Starches isolated from Malawian sweetpotato, cocoyam and cassava were comparatively studied and evaluated for physicochemical, functional and structural properties in order to unveil their characteristic properties and unravel their potential for industrial application. Further, sweetpotato and cocoyam starches were modified by physical and chemical means, and changes in their functional properties were determined. The results showed that cocoyam, sweetpotato and cassava starch exhibited properties that were unique to botanical source. The pH of the starches ranged within the 4.7 to 7.0 range required for use in low acid foods while moisture content was below the maximum limit required for prolonged storage of the starches. Ash and amylose content of the starches ranged from 0.03 to 0.28%, and 10.6 to 34.4%, respectively while protein and fat levels ranged from 0.35 to 0.84%, and 0.085 to 0.160%, respectively. All starches exhibited high levels of potassium, followed by calcium, phosphorus, magnesium and sodium. Iron, manganese and zinc were present in very low levels compared to the other elements. Cocoyam starch granules exhibited mostly round/spherical shapes similar to that of cassava starch, while sweetpotato starch granules were mostly polygonal in shape. Granule size ranged from 4.0 to 18.7 ï­m, 4.0 to 48.0 ï­m and 5.3 to 22.7 ï­m for cocoyam, sweetpotato and cassava starches, respectively. Cocoyam starch had a larger fraction of smaller sized (0-10 ï­m) granules than sweetpotato and cassava starch. Sweetpotato and cassava starches had mostly medium sized (10-25 ï­m) granules. All starches exhibited B-type crystallinity with distinctive major diffraction peaks at 5.4-5.6° 2ï± angles, however relatively strong peaks at 7.6-7.8° 2ï± angles suggesting the presence of single helical conformations. Water absorption capacity, swelling power and solubility of all starches increased with increasing temperature. Cassava starches exhibited higher water absorption capacity, swelling power, paste clarity, resistance to retrogradation and viscosity than cocoyam and sweetpotato starches. Cocoyam starches exhibited higher gelatinization temperatures than sweetpotato and cassava starches. Cocoyam and cassava starches gave similar gelatinization enthalpies which were higher than those of sweetpotato starches. Cocoyam starches displayed higher retrogradation tendencies than sweetpotato and cassava starches. Cocoyam starches displayed higher blue values and wavelength of maximum absorption but lower reducing capacity values than sweetpotato and cassava starches. There was similarity in the packing and orientation of chains in the amorphous regions of sweetpotato and cocoyam starches as evidenced by similar values of the extent of acid hydrolysis of the starches for 12 days. Average molecular weight of amylopectin molecules of the starches studied by HPSEC ranged from 1.42 x 106 to 1.67 x 106 Da. Cocoyam starch contained amylose molecules of lower molecular weight than sweetpotato and cassava starches. Analysis of isoamylase debranched starches showed that sweetpotato starch had the largest fraction of long-chain amylopectins (47%) and the lowest fraction of short-chain amylopectins (45%), while cocoyam starch exhibited the largest fraction of short chain amylopectins (62%) and smallest proportion of large chain amylopectins (32%). Acetylation enhanced water absorption capacity, swelling power and solubility of the starches, but reduced gelatinization temperatures, gelatinization enthalpy and retrogradation tendencies of the starches. Acid hydrolysis reduced the water absorption capacity and swelling power but improved the solubility and paste clarity of starch, and increased gelatinization temperatures and enthalpy. Annealing reduced water absorption capacity, swelling power, solubility and pastes clarity but increased gelatinization temperatures and enthalpy. Due to their differences in physicochemical, functional and structural properties, starches from Malawian cocoyam, sweetpotato and cassava can play different roles in the Malawian industry.

