Popcorn is the most popular snack food in the world. Genetic diversity is of major concern in popcorn breeding. High genetic diversity allows manipulation of different genotypes to breed new varieties. There is very little published work on popcorn production in Sub-Saharan Africa primarily in South Africa. Popcorn production in South Africa could be hampered by the lack of superior and adapted varieties with large genetic base, good popping ability and high yield. Studies relating popping expansion volume and grain yield are of fundamental importance for popcorn improvement, but they are limited. Furthermore, there is limited number of studies regarding popcorn genetic diversity among locally developed popcorn varieties. The objectives of the study were; (i) to investigate genetic variability among the popcorn inbred lines, (ii) to study the magnitude of genetic diversity among the popcorn inbred lines, (iii) to establish the relationship between popping ability and seed yield, and with secondary traits, and (iv) to evaluate the effect of popping methods on popping ability of different popcorn inbred lines. Two populations designated as Population 1 and Population 2 with 83 and 81 inbred lines, respectively, were used in the study.On the study of the appraisal of popping methods, the highest popping expansion volume (cm³) and less number of unpopped kernels were obtained from hot air popping than in the microwave popping method. The study revealed that hot air popping method is more effective and efficient in discriminating popping ability of the inbred lines. The study further revealed that the two methods rank genotypes differently. The presence of genotype × popping method interaction resulted in three different groups. (i) Genotype adaptation across methods, (ii) specific adaptation to microwave popping, and (iii) specific adaptation to hot air popping method. Hence, when breeders evaluate popping ability of different genotypes, they should consider the method, depending on the way consumers will do the popping. The study of relationship between traits showed that popping expansion volume and seed yield was positively and significantly correlated. Nevertheless, the relationship between seed yield and popping expansion volume was weak. Popping expansion volume was negatively and weakly correlated with most secondary traits except kernel aspect and number of unpopped kernels. The direct effects of kernel aspect score on popping expansion volume were large and negative. Other traits showed small direct and indirect effects on popping expansion volume. Traits including days to anthesis, ear prolificacy and ear aspect exhibited large direct effects on seed yield. Indirect and direct effects of other traits on seed yield were small. Relationship among several secondary traits was small. The results obtained showed that selection for high seed yield will not negatively impact popping expansion volume and vice versa, therefore, popping expansion volume and seed yield can be improved concurrently. Overall, indirect effects of secondary traits on seed yield and popping expansion volume were small; this supported the focus on direct selection of these traits to improve seed yield and popping ability. Based on the study of genetic diversity and variability, inbred lines showed large genetic variation and high heritability for 18 traits. Phenotypic and genetic coefficient of variation was high in seven and six traits, respectively. A large percentage of genetic advance was recorded in 11 traits. Dendogram derived from phenotypic data grouped the inbred lines into four to seven clusters depending on heritability. Dendogram produced from 22 SSR markers grouped inbred lines into five clusters. Overall, the study showed that, maximum popping ability of inbred lines is dependent on the method used. Simultaneous improvement of seed yield and popping expansion volume is possible through selection of inbred lines combining both high popping expansion volume and seed yield. Improvement of the two traits should be based on selection for traits with large direct effects. The magnitude of genetic diversity among the inbred lines was large; therefore, distant inbred lines can be selected as parents and crossed to develop new varieties that are locally adapted. Above all, the results have implications for the methods which would be used to process popcorn by consumers especially in developing rural communities. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

