumers are therefore looking for sources of ω-3 fatty acids. Three herbs of the family Lamiaceae, chia (Salvia hispanica L.), golden chia (Salvia columbariae Benth.) and winter savory (Satureja montana L.), all of which produce seeds rich in ω-3 fatty acid, were planted in northwestern Argentina to determine their production potential in terms of seed yield, oil content and fatty acid composition. Chia seed had the highest oil content (29.9%), followed by golden chia (21.0%) and winter savory (8.0%). All three crops exhibited similar fatty acid profiles, with α-linolenic ω-3 fatty acid being the largest component. Golden chia had the highest α-linolenic fatty acid content: 17% and 11% more than chia and winter savory, respectively. Golden chia's shattering, however, is a major disadvantage for commercial production, making this the least attractive crop of the three. Copyright © 2008 John Wiley & Sons, Ltd

Nutritive value of different varieties and morphological fractions of oats harvested at the soft dough stage


Chemical composition and in vitro organic matter digestibility (IVOMD) were measured in whole forage and morphological fractions of 20 varieties of oats (Avena sativa) harvested at the soft dough stage. Among the varieties, crude protein (CP) varied from 48 to 76 g kg−1 dry matter (DM), neutral detergent fibre (NDF) from 586 to 683 g kg−1 DM, acid detergent fibre (ADF) from 370 to 482 g kg−1 DM and lignin from 54 to 83 g kg−1 DM. The IVOMD of the whole forage ranged from 43 to 62%. Among the morphological fractions, leaf blades had the highest CP content and IVOMD, whereas the fibre constituents (NDF, ADF and lignin) were highest in the stems. The results revealed considerable variation in chemical composition and IVOMD among the oat varieties and morphological fractions. This implies that there are opportunities for improving forage production and quality from oats through appropriate exploitation of varietal differences. However, manipulation of management practices (such as choice of harvesting stage, use of mixed cropping with compatible legumes and fertiliser application) may still be needed for further improvement. Copyright © 2008 John Wiley & Sons, Ltd

On-farm evaluation of methods for storing fresh sweet potato roots in East Africa


Methods for sweet potato storage, previously developed at a research station, were tested on-farm by subsistence farmers in Lake Zone, Tanzania. On-farm testing confirmed that the methods were suitable but indicated that practical and simple improvements were necessary, without which losses in the proportion of market-quality roots from the store could be as high as 79%. These practical improvements were mainly concerned with the position of stores on the farms. The addition of a new step, dehaulming, improved the recovery of market-quality roots by 48%. However, although the storage methods were developed in order to improve farmer income, most farmers said they would use the stored roots as a subsistence staple for household food security. Variations among the farmers in their attitudes to storing sweet potato suggest that, when transferring methods from the research station to the farm, it is necessary to target those most able to adopt the approach. Additionally, the farmers considered that local market traders may not be keen to sell stored roots. Therefore, other actors in the value chain, such as market traders and consumers, ought to be included in the process of transferring methods from the research station to the farm. Copyright © 2008 John Wiley & Sons, Ltd

Changes in the thiamine and riboflavin contents of rice during artisanal parboiling in Ghana


Rice samples mildly parboiled at various combinations of soaking temperatures and steaming times were analysed for their thiamine and riboflavin contents. The relative parboiling index was calculated and this provided a reliable measure of the overall effects of different conditions on the degree of parboiling. The thiamine content of parboiled rice samples increased gradually as parboiling intensity was increased from initial soaking temperature at 30°C and steaming for 4 min to soaking at 70°C and steaming for 12 min. There was a sharper rise in thiamine when the soaking temperature was increased to 90°C, and the sample that was steamed for 12 min after soaking at 90°C had a thiamine content of 0.612 µg g−1. The level of riboflavin also initially increased with parboiling, but it peaked at 0.278 µg g−1 in the sample that was soaked at 70°C and steamed for 12 min, and then decreased as parboiling intensity was increased further. The commercially parboiled rice sample had a riboflavin content of 0.206 µg g−1. This pattern of change in riboflavin levels with parboiling was probably due to thermal breakdown of the vitamin at higher soaking temperature. Copyright © 2008 John Wiley & Sons, Ltd

Soil respiration curves as soil fertility indicators in perennial central Amazonian plantations treated with charcoal, and mineral or organic fertilisers


