<p>Tall waterhemp management in agronomic crops continues to be an increasing problem due to widespread resistance to herbicides, including protoporphyrinogen oxidase (PPO)-inhibitors. With limited effective postemergence herbicides, especially in soybeans, research to further understand the selection of PPO-resistant (PPO-R) tall waterhemp and identification of new herbicide resistance mechanisms is crucial for improving weed management decisions in order to slow selection for herbicide resistance and prolong the effectiveness of PPO-inhibiting herbicides.</p> <p> Previous research has shown that soil-applied applications of PPO-inhibiting herbicides can increase the frequency of the PPO resistance trait (∆G210) in surviving tall waterhemp plants, even when applied in combination at the same ratio with the very long chain fatty acid inhibitor (VLCFA), <i>s-</i>metolachlor. Field experiments were conducted to determine if selection for tall waterhemp resistant individuals to PPO-inhibitors could be reduced when the soil residual activity of <i>s</i>-metolachlor persisted longer than the PPO-inhibitor herbicide. The frequency of ∆G210 in surviving individual plants increased as the fomesafen rate increased, but was independent of the rate of <i>s</i>-metolachlor. Additionally, heterozygosity of ∆G210 in surviving individuals did not change with any rate or combination of fomesafen and <i>s</i>-metolachlor. However, saflufenacil, standard PPO-inhibitor with relatively short soil residual activity, applied alone increased the number of homozygous PPO-R tall waterhemp by 15% compared to the high rate of <i>s</i>-metolachlor and the combination of saflufenacil and <i>s</i>-metolachlor. Furthermore, this research demonstrated that end of season control of tall waterhemp plays a more vital role in delaying a large-scale shift towards herbicide resistance through reduced seed production. This can be achieved through the combination of multiple effective herbicide sites of action, including soil residual PPO-inhibitors. Tall waterhemp control and density were greatest with the high rates of fomesafen plus <i>s</i>-metolachlor, which resulted in the lowest number of PPO-R tall waterhemp that survived herbicide treatment at the end of season.</p> <p> Prior to the research conducted in this thesis, the only known resistance mechanism to PPO-inhibiting herbicides in tall waterhemp has been the ∆G210 target site mutation. A previously developed TaqMan assay used to determine the presence or absence of the ∆G210 mutation has allowed accurate, high throughput screening of this mutation. However, suspected PPO-R tall waterhemp do not always receive positive confirmation indicating the presence of an alternative resistance mechanism. Identification of additional resistance mechanisms can provide valuable insight in regards to resistance to PPO-inhibiting herbicides as well as cross resistance to other herbicide modes of action, which can lead to improved tall waterhemp management decisions. Of 148 tall waterhemp populations collected across the Midwestern U.S., 84% of the populations sampled contained at least one PPO-R biotype with the ∆G210 mutation, although several individual plants across the Midwest U.S. exhibited phenotypic resistance to fomesafen that could not be explained by ∆G210. The percentage of PPO-R tall waterhemp without ∆G210 was 19, 5, 2, 1, and 2% for Iowa, Illinois, Indiana, Minnesota, and Missouri, respectively. Following the initial greenhouse screening, subsequent tall waterhemp populations were selected that exhibited low-, mid-, and high-level resistance to fomesafen that resulted in resistance ratios from 0.6 to 17X in response to fomesafen. This research documents the variability in fomesafen response to multiple tall waterhemp populations in addition to revealing the presence of additional resistance mechanism(s), other than the previously known ∆G210 mutation that has been the benchmark for resistance to PPO-inhibiting herbicides in tall waterhemp.</p> <p> Lastly, greenhouse and lab experiments were conducted to investigate the role of antioxidant enzymes with PPO-R tall waterhemp via ∆G210. The objectives of this research were to determine if the variability in resistance ratios for PPO-R tall waterhemp documented in greenhouse and field scenarios could be due to an enhanced antioxidant enzyme pathway. Basal levels of antioxidant enzymes in PPO-S populations were not different from PPO-R populations when pooled together by respective phenotype. However, enzyme activity of tall waterhemp populations varied at the individual level, but independent of the ∆G210 mutation. This indicates that an inherent enhanced antioxidant enzyme pathway does not cause the variability in fomesafen response in tall waterhemp. With the exception of glutathione reductase, antioxidant enzyme activity following fomesafen application was generally the same for PPO-R and PPO-S populations by increasing, decreasing, or remaining unchanged. Glutathione reductase activity in PPO-S populations decreased compared to PPO-R populations from 9 to 36 HAT. By 36 HAT, all antioxidant enzyme activity for PPO-S populations was lower compared to PPO-R populations most likely a consequence of more lipid peroxidation. This research shows that antioxidant enzyme activity correlated with fomesafen application and documents the variability observed within tall waterhemp populations with and without the ∆G210 mutation. </p>

