In Limpopo Province of South Africa, poor soil fertility and low crop yields are serious problems facing resource poor smallholder farmers. A survey of over 60 farmers in 2 villages (Gabaza and GaKgoroshi) found that most of the smallholder farmers were women (68%), elderly (50% above 68 years of age) and had not attended school or only attended up to the primary level (80%). Very few farmers kept livestock (usually in small numbers) and most grew cereal and legume crops (on 1ha of land) for home consumption and livestock feed, with legumes being planted on 13% of the land. The study showed that 80% of farmers were not fully aware of the benefits of legumes in fixing nitrogen (N) and improving yield. A field study at the survey village of Gabaza found that the application of fertiliser N and grass mulch combination and fertiliser N plus guarbean mulch significantly increased plant height and maize shoot growth at 4 and 8 weeks after planting. However, when grass mulch was without N fertiliser, there was no increase in maize growth relative to the control (0N). A farming systems simulation model (Agricultural Production Systems sIMulator - APSIM) was used to simulate this field study as well as over the long-term (1971 to 2008). Simulation analysis showed poor average maize yield (<3000 kg ha⁻ ¹) with the application of grass residues even when used with 30 kg N fertiliser. However, the application of guarbean residues as mulch with or without N fertiliser and as green manure increased maize yields to >4000 kg ha⁻ ¹. Simulation showed that the grass mulch with or without the addition of N fertiliser reduced water stress and soil water evaporation but increased N stress during the reproductive phase of the crop in most seasons. When guarbean mulch was used as green manure by itself, or mulch plus N fertiliser, N stress was reduced but water stress and soil water evaporation were increased which could have been due to faster decomposition of legume mulch as compared to grass mulch. Addition of N fertiliser reduced N stress to maize but increased water stress and soil water evaporation similar to the guarbean mulch because of high soil evaporation. APSIM analysis clearly showed the importance of N x soil water interactions in determining maize growth and yield at Gabaza. Therefore, two studies were undertaken in the laboratory in Australia to determine the dynamics of carbon (C) and N where residues of different qualities [canola (C:N 43), wheat (26), pea (9) and mucuna (14)] were applied to clay loam (Tarlee) or sandy (Waikerie) soils. In experiment 1, where residues were incorporated into the two soils, the cumulative CO₂-C evolution for the wheat and canola treatments at the end of the incubation period were fairly similar but significantly higher than for pea, mucuna and the control. In general, the application of residues increased microbial biomass C more than the control, with highest increases up to 1.48 and 1.56 mg C g⁻ ¹ soil for canola and wheat in Tarlee soil, respectively and 0.82 mg C g⁻ ¹ soil for pea in Waikerie soil. Even though the Tarlee soil showed greater C release than Waikerie soil, the C turnover from the residues between the 2 soils was not significantly different except for pea residues. Canola and wheat residues were found to immobilise N whereas N content increased in both soils with the application of legumes (pea and mucuna). In experiment 2, mucuna, pea and wheat residues were either incorporated or applied as surface mulches on Waikerie soil. Initially the CO₂-C release was higher for incorporated than mulched residues and CO₂-C released was higher for pea residues. However, at the end of the incubation more CO₂-C was released with the application of wheat residue indicating differences between residue types in the pattern of soil respiration. Microbial biomass C was higher for incorporated than mulched residue treatments; pea residue showed the highest biomass C for incorporated (0.78 mg C g⁻ ¹ soil) whereas mucuna had the highest microbial biomass (0.11 mg C g⁻ ¹ soil) treatments. The method of residue application resulted in a significant difference in C turnover between residues, with pea residue showing significant increase in C utilisation than mucuna and wheat. The pea residues, which had the lowest C:N, increased soil mineral N more than other treatments in both incorporated and mulched treatments. Lower mineralisation of N observed in residues of high C:N ratio compared to the control could be due to immobilisation of N. Therefore, understanding the nutrient dynamics of different crop residues could play an important role in the management of residues in different soil types. Based on these results it can be concluded that legume residues have the potential to improve soil fertility and crop yields in dryland farmers’ fields in Limpopo. Extension programs aimed at increasing farmers’ knowledge of the benefits of N fixation by legumes may increase their adoption and thereby improve soil fertility and maize yield. / Thesis (M.Ag.Sc.) -- University of Adelaide, School of Agriculture, Food and Wine, 2010