The genotype effect of South African barley cultivars on malting quality under different nitrogen applications was determined by planting two- and six-row doubled haploid populations consisting of 7 and 67 lines respectively under irrigation at Vaalharts in 2006 and 2007 and at Rietriver in 2007. Three different nitrogen (N) treatments were applied to correlate the amount of leaf N to N in the kernel to implement a practical N fertilizer management system to obtain good malting quality. For treatment one, all of the fertilizer (110 kg/ha) was applied at planting. For treatments two and three, half of the fertilizer (55 kg/ha) was applied at planting while the other half (55 kg/ha) was applied at the sixleaf stage or when 50% of flag leaves were visible respectively. The best N application for the two-row population was treatment three compared to the six-row population which responded differently to all the N applications over years and localities. This study indicated that a practical N fertilizer strategy should include half the N application at planting (55kg/ha) for crop and tiller development and a split application of the other 55 kg/ha at six-leaf and flag leaf stage to enhance kernel plumpness, germination, absorption and yield and maintain optimum kernel N for good malting quality. Timing of N application had a significant effect on all the malting quality traits. However, RP-HPLC results of hordein fractions showed that there was no change in the composition of hordeins in response to timing of N application and to the environment. The two- and sixrow entries within a doubled haploid population differed in malting quality across environments. Genotypes contributed more to variation in a population than the environment for both kernel plumpness and yield. However, for kernel N, the environment contributed more to variation than the genotypes. There were significant correlations between malting quality traits and hordein fractions. In particular, the negative correlation between kernel plumpness and total hordein content at treatment two. Total hordein content forms the majority of total kernel N content and plumpness is known to be associated with low kernel N content. The different barley genotypes were identified by their distinct hordein patterns with RP-HPLC. The C and B hordeins were able to distinguish between two- and six-row genotypes. Averaged across all N treatments, kernel N and protein content was positively correlated with the D:B hordein ratio and negatively correlated with the B:C hordein ratio which indicates that malting quality was reduced.

Malnutrition, including vitamin A deficiency, and food insecurity are national priorities in South Africa. Sweet potato has several agronomic advantages giving it potential to address both priorities. The crop is popular amongst resource-poor farmers as it is easy-to-grow and hardy. Orange-fleshed genotypes (β-carotene-rich) are used internationally in crop-based approaches to address vitamin A deficiency. Due to a shortage of varieties with desirable traits for resourcepoor farmers, several new varieties have been developed. The overall objective of this study was to evaluate the agronomic performance, sensory quality and nutrient content of new South African varieties. The ANOVA of new varieties in MET, indicated significant differences in dry matter content, marketable yield, number of marketable roots and total yield. AMMI and GGE biplot analysis showed that cream-fleshed varieties Ndou and Lethlabula produced yields comparable to the commercial variety Blesbok. Ndou (unstable high yield), Mokone and Monate (stable, average yields) and Amasi (moderately unstable, average yield) had dry matter content similar to the control variety Mafutha (known for sweet and dry taste). Recommending these new varieties will have a considerable yield advantage over Mafutha, with a possible impact on food security. From MET with nine orange-fleshed varieties the ANOVA and GGE SREG analysis indicated that Impilo produced stable, high yield and 2001-5-2 unstable, high yield. Both had average dry matter content. The two varieties offer a significant yield advantage above USA imports, previously recommended to address vitamin A deficiency. Orange-fleshed varieties produced significantly lower yield than cream-fleshed ones. Raw roots of nine orange-fleshed varieties, harvested from MET at four agro-geographical production sites, had an overall mean trans-β-carotene content of 5091 to 16456 μg/100 g. Resisto, Khano, 2001-5-2, W-119, Beauregard and 1999-1-7 exceeded 5500 μg/100 g β-carotene (breeding target). Dry matter content ranged from 23.1% (Impilo) to 28.7% (W-119). The content of six minerals was determined. Consumption of a boiled portion of 100 g raw root of all nine varieties can potentially contribute to â¥100% of the recommended intake for vitamin A, 21% of magnesium, 12% of zinc and 9% of iron for 4 to 8 year old children. CIE L* and a* color measurement of nine varieties with varying orange flesh color had the best correlations with total β-carotene content, and is a faster selection method. A mathematical function with natural logarithm (ln) transformation derived to predict total β-carotene content from color L*, predicted 91% of the values with >75% accuracy. The color and taste acceptability of boiled sweet potato of new varieties were evaluated in two experiments by grade 1 â 7 learners and adults in a BIBD using a 5-point hedonic scale. A trained panel found clear differences in the sensory attributes of the varieties. Cream to yelloworange varieties, Mafutha, Lethlabula and Phala had the highest consumer panel (n=190) scores, associated most with wateriness, discolor, graininess, gumminess, sweet potato-like flavor and instronforce. Orange-fleshed varieties Impilo, Excel, Resisto, 2001-5-2, Serolane and W-119, and cream-fleshed varieties Monate and Ndou were acceptable to the second consumer panel (n=216), mostly related to dry matter content, maltose content, sweet flavor, wateriness, discoloration and dark edges. High maltose and starch content were found in Ndou, Serolane, Resisto and Monate; while Blesbok, Impilo and 2001-5-2 had high fructose and glucose content. Orange-fleshed varieties were as acceptable as cream-fleshed varieties. The present study provides novel results on G x E analysis, comprehensive and systematic determination of nutrient content, consumer and sensory assessment of a considerable number of new cream to orange-flesh sweet potato varieties promoted in South Africa. Varieties Ndou, Mokone, Monate and Amasi were recommended to address food security; and Impilo and 2001- 5-2 to address vitamin A deficiency.