The overriding objective of this study was to induce genetic variation in Vernonia (Vernonia galamensis variety ethiopica) using ethylmethanesulfonate (EMS) and select mutants for subsequent selective breeding. Vernonia is an underutilised, potential novel oilseed crop with multiple applications in industry mostly due to the production of naturally epoxidised vernolic acid oil. Commercial cultivation of vernonia is significantly hampered by non-uniform seed maturity, tall plant height, seed shattering and lack of appropriate technologies for mechanical harvesting, seed threshing and cleaning. Mutations of a single or few genes possessing target traits are invaluable in crop improvement programs. Chemical mutagenesis using EMS is an important, affordable and effective method to induce random useful genetic mutations in crop plants. Ethylmethanesulfonate mutagenesis has previously been reported to affect various agronomic traits, induce a wide variety of phenotypic mutations and alter both seed oil content and fatty acid profile on several crops. The objectives of this study were: (i) to determine an optimum EMS treatment combination i.e. exposure duration, temperature and dose that would enable 50-60% germination at minimum days to emergence in selected V. galamensis var. ethiopica lines (Vge-1, Vge-4, Vge-7 and Vge-10), (ii) to induce genetic variation using predetermined optimal treatment conditions and select mutants in V. galamensis variety ethiopica lines (Vge-1 and Vge-4) and (iii) to evaluate oil content and fatty acid compositions among seeds of chloroplast mutants, EMS treated seeds and untreated controls of Vge-1 and Vge-4. Before any mutation is administered in plants, it is important that the optimal mutation dose is determined. The lethal dose 50 (LD50) was the standard used in this study to find optimal treatment conditions. Significant interactions (P<0.001) existed between EMS, line, time and temperature with respect to days to 50% emergence, germination percentage and seedling height. Optimal days to 50% emergence (10-12 days) and germination (50- 58%) was achieved for Vge-1, Vge-7 and Vge-10 when treated with 0.372% EMS at 350C for 1 hour treatment. The optimal treatment combination for Vge-4 was 0.372% EMS at 32.50C for 2hr. The treatment combinations that yielded optimum results in the tested lines were utilized to induce large scale mutations in V. galamensis to select target mutants in the field. Large scale mutation was conducted using the observed optimal treatment conditions. Ethylmethanesulfonate mutagenesis significantly delayed days to head formation, days to flowering and days to maturity on both lines. Delays in days to emergence were only significant in Vge-4. EMS treatment also significantly reduced germination percentage, number of seeds per head, number of fertile plants, plant height and plot yield for both Vge-1 and Vge-4. Thousand seed weight significantly increased in treated seeds of the two lines. Chlorophyll mutants were observed for tested lines associated with high count of sterility for both lines. Ethylmethanesulfonate successfully induced phenotypic mutation in selected vernonia lines, however at this stage the effect of mutation on vernonia seed oil content and fatty acid was unknown. Liquid gas chromatography method was employed for oil and fatty acids analysis. In Vge-1, significant differences were observed in composition of linoleic and oleic acid due to the mutagenesis. Significant increases in linoleic and oleic acid composition were found in chloroplast mutants due to EMS mutagenesis. No significant differences were detected in fatty acid compositions in Vge-4 after the EMS treatment. Differential responses were observed when lines were compared at various EMS mutation levels showing significant effect on vernolic, linoleic and oleic acids compositions. In both lines no differences were detected on seed oil content, palmitic acid, steraic acid and arachidic acid compositions after the treatment. Oil content significantly and positively correlated with vernolic acid for Vge-1 (P<0.001; r= 0.898) and Vge-4 (P<0.05; r= 0.65). Vernolic acid significantly and negatively correlated with other fatty acids. The study found that EMS mutagenesis significantly changed the oleic acid and linoleic acid compositions in vernonia. However, the oil content and vernolic acid composition were not significantly affected by EMS treatment. This study established that EMS was successful in inducing genetic variation (in agronomic traits, seed oil content and fatty acid composition) in the two tested lines of V. galamensis. Data from a single planting generation is insufficient to conclude fully on the effect of EMS on V. galamensis; therefore it is highly recommended that further multigenerational studies should be conducted with an increased number of testing lines from a wide range of environmental backgrounds. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