The maize leaf has three main axes of growth, with an asymmetric distribution of tissue types along each axis. This study focuses on three mutants, Wavy auricle in blade1-R (Wab 1-R), liguleless1-R (lg1-R) and milkweed pod1-R (mwp1-R) that disrupt axial patterning of maize leaves. Dominant Wab1 mutations disrupt both medial-lateral and proximal-distal patterning. Wab1 leaf blades are narrow and ectopic auricle and sheath-like tissues extend into the leaf blade. Previous analyses have shown that Lg1 acts cell-autonomously to specify ligule and auricle tissues. The current study reveals additional roles in defining leaf shape. The recessive lg1-R mutation exacerbates the Wab1-R phenotype; in the double mutants, most of the proximal blade is deleted and sheath tissue extends along the residual blade. A mosaic analysis of Wab1-R was conducted in Lg1 and lg1-R backgrounds to determine if Wab1-R affects leaf development in a cell-autonomous manner. Normal tissue identity was restored in all wab1/- sectors in a lg1-R mutant background, and in three quarters of sectors in a Lg1 background. These results suggest that Lg1 can influence the autonomy of Wab1-R. In both genotypes, leaf-halves with wab1/- sectors were significantly wider than non-sectored leaf-halves, suggesting that Wab1-R acts cell-autonomously to affect lateral growth. mwp1-R is a recessive mutation that specifically affects patterning of sheath tissue. Characterisation of the mwp1-R phenotype revealed that mwp1-R husk leaves and the sheaths of vegetative leaves develop pairs of outgrowths on the abaxial surface associated with regions of adaxialised tissue. In situ hybridisation confirmed that disruptions to adaxial-abaxial patterning are correlated with misexpression of leaf polarity genes. Leaf margins and fused organs such as the prophyll are most severely affected by mwp1-R. The first two husk leaves normally fuse along adjacent margins to form the bi-keeled prophyll. In the most severe cases the mwp1-R prophyll is reduced to an unfused, two-pronged structure and keel outgrowth is significantly reduced. We speculate that the adaxial-abaxial patterning system has been co-opted during evolution to promote outgrowth of the keels in normal prophyll development. The results of this study place Mwp1, wab1 and Lg1 in a network of genes that regulate leaf polarity and axial patterning.

In the Shoot Apical Meristem (SAM) the position at which leaf primordia arise on the periphery, and their subsequent differentiation, have been shown to be (at least in part) to be directed by genetic programs of development. A candidate gene associated with this regulation is TERMINAL EAR 1 (TE 1) a maize gene identified by the irregular phyllotaxy of its mutant lines. Unlike most other genes associated with meristem function, TE 1 is a novel RNA binding gene of the RRM type. It has been shown to have orthologues in a variety of plants including Arabidopsis thaliana as well as unicellular eukaryotes including MEI2, a gene whose product is associated with the regulation of meiosis in Schizosaccharomyces pombe. In order to more fully understand TE1's role, a functional characterisation of two of the so-called Mei2-like genes was undertaken in the model plant A. thaliana. These genes are called Terminal Ear-Like 1 and 2 (TEL1 and TEL2). Constitutive overexpression of the cDNA of TEL2 using the Cauliflower Mosaic Virus 35S promoter (CaMV35S) revealed a phenotype involving an apparently prolonged vegetative phase. However this was only observed in a limited number of lines of the total screened, and the next generation did not reiterate this phenotype. These difficulties were overcome using the LhGpOP construct system for ectopic misexpression in specific domains as well as inducible ubiquitous expression. Ectopic expression of either TEL cDNA is shown to lead to a pleiotrophic spectrum of phenotypes, which in general, were associated with reduced determinant development outside the apical meristems and as well as a delayed overall developmental progression. This provided some evidence that the normal function of TEL genes within the apical meristems is the repression of differentiation associated with the regulation of plant growth and architecture.

