Thesis (MSc. (Botany)) -- University of Limpopo, 2015 / Soybean is an important source of high quality protein and oil for both humans and animals, especially in protein formulations for pharmaceutical and nutriceutical use. This crop is adversely affected by both biotic and abiotic stresses impacting on its productivity. Soybean productivity can be improved via techniques such Agrobacterium-mediated genetic transformation. Soybean is recalcitrant and depends on suitable explants from which new shoots can be regenerated and be amenable for transformation. The goal of this study was to produce transgenic soybean plants that are tolerant to drought stress through Agrobacterium tumefaciens-mediated transformation. Multiple shoot induction on double and single coty-node explants, obtained from soybean seedlings derived from seeds germinated in vitro on Murashige and Skoog culture medium supplemented with cytokinins was studied. The effect of different concentrations of benzyladenine (1.57, 2.00 and 4.00 mg/l), and benzyladenine (2.00 mg/l) in combination with kinetin (1.00 mg/l) was tested. The results show that the double coty-node explants produce the highest number of shoots per explant, an average of 7.93 shoots on Murashige and Skoog medium supplemented with 2.00 mg/l benzyladenine. The lowest number being 1.87 shoots obtained from single coty-node explants cultured on Murashige and Skoog medium containing 4.00 mg/l benzyladenine. The single coty-node explants showed lower frequency (10–57%) of shoot induction when compared to the double coty-node explants (50–83%). The suitability of aminoglycoside antibiotics (hygromycin, tetracycline and rifampicin) for efficient elimination of Agrobacterium tumefaciens after co-cultivation was tested using a well agar diffusion assay. Co-culturing double coty-node explants with Agrobacterium containing pTF 101 vector carrying the Oryza cystatin 1 gene resulted in 76.6, 63.3 and 60.0% shoot regeneration on Murashige and Skoog shoot induction media (shoot induction medium 1, shoot induction medium 2 and shoot induction medium 3) containing hygromycin, tetracycline and rifampicin at 500 mg/l respectively. These antibiotics showed the highest zones of inhibition against pTF 101 using the well agar diffusion assay. On the other hand, 85% plant regeneration was obtained during in vivo transformation following Agrobacterium injection into seedlings. These results imply that vi both in vitro and in vivo protocols were suitable for transgenic shoot regeneration and plant establishment since all the plants continued surviving in the presence of 6.00 mg/l glufosinate-ammonium. Future work will focus on screening of transgenic plants using beta-glucuronidase and isolating the protein encoded by the Oryza cystatin 1 gene to further confirm the generation of transformed plants carrying the gene of interest.

The mechanism of drought resistance in the seedlings of Aleppo pine (Pinus halepensis) and Brutia pine (Pinus brutia) was investigated. Both species showed anatomical and morphological adaptations to conserve moisture. Aleppo pine had a thicker cuticle, fewer stomata per unit length, per unit area, and per needle than Brutia pine. A significant number of Aleppo pine stomata were sealed with a waxy layer. Brutia pine had shorter needles, smaller needle surface area, a smaller surface area-to-volume ratio, and longer main root length. The two species were similar in height growth and in the seasonal trend of total non-structural carbohydrates (reducing sugars and starch). Brutia pine had more reducing sugars and less starch in its shoots than Aleppo pine. The latter had a greater amount of total non-structural carbohydrates and starch when the seedlings were subjected to dry down moisture stress. Electron microscopy techniques were used to monitor ultrastructural changes in the chloroplasts of mesophyll cells. Aleppo pine was found to contain chloroplasts exhibiting water stress-related damage at a relative water content of 62 percent, where as Brutia pine chloroplasts were disrupted. It is suggested that future investigations examine the physiological manifestation of drought mechanism at the cellular and molecular levels of both species.

LD2668 .T4 1942 M42 / Master of Science

Master of Science / Department of Agronomy / Kraig L. Roozeboom / Due to decreased availability of irrigation water in central and western Kansas and an increase in water restrictions, producers are looking for more efficient ways to use available irrigation water. Drought-tolerant technologies have become popular in hybrids for stress-prone environments across central and western Kansas and are marketed for their ability to produce greater grain yields with less water. The objective of this research was to understand how DT and non-DT corn hybrids respond in a wide range of environmental conditions in terms of soil water status change, canopy indicators of stress, dry matter partitioning, and grain yield. Soil water status change, yield, and canopy response characteristics of two DT hybrids, and one non-DT hybrid were compared at five locations over two years in rain-fed, semi-irrigated, or fully irrigated regimes making a total of 18 environments. Field experiments were established in 2014 and 2015 near Topeka, Scandia, Hutchinson, Garden City, and Tribune, KS. Two corn hybrids with different approaches drought tolerance (Pioneer 1151 AQUAmax, bred drought tolerance and Croplan 6000 DroughtGard, bred drought tolerance plus transgenic drought tolerance), and one hybrid with no specific drought tolerance characteristics but with proven performance in favorable environments (Croplan 6274) were used in the experiment. Soil moisture content (measured using a neutron moisture meter), canopy temperature, ear leaf temperature, and chlorophyll content were measured at tasseling (VT), milk or dough (R3-R4), and physiological maturity (R6) developmental stages. Grain yield was at all 18 environments, and biomass production was estimated at 14 of the environments. Hybrid plasticity of yield results show the response for Croplan 6000DG and Pioneer 1151AM differed, but Croplan 6274 was the same as both other hybrids at the 0.10 alpha level. Yields of all hybrids remained comparable in most environments, but as environment yields increased beyond 200 bu acˉ¹, Croplan 6000DG lagged behind Pioneer 1151AM. Hybrid harvest index plasticity shoed that all hybrids had the same response to environment in harvest index. Although, not statistically significant, when an environment supported favorable harvest index values greater than 0.40, it’s observed that Croplan 6000DG does have an improvement in harvest index relative to the Pioneer 1151AM and Croplan 6274.

Digitized by Kansas Correctional Industries

Bibliography: leaves 134-145. The improvement of drought tolerance of commercial soybean varieties via indirect selection for transpiration efficiency (TE) in breeding programs was investigated. The extent and nature of variation for TE among soybean genotypes were established through glasshouse experiments under well watered conditions, and confirmed in the field under contrasting water stress conditions. The results suggest that increasing TE will be a beneficial strategy to improve soybean grain yield at the crop level, and a protocol developed suited to indirect selection for high TE soybean genotypes under a range of environments. This will have immediate application in the development of soybean varieties specifically adapted to the dryland production areas of the Australian sub-tropics.

No description available.

LD2668 .T4 1954 S25 / Master of Science

Call number: LD2668 .T4 1966 S761 / Master of Science

No description available.