The major objectives of this study were to analyze the spatial and temporal distribution of starch branching enzyme (SBE) activity in wheat (Triticum aestivum L. cv. Fielder), to clone and characterize Sbe cDNA and to analyze the expression of genes encoding the SBE isoforms. An assay based on SBE-mediated unprimed synthesis of á-1,4 glucan by phosphorylase a was standardized to detect SBE activity in the protein extracts of wheat tissues. Analysis of SBE activity in the various parts of a wheat plant revealed highest activity in developing kernels. Within a kernel, the embryo axis exhibited higher SBE activity than either the endosperm or scutellum. During kernel development, SBE activity was highest in kernels 10 days post-anthesis (DPA). As the kernels matured beyond 10 DPA SBE activity decreased. Kernel dry weight, starch and amylose concentration increased rapidly until 20 DPA whereas the moisture concentration decreased during this period. Quantitative image analysis of starch granules suggested two distinct granule types (type A and type B that varied in size and shape) were present in kernels after 15 DPA. Image analysis of starch granules isolated at the different stages of kernel development suggested that granules formed immediately after anthesis developed as type A granules while the type B granules were initiated at 12 to 15 DPA. The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to isolate partial cDNA that corresponded to Sbe1 and Sbe2 transcripts expressed in wheat kernels. Northern blot analysis, using the isolated Sbe1 and Sbe2 cDNA detected two transcripts of 4.9 and 2.8 kb in kernels and a single transcript of 2.8 kb in leaves and roots. The 2.8 kb Sbe transcript detected in kernels corresponded in size to that of Sbe transcripts reported from other plants. However, the 4.9 kb transcript detected in wheat kernels seems to represent a unique Sbe transcript. During kernel development, Sbe1 and Sbe2 genes were differentially expressed. Northern blot analysis also revealed that 4.9 and 2.8 kb Sbe1 transcripts were expressed in kernels of three hexaploid wheat cultivars, two tetraploid wheat cultivars and in a barley cultivar. A cDNA library constructed from 12 day old kernels was screened to isolate full length Sbe1 and Sbe2 cDNA clones. The longest clone isolated using the Sbe1 cDNA probe contained a truncated cDNA that represented the 4.9 kb transcript expressed in wheat kernels. RT-PCR analysis suggested that the 4.9 kb transcript was formed as a result of duplication of Sbe1 mRNA sequences. A full-length cDNA (2970 bp) that corresponded to the 2.8 kb Sbe2 transcript expressed in wheat kernels was also isolated. The translated region of the cDNA predicted a 823 amino acid primary product with a molecular mass of 91.4 kDa. The isolated cDNA clones were able to restore BE activity in BE deficient E. coli indicating that the isolated cDNA coded for a functional BE. Southern blot analysis suggested that the Sbe1 and Sbe2 transcripts were encoded by more than one gene.

Dry bean (<i>Phaseolus vulgaris</i>) is currently being introduced for rainfed production in the Dark Brown soil zone in Saskatchewan. Insufficient water is one of the major factors limiting crop production in this soil zone. Ten pinto bean genotypes (Othello, Agate, GH196-2, 6315, 5325, Earliray, Fiesta, ISB82-354, UI 111 and Nodak) were exposed to drought stress in the field to study their rooting pattern under drought stress. Three pinto bean genotypes (Othello, Agate and GH196-2) with an extensive root system in the deeper soil layers and three (Earliray, Fiesta and ISB82-354) with a less extensive root system were exposed to drought stress and nonstress conditions in the growth room and in the field to study the relationship between rooting pattern and seed yield. In addition, three indeterminate pinto bean genotypes (Othello, Nodak and Fiesta) and three determinate genotypes (Agate, Agassiz and Earliray) were exposed to a soil moisture gradient to study the effects of soil moisture level on seed yield and other agronomic traits. Othello, Agate and GH196-2 had an extensive root system in the deeper soil layers, whereas Earliray, Fiesta and ISB82-354 had a less extensive root system in the deeper soil layers. An extensive root system in the deeper soil layers was associated with increased soil moisture depletion at those depths. Shoot dry mass, total root dry mass, mean root length density and root:shoot ratio were the same for the ten pinto bean genotypes. Pinto bean genotypes with an extensive root system (Othello, Agate and GH196-2) in the deeper soil layers had higher seed yield compared to genotypes with a less extensive root system (Earliray, Fiesta and ISB82-354) in the deeper soil layers in the field and in the growth room. Due to insufficient drought stress in the field, the rooting pattern of the six pinto bean genotypes was the same under irrigation and rainfed conditions. In the growth room, pinto bean genotypes with an extensive root system showed a stronger recuperative ability after a severe drought stress compared to genotypes with a less extensive root system. Root traits were positively correlated with seed yield under adequate soil moisture or where drought stress was relieved before maturity. Soil moisture deficit reduced number of pods per plant, plant height, seed weight, seed yield and seed nitrogen concentration of both determinate and indeterminate pinto bean genotypes. Indeterminate pinto bean genotypes had, on average, higher mean seed yield and showed a greater seed yield response to increasing soil moisture availability compared to determinate genotypes. However, the difference in seed yield of the two groups was small under high drought stress, except in the case of one very early maturing determinate genotype.