The South Burnett region of Queensland is Australia's most important rainfed peanut (Arachis hypogea L.) production area. It also produces a considerable amount of cereal and grain legume crops. The cropping soils of the region are red, acid to neutral, clay loams that are classified as Ferrosols (Australian Soil Classification). Over 50 years of cropping on these soils has resulted in severe depletion of nutrient reserves, particularly potassium (K). In addition, the remaining K is predominantly confined to the surface 10 or 15cm of the soil profile, a feature commonly refered to as nutrient stratification. Dry periods during the summer cropping season are common due to the highly variable, summer-dominant rainfall pattern of the South Burnett. As topsoil dries out, crops forage for moisture and nutrients from lower in the soil profile where K reserves are smaller. It is therefore suspected that the combination of dry periods and stratified K reserves have resulted in an increasing incidence of K deficiency symptoms in summer crops. To investigate these issues, K relations of Ferrosols of the South Burnett were studied using soils from two representative sites. The pools of soil K that are important to crop growth in Ferrosols, and their interaction was examined through fractionation of soil K pools, and determination of quantity/intensity relationships, charge characteristics and clay mineralogy, and a leaching column study. A rapid K uptake period was identified for peanut and the effect of profile distribution and soil moisture during this period on K accessibility was studied in a divided column experiment. Finally, on-farm trials were used to evaluate commercial-scale options for improving K distribution in field profiles. It was found that the immediately available exchangeable K pool in these soils was the most important source of soil K, and was poorly buffered by slowly available non-exchangeable K. However the leaching column study revealed that K was preferentially adsorbed onto soil cation exchange sites, displacing calcium (Ca) and magnesium (Mg) ions, and therefore was not susceptible to vertical movement within the soil profile. These observations helped to explain the development of stratified K profiles in these soil types. Peanut (cv. Streeton) was found to take up most of its K requirement between 25-70 days after planting. The divided column study showed that profile distribution, and topsoil iv moisture content during this rapid K uptake period, were able to affect the ability of peanut plants to access K. Plants that grew in low K soil, or where soil was dry at the site of K supply, had reduced access to K. However, improving access to K did not result in improved growth, but rather in a significant reduction in dry matter (DM) production, apparently due to interference in the availability of other nutrients, possibly phosphorus (P), magnesium (Mg) or boron (B). Field studies showed that application of K and profile inversion improved K uptake and DM production of various crop species. However, in most instances improved K uptake and DM production was not reflected in increased yield. It was suggested that a combination of agronomic factors, seasonal conditions and crop type prevented the expression of yield responses to improved K nutrition and these influences need to be understood. The findings of this project have important consequences for nutrition of crops grown on Ferrosols in the South Burnett region. Surface applied K cannot be expected to increase exchangeable K in the subsoil unless it is incorporated to depth. Similarly, band applied K will remain close to the site of application as a result of only limited vertical or lateral movement. This may affect the ability of roots to access band applied K. The ability of surface applied K to displace Ca and Mg from soil exchange sites may have negative implications for the Ca nutrition of developing peanut pods. On the other hand, it could present an opportunity for the movement of Ca into deeper soil layers to address the amelioration of acid subsoils. The unexplained negative responses to potassium chloride application and apparent effect on P, Mg or B nutrition need to be investigated.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 3 uppsatser.

Thesis (Ph. D.)--University of Wisconsin, 1974. / Vita. Description based on print version record. Includes bibliographical references (leaves 414-419).

