In Libya salinization of land and ground water is a key problem. A. saligna is one species that offers potential for growth under these conditions. Experiments were undertaken to accelerate the germination of Acacia seeds, and various pre-treatment methods were assayed. Boiling water treatment, mechanical scarification and acid improved germination and germination rate. Sowing A. saligna seeds at 30 mm depth gave greatest seedling growth from large and medium seeds whereas 20 mm was more suitable for small seeds. This study aimed to improve the establishment of Acacia saligna irrigated with saline water, plants were grown for seven weeks under greenhouse or field conditions in (Libya) either sand or soil salinized with varying applications of NaCl. Irrigation with NaCl significantly decreased plant survival and growth and concentration of Ca, Na, K, Fe and P ions in plants with 0.5 M or 1.0 M NaCl. The experiments were repeated using a naturally occurring soil amendment called ‘Zander’. Seeds of A. saligna were grown for seven weeks in both greenhouse and field trials as before but with the addition of Zander and NaCl. Zander improved plant survival and growth with salinity and increased the elements in plants (Ca, Na, K, Fe and P). Field experiments were conducted to assess the effects of saline irrigation with 1.0 M NaCl and extra water added to 0% or 10% Zander on survival and growth, consequently, seedling growth significantly decreased with increase in soil salinity. Survival and growth increased with increase in extra water. The additional irrigation water caused an increase in the uptake of Ca++ and increased the Ca++/Na+ and K+/Na+ ratio. Zander did not appear to reduce net uptake of Na+ and its transport to shoot tissues. Mg++, P, K+ and Ca++ content significantly decreased in plants in response to salinity. Possible mechanisms to avoid Na+ toxicity in A. saligna in response to salinity included increasing the supply of Ca++. Extra Ca++ applied into the medium with and without salt increased survival and growth even in the absence of Zander. Calcium increased uptake of Ca++ and increased Ca++/Na+ and K+/Na+ ratio.

Thesis (M. Sc. (Agricultural Science)) -- University of Limpopo, 2001 / Refer to document

As nitrogen (N) is a critical nutrient for plant growth, the development of synthetic N fertilisers dramatically changed agricultural production in the twentieth century. Improvement in N use efficiency (NUE) has been a focus of breeding for grain crop species, since protein is an important component of the harvested product. The study of NUE in sugarcane has lagged behind grain crops, mainly because N is not a component of sucrose, the primary product of the traditional sugarcane industry. Recently, improvement in NUE has become a focus of sugarcane breeding, due largely to environmental concerns regarding pollution from high N fertilisation, and the increasing cost of N fertilisers. This thesis aimed to gain an initial understanding of the genetic basis for variability in NUE in sugarcane. This was achieved through: (i) the screening of 168 sugarcane genotypes under limiting and non-limiting N supply in two glasshouse experiments; (ii) the mapping of marker-trait associations (MTA) for biomass and physiological traits under limiting and non-limiting N supply in a sugarcane mapping population; (iii) the analysis of expression of candidate genes encoding enzymes involved in the central processes of N assimilation and remobilisation in plants; and (iv) the mapping of candidate genes in a sugarcane genetic map. Genetic variation was identified for growth traits as well as physiological traits including %N, internal NUE (iNUE, g dry weight g-1 N) and leaf glutamine synthetase (GS) activity in a sugarcane mapping population. These traits were also analysed for linkage with genetic markers. Genetic variation in the screened genotypes was higher under limiting N supply, a finding that was reflected by the fact that marker-trait associations (MTA) for increases in iNUE were not identified under non-limiting N supply in the commercial parent of the mapping population. Contrary to findings in grain crop species, there was no link between GS activity and other traits, either through phenotypic correlations or co-location of MTA. The expression of candidate genes encoding GS, nitrate reductase (NR) and alanine amintotransferase (AlaAT) was quantified with Sequenom™ MassARRAY technology. Plants were grown under growth-limiting N supply, non-limiting N supply, or a N-pulse treatment, which consisted of growth-limiting N supply followed by non-limiting N supply 24 hours prior to sampling. Two genes, scAlaAT.d and scGS1.a, encoding AlaAT and GS respectively, were identified as non-responsive to changes in N supply, whereas scAlaAT.a, scGS1.b and scGS1.c had significantly (p<0.05) increased expression under a N-pulse, indicating an important role for these genes in the response of sugarcane to a sudden increase in N availability. The location of candidate genes associated with variation in NUE in a sugarcane genetic map were sought through restriction fragment length polymorphism (RFLP) markers. Twenty-two probes were screened, of which two generated single-dose markers, allowing the mapping of a single allele of scAspAT, encoding aspartate aminotransferase, and two alleles of scGS2, encoding plastidic GS. Because of the economic and environmental consequences of inefficient N fertiliser application, the development of sugarcane cultivars with improved NUE is essential. Since variation for NUE exists, especially in unimproved sugarcane varieties, this may be achieved through traditional breeding methods by screening existing breeding populations under limiting N supply. Additionally, an improved understanding of the genetic basis of variation for NUE in sugarcane should be pursued by further analysis of candidate gene response to changing N availability by screening widely varying cane species for differences in gene expression, enzyme activity and metabolite profiles. The further addition of candidate gene locations to sugarcane genetic maps will aid both future marker-assisted selection in breeding, and a fundamental understanding of genetic control of NUE variation. Through the development of sugarcane cultivars with improved NUE and an enhanced knowledge of the genetic control underpinning sugarcane N physiology, concerns regarding high N fertiliser applications may be mitigated and sustainability ensured.