In order to reduce the vulnerability of wheat production to drought, a calibrated and validated CERES Wheat crop simulation model was used to predict wheat yields on major soil textural groups using historical weather data at Swift Current, Saskatoon and Melfort. Yields were predicted using a run-out technique which involved the use of actual weather data to the prediction date and historical weather data from 1960 to 1990 for the remainder of the growing season. Yield predictions were made at five Julian dates during the crop calendar and these dates coincided with crop emergence, terminal spikelet initiation, end of the vegetative growth, heading and start of grain filling. Three sample years were used as case studies to test the applicability of the run-out method in making yield predictions. Sample base years were those with the lowest, medium and highest yields between 1960 and 1990 and these were selected from ranked yield values using quartiles. Test years were termed base years and weather files that were joined with the test years were run-out years. Each base year had 30 run-out years (1960-1990) and the mean of each run-out year was compared with the observed yield at the end of the season. Run-out yields for each base year were summarised as simple probability distributions so that yields exceeding certain values could be selected. Run-out yields at five prediction dates were found to be in close agreement with observed yields at the end of the growing season. To account for the variability in yields that can be found between places within the same climatic zone, simulated yields were re-classified by soil type and water stress level. These modifiers (soil type and water stress level) showed that chances of getting high yields diminish from Melfort to Swift Current at all prediction points due to the high variability of yield factors. Yield predictions that were made as above suggested that if historical weather records are combined with available weather data during the growing season, a good indication of yields can be obtained ahead of the harvest time and this could allow producers and those in the agri-business to decide on alternative actions of minimizing losses when prospects of getting a good yield are poor.

Some researchers have proposed that carbon isotope discrimination (CID) be used to indirectly select for grain yield and transpiration efficiency in C₃ plants. To determine the effectiveness of CID in indirectly selecting for grain yield and transpiration efficiency, ten diverse lentil (<i>Lens culinaris Medikus</i>) genotypes, ten diverse wheat genotypes (eight spring wheat (<i>Triticum aestivum </i>L.) and two durum wheat (<i>Triticum turgidum</i> L.)), and ten diverse canola (<i>Brassica napus L</i>.) genotypes were grown in a greenhouse at 80, 50, and 30% field capacity and in the field at several locations in Saskatchewan in 1992 and 1993. In the greenhouse, above ground dry matter was harvested at 80% flowering, and data collected on water use, transpiration efficiency, weight of dry matter at flowering, and CID on dry matter at flowering analyzed. In the field, samples were collected from leaves at flowering, leaves at maturity, and kernels at maturity, and analyzed for CID. In all species in the greenhouse, genotypic differences in CID were observed under all three water regimes. For lentil and wheat, the 80% field capacity water regime provided the largest differences in CID, whereas the 30% field capacity water regime provided the largest differences in CID for canola. In all three crops, CID and transpiration efficiency were independent under all three water regimes, or when averaged across water regimes and years. The correlation between CID and dry matter at flowering was inconsistent across water regimes and years. In the field, genetic variability for CID at different growth stages and in different plant organs was observed in all three species. The genotype by environment interaction for CID was low compared to that for grain yield. In addition, the correlations between grain yield and CID in lentil and spring wheat were positive, but inconsistent across locations and years. The broad-sense heritability for grain yield was greater or similar to the broad-sense heritability of CID measurements. These results suggest that under these conditions CID could not be used effectively to indirectly select for grain yield in lentil, spring wheat, or canola.