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / The use of near infrared (NIR) hyperspectral imaging and hyperspectral image analysis for distinguishing between whole maize kernels of varying degrees of hardness and fungal infected and non-infected kernels have been investigated. Near infrared hyperspectral images of whole maize kernels of varying degrees of hardness were acquired using a Spectral Dimensions MatrixNIR camera with a spectral range of 960-1662 nm as well as a sisuChema SWIR (short wave infrared) hyperspectral pushbroom imaging system with a spectral range of 1000-2498 nm. Exploratory principal component analysis (PCA) on absorbance images was used to remove background, bad pixels and shading. On the cleaned images, PCA could be used effectively to find histological classes including glassy (hard) and floury (soft) endosperm. PCA illustrated a distinct difference between floury and glassy endosperm along principal component (PC) three. Interpreting the PC loading line plots important absorbance peaks responsible for the variation were 1215, 1395 and 1450 nm, associated with starch and moisture for both MatrixNIR images (12 and 24 kernels). The loading line plots for the sisuChema (24 kernels) illustrated peaks of importance at the aforementioned wavelengths as well as 1695, 1900 and 1940 nm, also associated with starch and moisture. Partial least squares-discriminant analysis (PLS-DA) was applied as a means to predict whether the different endosperm types observed, were glassy or floury. For the MatrixNIR image (12 kernels), the PLS-DA model exhibited a classification rate of up to 99% for the discrimination of both floury and glassy endosperm. The PLS-DA model for the second MatrixNIR image (24 kernels) yielded a classification rate of 82% for the discrimination of glassy and 73% for floury endosperm. The sisuChema image (24 kernels) yielded a classification rate of 95% for the discrimination of floury and 92% for glassy endosperm. The fungal infected and sound whole maize kernels were imaged using the same instruments. Background, bad pixels and shading were removed by applying PCA on absorbance images. On the cleaned images, PCA could be used effectively to find the infected regions, pedicle as well as non-infected regions. A distinct difference between infected and sound kernels was illustrated along PC1. Interpreting the PC loading line plots showed important absorbance peaks responsible for the variation and predominantly associated with starch and moisture: 1215, 1450, 1480, 1690, 1940 and 2136 nm for both MatrixNIR images (15 and 21 kernels). The MatrixNIR image (15 kernels) exhibited a PLS-DA classification rate of up to 96.1% for the discrimination of infected kernels and the sisuChema had a classification rate of 99% for the same region of interest. The The iv sisuChema image (21-kernels) had a classification rate for infected kernels of 97.6% without pre-processing, 97.7% with multiplicative scatter correction (MSC) and 97.4% with standard normal variate (SNV). Near infrared hyperspectral imaging is a promising technique, capable of distinguishing between maize kernels of varying hardness and between fungal infected and sound kernels. While there are still limitations with hardware and software, these results provide the platform which would greatly assist with the determination of maize kernel hardness in breeding programmes without having to destroy the kernel. Further, NIR hyperspectral imaging could serve as an objective, rapid tool for identification of fungal infected kernels.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2008. / South Africa as well as other grain producing and exporting countries’ grading systems strongly relies on hectolitre mass (HLM) as a guide to grain quality. It is known that these countries use either one of two types of HLM equipment. These devices consist of either a funnel or a cylindrical device (chondrometer) with a measuring cylinder of known volume underneath which is then filled with grain in a controlled manner. Subsequently the HLM devices from Australia, Canada, France, Germany, South Africa, the United Kingdom (UK) and the United States of America (USA) were compared using impurity free mixed wheat, single South African cultivars as well as maize samples. Very little variation in HLM measurements within the HLM devices was observed with intra-class correlation (ICC) agreement values close to one. Comparing the actual HLM values obtained with the respective devices showed that the results obtained with the Australian device was significantly (P < 0.05) higher, and those obtained with the South African devices significantly (P < 0.05) lower compared to the other devices. As would be expected the devices showed better overall ICC agreement when the HLM tests were performed with the single cultivar samples (ICC agreement = 0.762) as opposed to the mixed wheat samples (ICC agreement = 0.523). However, the HLM values obtained with all the devices correlated well with each other (ICC consistency >0.90) indicating that correction factors can therefore be developed to convert the HLM results between devices. When ten South African devices were compared statistical differences were observed, but the overall ICC agreement (0.975) and consistency (0.993) values indicated that the differences would not be significant in practice. Hectolitre mass determinations performed on samples prior to and after impurities have been removed revealed that the removal of impurities resulted in a significant (P < 0.05) increase in HLM. The effect of operator was shown to be significant (P < 0.05) when operators with three levels of competency, i.e. skilled, semi-skilled and unskilled, were investigated. The effect of wet and dry cycles on the HLM measurements was investigated and the results showed that wetting and drying could change the integrity of the wheat. Moisture correction factors cannot be applied to convert the HLM values of grain that underwent moisture changes as different samples responded differently to the moisture treatments. Comparing the respective devices with mixed maize samples (impurities not removed) very little variation in HLM measurements within each device was observed. The comparison of the devices revealed that the HLM measurements obtained with the Australian and French devices were significantly (P < 0.05) higher and that obtained from the Canadian device significantly (P < 0.05) lower compared to those obtained with the other devices. Again it was shown that the devices correlate well (ICC consistency > 0.97) and that correction factors can be applied to convert HLM results between devices. An alternative to the use of correction factors could be the replacement of the South African device with the German device for both wheat and maize. The removal of impurities from the maize samples significantly (P < 0.05) increased the HLM values. Therefore, it is likely that correction factors can be used to convert HLM values of maize samples before and after removal of impurities.

Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Maize is an important crop for both human and animal consumption. Maize kernel texture (kernel hardness) is an important quality trait for many sectors in the South African maize industry, where a harder texture is desired. Both total protein content and the main storage proteins, zein, have been associated with kernel texture. The zein profiles of South African white maize hybrids, from a breeding program, grown at three localities together with their respective inbred parent lines were evaluated to determine the difference in zein expression. For only the hybrids, total protein content, zein content and degree of hardness (kernel texture) was determined to establish possible relationships. Zein consists of four main classes, α-, β-, γ-, and δ-zein, which can further be divided into sub-classes. Zein was characterised using matrix-assisted laser desorption ionisation time-offlight mass spectrometry (MALDI-TOF MS) after optimisation of the zein extraction and matrix preparation procedures. Two matrices [2-(4-hydroxyphenylazo)benzoic acid (HABA) and α- cyano-4-hydroxy-cinammic acid (CHCA)] and three pH levels (<1.5, 1.7 and 2.9) for matrix solutions were investigated. Two solvent concentrations (50% and 70% acetonitrile (ACN) were also investigated. Parallel to this investigation, a zein extraction procedure was optimised. Zein was extracted from non-defatted (NDF) and defatted (DF) maize meal at ambient temperature and 60°C and meal with different particle size distributions. Particle size of maize meal did not influence the quality of spectra. Regardless of matrix conditions used, zein extracted at 60°C from NDF meal produced spectra with a low signal-to-noise (S/N) ratio. When only HABA was included (pH<1.5), not all γ-zein sub-classes were observed. This was also true for zein extracted at ambient temperature from NDF and DF meal. Good S/N ratios for all zein classes were obtained when zein was extracted from NDF meal at ambient temperature using a matrix solution containing both matrices in 70% ACN at pH 2.9. MALDI-TOF MS provided accurate detection and good profile resolution for zein characterisation. Spectral profiles of hybrids were a combination of their respective inbred parent lines. Zein proteins were quantified using reverse-phase high performance liquid chromatography (RP-HPLC). Total protein content was determined and kernel texture assessed using a particle size (PSI) method. Significant (P<0.01) differences were observed for total protein content and degree of hardness between certain hybrids as well as average values for localities. Correlations and principal component analysis indicated that hybrids with a higher protein and total zein content had a harder kernel texture. The β- and γ-zein contents also correlated positively with kernel hardness. However, when expressed as percentage of total zein the opposite was observed. Collectively the α-zeins and most individual α-zeins correlated positively with hardness. Scanning electron microscopy micrographs showed differences between the floury endosperm of harder and softer maize kernels; illustrating starch types (amylose and amylopectin) should also be analysed in future hardness studies. The correlations obtained were not strong (r<0.6) and the variation explained by first two principal components was low. Other maize constituents, more hardness measurements should be considered in future