The important socio-economic position enjoyed by sorghum has made it a target for genetic modification to enhance productivity and/or nutritional quality. However, there are growing environmental concerns that through geneflow, transgenes might escape from genetically modified (GM) sorghum to its sexually compatible wild and/or weedy relatives, with possible negative effects. Characterising the levels and dynamics of geneflow in the wild-weedy-domesticate complex of sorghum in traditional agroecosystems of Africa, including Kenya, is of interest to biosafety regulators. This study used approaches based on population genetics theory to (i) characterise the genetic structure of the wild-weedy-domesticate complex of S. bicolor at a country scale in Kenya and (ii) to estimate the extent and direction of geneflow between cultivated and wild-weedy populations at a local scale in the country. The structure and dynamics of diversity was first estimated and compared at country scale by genotyping 329 cultivated and 110 wild sorghum individuals using 24 microsatellite markers. Subsequently, the magnitude and direction of geneflow between the two congeners was estimated at a local scale by analysing 483 individuals comprising of 15 wild-weedy and 12 cultivated sorghum populations using 10 microsatellite markers. Overall, cultivated sorghum harboured lower diversity than its wild counterpart. Levels of genetic diversity in cultivated and wild sorghum differed significantly among regions, with most of the diversity being partitioned more within than among the cropâs growing regions. There were generally low levels of differentiation within and between cultivated and wild sorghum at country scale, but the extent of crop-to-wild genetic proximity varied among sorghum growing regions. These findings may reflect important historical geneflow between cultivated sorghum and its progenitor, with the level of crop-to-wild genetic exchange varying among regions. At local scale, the extent of geneflow was approximately nine times higher from cultivated sorghum to its wild-weedy relatives than vice versa. Additionally, the extent of crop-to-wild geneflow varied significantly among farms. Overall, this study suggests that deployment of GM sorghum in Kenyaâs agroecosystems will most likely lead to movement of transgenes into sympatric populations of its wild-weedy relatives.

Fusarium head blight is one of the most important wheat diseases under irrigation and currently there are no cultivars resistant to this disease in South Africa. The main aim of this study was to determine the virulence of Fusarium graminearum isolates, to test growth and sporulation on different media and to do screening for resistance in the greenhouse and field. Twenty Fusarium graminearum single spore isolates from the Prieska region were evaluated in the greenhouse to determine the virulence of the isolates on a susceptible wheat cultivar. The isolates that were most virulent were A191, A145, A144, A149, A204 and A223. These isolates did not differ significantly from each other in the greenhouse test. Five of these isolates were used in the laboratory to determine which solid medium can be used to produce an abundance of spores. Potato dextrose agar, carrot agar, malt extract agar with 5 g chopped maize straw and mung bean agar were used. The growth of the isolates was measured over a seven day period. From the data it was evident that malt extract agar and mung bean agar were the best media to use for growth within the seven day period. Each of the media was tested weekly for up to four weeks to determine which of the isolates produced the most spores when given optimum conditions. Mung bean agar was the best medium to use for spore production. Considering the other media, potato dextrose agar may be used for identification, multiplying and storage of Fusarium isolates. Carrot agar is suitable to induce spore production, but is generally used as a medium for fertility studies. Malt extract agar containing sterile, chopped maize straw may be used for growth rather than for inducing spore formation. A lower amount of malt extract should be used to reduce the amount of maltose in the medium to increase spore production. Isolate A191 was used in the other two greenhouse tests. The first test was to determine the best inoculation technique for inducing FHB. Five different cultivars were included, namely SST825, SST822, Krokodil, Frontana and a derivative of Sumai #3 (SUM3/3/CS/LE.RA//CS/4/YANGMAI 158). Three techniques were used, namely cotton wool, straw and spray inoculation. From the data obtained it was clear that the cotton wool method was the best inoculation method to use to test Type II resistance. In a second greenhouse test, 13 lines from the 9th SRSN, CIMMYT, Mexico, were tested with isolate A191 using the cotton wool technique. The results showed that there were no differences between the moderately susceptible SST825 and numbers 74 and 54 (Type II resistance). The second group can be classified as a moderately resistant group that included numbers 54, 39, 21, 34, 50, 47, 19, 5, 57, 61 and 3. Number 14 was classified as resistant and the Sumai #3 derivative as a very resistant cultivar. Two field trials were