We assessed substrate-induced respiration and soil chemical properties in order to study the influence of charcoal, nitrogen and phosphorus fertilisation on two different perennial crops in a confounded factorial design on a highly weathered Amazonian upland soil. Each plantation tested three different factors in three different levels making up 27 (33) treatment combinations. Whereas the banana plantation received mineral fertilisation in addition to charcoal applications (3rd factor), the guarana (Paullinia cupana) plantation was fertilised organically using chicken manure and bone meal as the corresponding factors. Charcoal increased pH, total nitrogen, availability of sodium, zinc, manganese, copper and soil humidity, and decreased aluminium availability and acidity in the mineral-fertilised plantation only. This caused a significant increase in basal respiration and microbial efficiency in terms of carbon dioxide release per microbial carbon in the soil. The microbial biomass, efficiency and population growth after substrate addition was significantly increased with increasing levels of organic fertiliser amendments. We conclude that charcoal is a valuable component especially in inorganic-fertilised agricultural systems. Copyright © 2008 John Wiley & Sons, Ltd

The biology, ecology and economic importance of the pink scavenger caterpillar Pyroderces rileyi (Lepidoptera: Cosmopterigidae) on banana in Jamaica


The pink scavenger caterpillar Pyroderces rileyi Walsingham (Lepidoptera: Cosmopterigidae) is a recent pest of bananas in Jamaica. The larval faecal pellets result in scarring of the banana fruit. The pest occurs on several crops, including cotton, sorghum and maize, across the world. Its biology in Jamaica, food plant preferences and impact of the recommended control method are examined. Adult trapping methods are investigated. Development from egg to adult took an average of approximately 37 days. The number of larvae increases with the age of the bunch, probably due to decreased amounts of latex as the bunch matures. Adult male moths were caught using traps baited with (E)-11-tetradecenyl acetate as a pheromone lure. Pheromone lures based on a related species, P. simplex Walsingham, were tested but a second minor (< 10%) component, (E)-11-tetradecen-1-ol, present in P. simplex did not appreciably enhance the attractancy of the acetate component. Deflowering was effective as a control measure, significantly reducing adult numbers as well as the level of scarring. Copyright © 2008 John Wiley & Sons, Ltd

Diagnosis, occurrence and seed transmission studies of viruses infecting four Centrosema species in Nigeria


In a survey to detect viruses affecting Centrosema species in two agroecological zones in Nigeria (the derived and northern guinea savanna zones: DSZ and NGSZ), enzyme-linked immunosorbent assay of leaf samples of four species (C. brasilianum, C. pascuorum, C. pubescens and C. macrocarpum) revealed infections of two Potyviruses – Bean common mosaic virus and Cowpea aphid-borne mosaic virus – and three Comoviruses – Cowpea mosaic virus, Cowpea severe mosaic virus and Bean pod mottle virus. Other viruses detected included: a Carmovirus, Cowpea mottle virus; a Cucumovirus, Cucumber mosaic virus (CMV); a Sobemovirus, Southern bean mosaic virus; and a Tobamovirus known as Tobacco mosaic virus (TMV). While no viruses were detected in leaf samples of C. brasilianum and C. pubescens collected from NGSZ, leaf samples of the same species collected from DSZ were highly infected, with the former being infected with seven viruses and the latter with all nine viruses tested for. Seed transmission studies of these viruses in Centrosema species showed CMV to be the most frequently detected, followed by TMV, and four different viruses were found in seeds of C. brasilianum in DSZ. The paper discusses the implications of these results for cropping of Centrosema legumes. Copyright © 2008 John Wiley & Sons, Ltd

Effects of roasting time and storage time on sensory attributes and consumer acceptability of peanut butter in southern Africa


By Keith Tomlins, Tunga Rukuni, Angeline Mutungamiri, Sheila Mandeya & Anthony SwetmanThe above article (DOI:10.1002/ts.210) was published online on 9th July 2008 in Wiley Interscience An error was subsequently identified in the article.Page 8, Figure 3 Text – now includes the x-axis ConsumerPage 8, Figure 3 – amendment to the figure legend as followsFigure 3. Agglomerative hierarchical cluster analysis dendrogram for segmenting consumers (n = 103) into groups of similar perceptions of peanut butters prepared from the Valencia variety roasted for differing times. Dashed line denotes level of dissimilarity along which the four segments (clusters) were selected; x-axis is not annotated because the number of labels was too high to be legible.The print publication will incorporate the amendments identified by this erratum notice