studies to improve this. / AFRIKAANSE OPSOMMING: Mielies is a belangrike gewas vir beide mens- en dierlike inname. Mieliepittekstuur (pithardheid) is ‘n belangrike kwaliteitseienskap vir baie sektore in die Suid Afrikaanse mielieindustrie, waar ‘n harder tekstuur verlang word. Beide totale proteïeninhoud en die hoof opbergingsproteïen, zein, is al geassosieer met pittekstuur. Die zein profiele van Suid- Afrikaanse witmielie basters, van ‘n teel program, wat by drie lokaliteite verbou is sowel as hul onderskeie ingeteelde ouerlyne is geevalueer om verskille in zein uitdrukking te bepaal. Die totale proteïeninhoud, zeininhoud en graad van hardheid is bepaal om verhoudings vas te stel. Zein bestaan uit vier hoof klasse, α-, β-, γ-, en δ-zein, wat verder onderverdeel word in subklasse. Zein is gekarakteriseer met matriks-ondersteunende laser desorpsie ionisasie tyd-vanvlug massa spektrometrie (MBLDI-TVV MS) na die zein ekstraksie en matriks voorbereidingprosedures geoptimaliseer is. Twee matrikse [2-(4-hydroksiephenylazo)benzoë suur (HABA) en α-cyano-4-hydroksie-kaneelsuur (CHCA)] en drie pH vlakke (<1.5, 1.7 and 2.9) vir matriksoplossings was ondersoek. Twee oplossingkonsentrasies [50% and 70% asetonitriel (ACN)] is ook ondersoek. Zein ekstraksie kondisies is ook geoptimiseer. Zein is geëkstraheer van nie-ontvette (NOV) en ontvette (OV) mieliemeel by omgewings temperatuur en 60°C. Die partikelgrootte van die mieliemeel het nie die kwaliteit van spektra beïnvloed nie. Ongeag watter matrikskondisies gebruik is het zein wat van NGV meel by 60°C ge-ekstraheer is, spektra met ‘n lae sein-tot-geraas (S/G) verhouding geproduseer. As die HABA alleenlik gebruik (by pH<1.5) is, is nie alle γ-zein klasse waargeneem nie. Dit was ook waar vir zein wat by omgewings temperatuur van NGV en OV mieliemeel ge-ekstraheer is. Goeie S/G verhoudings is waargeneem met zein, ge-ekstraheer van NGV mieliemeel by omringende temperatuur, met die bebruik van beide matrikse in 70% ACN by pH 2.9. (MBLDI-TVV MS) het akkurate en goeie resolusie van profiele vir zein karateriseering verksaf. Spektrale profiele van basters was ’n kombinasie van hul onderskeie ouer lyne. Zeinproteïene is met omgekeerde-fase hoë prestasie vloeistofchromatografie gekwantifiseer. Totale proteïeninhoud is bepaal en die hardheidsgraad was bepaal met ‘n partikelgroote indeks (PGI) metode. Beduidende verskille tussen proteïeninhoud en hardheidsgraad is waargeneem tussen sekere basters sowel as gemiddelde waardes by die verskeie lokalieteite. Korrelasies en hoofkomponent analise het aangedui dat basters met ‘n hoër proteïeninhoud en totale zein ‘n harder tekstuur gehad het. Die β- en γ-zeininhoud het ook positief gekorreleer met hardheid. Alhoewel, wanneer die proteïene as persentasie van totale zein uitgedruk is, is die teenoorgestelde waargeneem. Gesamentelik het α-zein asook die meeste indivduele α-zeins positief gekorreleer met hardheid. Skandeer elektron mikroskopie mikrograwe het verskille tussen die meelerige endosperm van harder en sagter pitte aangedui; meer proteïenliggame was aanwesig in die harder pitte en die stysel was digter gepak. Dus moet stysel tipes ook in ag geneem word in toekomstige hardheidsstudies. Korrelasies wat verkry is, was nie hoog (r<0.6) nie en die variasie verduidelik deur die eerste twee hoofkomponente was laag. Ander miielie samestellende dele as ook meer hardheidsmetings moet in toekomstige studies in ag geneem word om dit te verbeter.