executed in 2007 and 2008, respectively. The 9th SRSN from CIMMYT, Mexico, were included in the trials for both years. The field experiment consisted of the honeycomb moving grid design. The isolates used for both years included numbers were A144, A145, A146, A149, A151, A156, A159, A161, A166, A167, A169, A176, A183, A187, A191, A194, A204 A221, A223 and A269. These isolates were prepared on mung bean medium, harvested and sprayed four times, at two-day intervals, onto wheat plants during flowering. The environmental conditions for the 2007 trial were excellent for infection. Data from 2007 showed that entry 66 was susceptible. Thirty-three lines showed resistance, 29 lines showed moderate resistance and five showed moderate susceptibility. SST806 and Marico were used as a susceptible and moderate resistant control, respectively. The environmental conditions for 2008 were not conducive and very low levels of infection were obtained. Grain spawn was used in conjunction with spray inoculation to improve the inoculum pressure during 2008. Although extra inoculum was added, a low infection percentage was noted. Thus, field trials should be executed for at least three seasons before meaningful recommendations can be made.

The objectives of the study were to evaluate the adaptability of 17 experimental maize genotypes under the maize growing environments of Ethiopia, to select the best hybrids for commercial production, to utilize various statistical procedures for analyzing G x E interactions and yield stability of Ethiopian maize hybrids across nine environments and to indicate breeding strategies for releasing genotypes with adaptation to target environment. Seventeen experimental maize hybrids, including a locally released standard check, were evaluated for grain yield in a mid altitude areas of Ethiopia, for a period of three years (2004 to 2006) across three locations. The genotypes were planted in a completely randomized block design. G x E interactions and variance components were calculated using factorial analyses. Stability parameters were calculated using various parametric and non-parametric methods. While, a cluster analysis was done to classify the different genotypes and environments. The computer programmes, Agrobase Generation II (Agronomix, 2008), SAS (SAS Institute Inc., 2003) and NCSS 2004 (Hintze, 2001) were utilized to perform the different analyses. The mean squares for G x E interaction were found to be highly significant for yield including the variation among the genotypes (G). The Location (L) and Location x Year (L x Y) interactions have the largest components of variance for grain yield, which is an indication of the variation among testing sites and year to year fluctuation of the weather. The experimental maize hybrid PR1 (mean yield =7.14 t ha-1) was found to be the highest yielder followed by PR13 (6.77 t ha-1) .This result shows the potential of the experimental genotypes to be released for commercial production. Highly significant correlations (P<0.01) was obtained among Eberhart and Russellâs deviation from regression (S2 di), Wrickeâs ecovalence (Wi), Shuklaâs ( ) 2 i s stability variance and AMMI Stability Value(ASV). Mean yield and Lin and Binnsâs cultivar superiority performance (Pi) showed high correlations but they showed no correlations with the rest of the stability parameters. The non-parametric measure of Nassar and Hühnâs absolute rank difference S(1) and variance of ranks S(2) was significantly correlated (P 0.05) with ASV, however they did not correlate with the rest of the parametric measures. Based on the different stability parameters, hybrids PR1, PR13 and BH540 were found to be more stable and responsive to favourable environments while SE21 and SE22 hybrids showed their stability in the low yielding environments. Since, ASV showed higher correlations with both parametric and non-parametric measures, and the mean yield, it is recommended to use ASV as a stability parameter in identifying stable genotypes from multi-environment trials. The analysis of variance for the AMMI model indicated highly significant differences between genotypes and environments as main effects and the interaction effect of G x E was also highly significant. The first two interaction principal component axes (IPCA) of the AMMI model together accounted between 34% and 56% of the total G x E interaction sum of squares for grain yield. The AMMI biplot categorized the genotypes PR1, SE4, PR2, PR3, BH540 and PR13 as well adapted to favourable environments with above average yield. Hierarchical clustering using unweighted pair group method with arithmetic average (UPGMA) grouped the genotypes into five and the environments into three clusters. The results from the study of optimum allocation of resources indicated that allocation of two or three replications, three to five locations for three to four testing years will give adequate information for yield estimates, help to minimize trial costs and provide more precise data for variety release decisions in Ethiopian condition. The research also proved that locations-years tradeoffs are more effective than locations/years-replications tradeoffs in getting statistically efficient data from a maize yield trial.