Recent research has focused on the molecular characterization of null waxy (Wx), 'Wx-A1b, Wx-B1b', and 'Wx-D1b', alleles that produce no detectable Wx proteins in the endosperm starch of allohexaploid wheat (<i>Triticum aestivum</i> L.; 2n = 6x = 42; AABBDD). The major objectives of this thesis were to (1) isolate and characterize a Wx wheat cDNA and (2) to identify aberrant 'Wx' transcripts encoded by the null 'Wx-A1b' allele of CDC Wx2, a waxy hexaploid wheat line, which result in an absent Wx-A1 protein (~59 kD). In the first study, a cDNA library prepared from developing wheat kernels (cv. Fielder) was screened using a homologous PCR-digoxigenin labeled wheat cDNA probe. A 2.2 kb cDNA clone denoted GBSSIMMI (Accession no. Y16340) was sequenced and identified as encoding a Wx-D1 protein. The deduced amino acid sequence showed 94% similarity with a wheat Wx-A1 peptide, 96% similarity with a wheat Wx-B1 peptide, and 100% identity with two wheat Wx-D1 peptides. A 33-nucleotide deletion, encoding 11 amino acids (AMLCRAVPRRA), was detected within the GBSSIMMI cDNA relative to a previously isolated wheat cDNA (accession no. X57233). Complementation analysis using a glycogen synthase deficient 'E. coli' strain and an 'in vitro' starch synthase assay did not indicate that GBSSIMMI encoded a functional Wx-D1 protein. In the second study, two sister lines CDC Wx2 and CDC Wx6 were obtained by crossing lines Bai-Huo (carries null 'Wx-D1b' allele; lacks Wx-D1 protein) and Kanto 107 (carries null 'Wx-A1b' and -'B1b' alleles; lacks Wx-A1 and -B1 proteins). Waxy protein profiling, amylose concentration determinations, Northern blot analysis, and reverse transcriptase PCR (RT-PCR) analysis were conducted. Ten RT-PCR derived cDNA clones were selected from each genotype and characterized by DNA sequencing analyses. The waxy phenotype of CDC Wx2, lacking Wx-A1, -B1, and -D1 proteins and possessing a reduced amylose concentration ~4%), was associated with dramatically reduced levels of a 2.4 kb 'Wx' transcript when compared to the higher levels in a wildtype control line. DNA sequencing of clones from Kanto 107 and CDC Wx2 characterized two types of aberrant 'Wx' transcripts, one containing intron 1 and another containing introns 1 and 4. Intron 1 in both types of aberrant 'Wx' transcripts contained a premature stop codon which resulted in the translation of a truncated Wx protein ~4 or 11 kD). Analysis of CDC Wx6, lacking Wx-B1 and -D1 proteins and possessing a reduced amylose concentration (~14%) failed to reveal aberrant ' Wx' transcripts, suggesting that the RNA defects in this study were not responsible for the absence of the Wx-B1 or -D1 proteins. Thus, the aberrant Wx transcripts were encoded by the null 'Wx-A1b' allele. The presence of a premature stop codon in the 'Wx' transcripts encoded by the null 'Wx-A1b' allele explained the absence of the ~59 kD Wx-A1 protein in CDC Wx2 and its parental line Kanto 107.

No abstract available. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Groundnuts (Arachis hypogaea L.) are an important subsistence and cash crop for smallholder farmers in Southern Africa. They require well drained light textured soils. However, most light textured soils are acidic and inherently infertile, and therefore require supplementary nutrients and amelioration with lime. In addition to application of a basal fertilizer, groundnut production also requires Ca. This increases the inputs required to produce the crop, particularly for smallholder farmers. The study examined two options for smallholder farmers, outside the classical lime application, for ameliorating soil acidity, i.e., evaluating the response of different groundnut genotypes for tolerance to soil acidity and low-cost liming alternatives. Initially ten groundnuts genotypes were screened for tolerance to soil acidity. Following this, three genotypes classified as tolerant and susceptible were used to evaluate the effect of high acid saturation on germination, emergence and seedling establishment. Thereafter, selected cultivars were used to compare calcium silicate, as an alternative to dolomitic lime, for ameliorating soil acidity and supplying calcium to developing pods. All three studies were conducted under controlled conditions: 25 ± 5°C and 20 ± 3°C day/night temperatures, 65% RH. Results measured as plant height, leaf area, yield, concentration and uptake of selected macro-and micro-nutrients showed that different groundnut genotypes differed in their response to soil acidity. Genotypes like Billy, Selmani, Rambo and JL 24 had low Al uptake and high Ca and P uptake and were classified as tolerant to acidity. In addition, these genotypes also had a higher leaf area and high number of nodules compared with Anel, Harts, Sellie, RG 784 and Robbie. With the exception of JL 24 all other tolerant genotypes (Billy, Selmani and Rambo) were large seeded. In the early establishment stage especially, root development was