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.

Herbicide sod suppression during pasture renovation by legume sod-seeding often results in the loss of potentially usable forage, weed encroachment, and inadequate glass-legume ratios. A study was conducted to investigate the viability of sod suppression by sheep grazing or mowing, as alternatives to herbicide, during pasture renovation with no-till seeding of red clover (Trifolium pratense L.) or white clover (Trifolium pratense L.). Sod suppression methods evaluated were: strategically timed mowing or sheep grazing to 5 or 10 cm at seeding and during legume establishment, or similarly managed mowing or sheep grazing with an additional defoliation to 5 cm the previous fall. Additional treatments included suppression by herbicide and, unsuppressed and unseeded controls. Treatments were evaluated by determining clover plant population, botanical composition, forage yield and quality. Physical (mowing or grazing) and herbicide sod suppression resulted in similar clover plant populations; clover yields tended to be higher with herbicide suppression. However, increasing the intensity of physical suppression increased clover yields. Forage quality was increased only with sod suppression by grazing or herbicide when compared with the unimproved control. Although, for grazing this was attributed to a more frequent defoliation regime and not to the renovation itself. Unlike suppression with herbicide, physical suppression did not decrease total seasonal forage yields in the renovation year when compared with controls.

Thesis (M.Tech.: Biotechnology)-Dept. of Biotechnology and Food Technology, Durban University of Technology, 2007 iv, 75 leaves / The development of transgenic plants resulted in the need to utilize the various molecular methods (e.g., ELISA, real - time PCR etc.) for the detection or analysis of the presence or absence of a specific trait in a particular plant (Bt in this study). The overall aim of this study was to optimize a half – seed extraction technique as part of a laboratory protocol for transgenic maize plants and to explore the possibility of using the following molecular techniques: horizontal isoelectric focusing, real - time PCR and ELISA, as methods for detection of the Bt trait for incorporation into the half – seed extraction protocol.

A system dynamics model is developed to study the technology adoption process (TAP) of modern agriculture input technology such as the biotechnologies. The work shows that the system dynamics approach is appropriate to integrate the different components considered in the TAP conceptual framework elaborated in this work. The conceptual framework illustrates the different system components found important in the literature, portfolio decision-making, learning, information gathering, uncertainties and economics perceptions and their involved relationships. / The model is first calibrated and validated using the case of soybeans adoption versus corn uses in Quebec from 1987 to 1998. Validation is performed through five tests, namely visual, statistical and sensitivity, modularity and extendibility are performed to show the relevancy of the approach. / The model is then applied to the case of four input biotechnology crops. Again three types of validation tests are carried out. Results show that the model predicted the shape of the curve for all application fields.

This thesis presents an investigation of two production functions (a non-linear-in-parameters and a generalized polynomial) in order to determine which function most appropriately represents the observed relationships of the components of ICM technology. Four spring barley and one spring wheat datasets were assembled from ICM field trials conducted in the Montreal region (1987-89). / A quadratic and a Mitscherlich-Baule equation were fitted to the (five) datasets and compared with respect to a number of measures of goodness of fit. One dataset was chosen for generating and graphing a three-dimensional response surface, based on the fitted equations of that dataset. The two surfaces were compared in light of expectations regarding the two equations. / The fitted equations of three of the five datasets did not produce noteworthy results. The other two datasets provided mixed results. The response surfaces provided outcomes that were contrary to prior expectations. In general graphing the response surfaces offered limited additional insight. Ultimately, this project may have been hampered by the experimental design of the field trials, those designs being oriented to results of agronomic rather than economic significance.

Thesis (Ph.D.)--University of Melbourne, School of Resource Management, Faculty of Land and Food Resources, 2006. / Typescript. Includes bibliographical references (leaves 247-274).

Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Barry J. Jacobsen. Includes bibliographical references.