Cocoyam (C. esculenta (L.) Schott and X. sagittifolium (L.) Schott) belongs to the family Araceae. Cocoyam has the potential to contribute significantly to world agriculture in terms of food, nutrition and crop diversification. Despite this the crop remains neglected in terms of research focus. Limited or no information exists on the prevalence, preference and utilisation as well as the pattern and level of diversity that exists in cocoyam germplasm found in Malawi. This study determined the level and pattern of genetic diversity of cocoyam from Malawi using ethno-botany, morphological characters and AFLP markers. Mineral composition of selected genotypes was also determined. The ethno-botanical survey showed that farmers in Malawi maintain a large amount of cocoyam germplasm. These farmers have rich ethno-botanical and ecological knowledge of the cocoyam cultivars they conserve. Farmerâs preferences regarding cocoyam cultivars included uses of plant parts, adaptation and eating quality. Morphological characters showed high levels of variation among accessions. Two main species of cocoyam, Colocasia and Xanthosoma were identified based on leaf base shapes (petiole attachment). AFLP markers showed low levels of genetic diversity between accessions as opposed to the high morphological diversity. A combined (morphological characters and AFLP data) analysis using UPGMA clustering, PCA and AMOVA further alluded to the presence of the two cocoyam species within the germplasm. High levels of variation were detected between the two species and low levels of variation were observed within each of the two species (Colocasia and Xanthosoma). The PCA exhibited a better representation of the genetic diversity pattern than the hierarchical clustering. Accessions showed high levels of mineral composition. Potassium was identified as the major mineral component. Accessions also exhibited high levels of essential minerals (Ca, Fe and Zn). Incorporating cocoyam into the diet of the resource poor farmers could help in the fight of the most prevalent micro-nutrient deficiencies. A study on morphological and genetic diversity as well full nutritional assessment of the tubers and leaves of cocoyam from the whole country is recommended. In order to broaden the narrow genetic base observed importation of foreign material is recommended.

The association between hexaploid wheat (Triticum aestivum L.) quality parameters and gluten protein were determined for selected South African wheat cultivars. Reversed-phase high-performance liquid chromatography (RP-HPLC) and size-exclusion HPLC (SE-HPLC) were used to separate protein fractions. The influence of the environment was much higher for RPHPLC fractions than for SE-HPLC fractions, and genotype contributed much more to the expression of SE-HPLC. Correlations between yield, kernel characteristics and milling properties were low for both chromatography procedures. Bread making properties showed significant correlations with HPLC fractions. RP-HPLC gluten fraction showed the best correlation with alveograph strength and loaf volume. Polymeric proteins showed the highest correlation with mixograph development time, alveograph extensibility, tenacity and configuration of the curve. This confirms the effect of gluten on dough strength and extensibility. Narrow sense heritability indicated that large polymeric proteins could be considered for indirect selection of alveograph and mixograph parameters

High oleic acid sunflower hybrids have been available on the market for a few years, but research on the stability of these genotypes for oil quality traits in South African production areas is limited. General aims of this study were to compare oil quality traits of high oleic sunflower against traditional sunflower genotypes in different environments, over seasons and under heat stress conditions and to identify possible genetic markers related to the oleic acid trait that would be useful in breeding programmes. Combined ANOVAs of oil, linoleic, oleic, palmitic and stearic acid content of 16 genotypes tested in a total of nine trials over eight locations and three seasons showed highly significant differences between genotype, environment and GXE. Significant GXE suggested differential response of genotypes across testing locations and years and the need for stability analyses. Stability analyses were performed for all oil traits using AMMI. Stability analyses indicated that high oleic genotypes 6 and 8 could be considered stable across environments and seasons for oil and oleic acid content and genotype 9 for palmitic and stearic acid content. Sunflower oil quality is affected