susceptible to soil acidity, but Rambo appeared to perform better than Jasper and Harts. Calcium silicate reduced soil acid saturation and provided enough calcium for pod development, suggesting that it may be used as an additional source of calcium. Soil acidity increased grain protein concentration and reduced its oil content, however, amelioration with either lime source reversed this trend. Thus, growing groundnuts in acid soils has implications for the commercial value of the product in terms of oil or protein supply. Overall, the study suggests that a combination of application of a cheap liming source like calcium silicate and growing tolerant cultivars, like Rambo, Billy and JL 24 might provide a window of opportunity for smallholder farmers to produce groundnuts possibly with only a fraction of the costs associated with ameliorating soil acidity. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Cowpea (Vigna unguiculata L.) is an important legume, especially in the hot, dry tropics and subtropics of sub-Saharan Africa. It has been widely reported to be drought tolerant. Cowpea is a highly nutritious, multi-purpose crop, used as a leafy vegetable and grain legume with potential to contribute to food security in marginal areas. However, the crop is still classified as a neglected underutilised species; legume research focus has been mainly devoted to established legumes such as common bean and soybeans. There is a need to collect empirical information on cowpea which could be used to advise farmers on management strategies. This study evaluated cowpea responses to water stress under controlled and field conditions. Initially, two cowpea varieties (Brown and White birch) were evaluated for seed quality using the standard germination that was laid out in a completely randomised design and each variety was replicated for times. Electrolyte conductivity test was also performed under laboratory conditions. Thereafter, a pot trial was conducted to evaluate cowpea response to water stress imposed at different growth stages under varying growth temperatures. The pot trial comprised three factors: temperature [High (33/27ºC), Optimum (27/21ºC) and Low (21/15ºC)], water regimes (no stress, terminal stress, intermittent stress – vegetative and intermittent stress - flowering) and cowpea varieties. Lastly, a field trial was conducted to evaluate cowpea production as well as the effect of sequential leaf harvesting on yield under irrigated and rainfed conditions. The field trial was laid out as a split-plot design, with water regime (irrigation vs. rainfed) as main factors, cowpea varieties as sub-factor and sequential harvesting (no harvest, harvested once and harvested twice), replicated three times. All treatments were arranged in a randomised complete block design. Results of the initial study showed that germination capacity and vigour of cowpea varieties were significantly different (P < 0.001). White birch had higher electrolyte leakage than Brown birch. Pot trial results showed that cowpea growth (leaf area, leaf number and plant height) was vigorous in the high temperature regime compared with optimum and low temperature regimes. Chlorophyll content index was higher under high temperature relative to optimum and low temperature regimes, respectively. Under low and optimum temperature regimes, cowpea growth was stunted; cowpea failed to flower and form yield. Whereas, under high temperature regime, cowpea growth was vigorous hence flowered and formed yield. Vegetative growth was more sensitive to water stress than flowering stage. Terminal stress and stress imposed during flowering resulted in increased proline accumulation relative to no stress and stress imposed during vegetative growth. Harvest index was lower when water stress was imposed during vegetative relative to flowering stage. Field trial results showed that cowpea growth was sensitive to water stress. Plant height, leaf number, chlorophyll content index and stomatal conductance were lower under rainfed relative to irrigated conditions. Sequential harvesting of leaves had no significant effect on cowpea yield. It is concluded that tropical temperature conditions are most suitable for cowpea production; the controlled environment study showed best crop performance under 33/27ºC. In the context of varieties used for the present study, vegetative growth was the most sensitive stage to water stress. Cowpea performed better under rainfed relative to irrigated conditions with respect to yield formation. Low temperature was found to be more limiting to cowpea growth, development and productivity compared with water stress. Whereas, under high temperature conditions, water stress was more limiting to plant growth and productivity. White birch may be used as a dual purpose crop due to its ability to produce reasonable grain yield regardless of defoliation. / Thesis (M.Sc.Agric)-University of KwaZulu-Natal, Pietermaritzburg, 2012.