by genotype and environmental conditions with temperature as a major influence. The effect of heat stress on seed yield and oil quality traits was investigated by applying a maximum temperature of 36ºC to plants during the critical seed-filling stage. This information was needed to define a breeding strategy to further improve seed oil quality in environments where heat stress may occur. All traits measured were significantly influenced by heat stress. The low heritability estimates observed for seed-related yield traits indicated that genetic improvement for these traits would be difficult. Oil and linoleic acid contents were significantly reduced by heat, while oleic acid content was significantly increased in traditional hybrids. The oleic acid content of the high oleic acid hybrid was unaffected, but this hybrid showed the largest decrease in oil content. High heritability estimates observed for oleic and linoleic acid content indicated that it is possible to genetically improve these traits under different temperature conditions. Since oleic acid content is influenced by the environment, this trait showed instability across environments. Genotypic selection for this trait using linked markers is independent from the environment. A segregating population comprising 78 F2 individuals was obtained from a cross between a high oleic acid and traditional sunflower line. AFLP and SSR markers were used to identify and map QTL, associated with the high oleic acid trait, putatively to LG 14 of the sunflower consensus map. A major QTL controlling the level of oleic acid was identified that explained 35% of the phenotypic variance for this trait. Markers linked to this trait were identified that could be useful in MAB. Physicochemical properties and oxidative stability of seed oil of high (82.6% oleic) and mid oleic acid (53.8% oleic) sunflower hybrids were compared with those of traditional sunflower (65.7% linoleic and 22.9% oleic). Oxidative stability was evaluated by measuring PV, p-AV and OSI values. High oleic acid oil had the best oxidative stability. Since oxidative stability was related to the unsaturation level of oil, the high oleic oil with significantly reduced linoleic acid content had the highest resistance to oxidation. Keeping quality of commercially available vegetable oils, including high oleic sunflower oil was evaluated using the Schaal oven test. Oil samples, placed in a heat cabinet at 63ºC were periodically examined for keeping quality by determining PV, p-AV and RI values. High oleic sunflower oil was twice as stable as traditional sunflower and canola oils.

Mango (Mangifera indica L.) belongs to the Anacardiaceae family. Consumption is increasing worldwide due its their nutritional value that is rich in vitamins A and C, potassium, β-carotene, fibre as well as proteins. Mangoes are economically important for Mozambique because of suitable climatic conditions and international market opportunities. This study compared morphological and AFLP characterisation of 30 mango varieties from the Umbeluzi research station, including some commercial varieties: âKeittâ, âKentâ, âHadenâ, âSensationâ and âRubyâ. Morphological characterisation using IPGRI descriptors were divided into quantitative (23 characteristics) and qualitative (58 characteristics) data. The total variation was lower using quantitative (89.4% similarity) than qualitative data (60% similarity). The combined quantitative and qualitative dendrogram had 63% similarity and clustered varieties in three subgroups based on high fruit weight, high Brix content and low fruit weight. AFLP characterisation used seven primer combinations, generating 207 data points and detecting 74.9% polymorphism with an average of 30 fragments per primer combination. The total variation was low (72.49% similarity) and the dendrogram showed two main groups subdivided in five subgroups based on low fruit weight, dwarfness and low Brix content, high fruit weight and roundish fruit shape. The combined morphological and AFLP dendrogram was more accurate in clustering varieties based on geographic origin within the country and from outside. The dendrograms presented in the study will help breeders to select parents for crosses. PCA results confirmed the pattern of clustering of varieties based on fruit weight and Brix/acidity ratio. It is recommended to extend the study to include, the entire collection at Umbeluzi and to include morphological data, considering pest and diseases resistance characterisation, as well as genetic and cytological analysis. A study of genotype x environment interactions done over years should be undertaken in future.