Sustainable animal production on pasture planted on rehabilitated mine land will only be possible if the optimal stocking rate for animal and pasture production is determined. A grazing trial was conducted on tall fescue, established on rehabilitated mine land and irrigated with mine waste water. The aims of this study were to quantify: a) animal performance and nutritive value at different levels of nitrogen (N) fertilization during pasture establishment, and b) intake, animal performance (defined as average daily gain; ADG) and nutritive value when different stocking rates were applied. This study was done during two seasons: season one in winter (6 June -16 July 2008) and season two in spring (28 Aug – 6 Nov 2008). In terms of post mining land use this study supplied valuable information on potential livestock production. The higher level of N fertilization applied during the winter of 2007 at pasture establishment resulted in a significantly (P < 0.05) higher crude protein (CP) concentration a year later compared to the lower levels of N fertilization. During the winter grazing season the pasture contained an average of 83.4 g CP kg-1 dry matter (DM), 601.9 g NDF kg-1 DM, 6.2 g Ca kg-1 DM and 1.7 g P kg-1 DM, the average in vitro organic matter digestibility (IVOMD) was 642.2 g kg-1 OM and the average leaf: stem ratio was 88:12. The ADG of crossbred weaner calves grazing the low N fertilization (LN), low stocking rate (LS) paddock (229.1 g day-1) was significantly (P < 0.05) lower than the ADG of weaner calves grazing the LN, high stocking rate (HS) and the high N (HN), LS respectively. The ADG of the animals in the HN, LS paddock was 482.7 g day-1 and in the LN, HS paddock was 310.6 g day-1. The low ADG for the LS treatment was due to the low CP concentration of this paddock, with values as low as 55.1 g CP kg-1 DM recorded during the winter grazing period. Low pasture nutritive value during winter can potentially limit animal production.spring grazing season the pasture contained an average of 101.0 g CP kg-1 DM, 639.1 g NDF kg-1 DM, 8.9 g Ca kg-1 DM and 2.1 g P kg-1 DM. The average leaf: stem ratio was 85:15, IVOMD was 717.5 g kg-1 OM and effective DM degradability (in situ) was 56.1 %. The average OM digestibility estimated with the alkane method varied between 720.8 to 768.3 g kg-1 depending on the alkane used and weather a correction was made for the faecal recovery of the alkane used. On average the forage available in the paddock with the LS had a significantly (P < 0.05) higher CP concentration, leaf: stem ratio and IVOMD, with a significantly (P < 0.05) lower NDF concentration than the HS paddock. This is probably due to the fact that in the HS paddock forage with a high nutritive value was removed at a higher rate. Irrespective of the calculation used, digestibility calculated by the alkane method did not differ significantly (P > 0.05) between paddocks at any time period. The average intake in the paddock with medium grazing stocking rate (MS) was significantly (P < 0.05) higher than the average for the other paddocks. The paddock with the MS was managed to supply a pasture DM allowance of 2.5 % body weight (BW). The DM intake over the spring season was 2.2 % BW. The MS treatment supplied sufficient plant material without resulting in large accumulation of plant material. The ADG for the spring season was 110.5 g day-1 and averages for each paddock did not differ significantly (P > 0.05) from each other. During the / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / unrestricted

Poisonous plants are one of the most important causes of economic losses in the livestock industry throughout the world, especially in those areas where rangeland and pasture grazing are practiced. In the livestock industry in South Africa, total annual costs of plant and fungal poisoning (mycotoxicosis) are conservatively estimated to be R104 506 077, 8% of which is due to D. cymosum poisoning. There is no antidote for D. cymosum poisoning of livestock and wide scale eradication by conventional control methods are labour intensive, expensive and often impractical. In South Africa, the communal or emerging farming sectors are the most affected. This is mainly due to the high costs associated with control measures such as fencing, supplementary feeding and veterinary expenses, and / or lack of grazing management with livestock numbers exceeding the biological carrying capacity of the rangeland due to lack of grazing lands. Proper rangeland management is the surest and most economical means of reducing plant poisoning of livestock. Focused research on the ecology of these poisonous plants in rangeland communities to improve rangeland management would assist in the development of these strategies. This study investigated D. cymosum infested savanna communities, focusing on understanding how negative (inter- and intraspecific competition) interactions influence community structure, dynamics and productivity and how plants in D. cymosum communities avoid these negative interactions by investigating their seasonal phenological patterns. Dichapetalum cymosum coexists with trees, such as Burkea africana, Ochna pulchra and Terminalia serecia, as well as shrubs species, such as Pygmaeothamnus zeyheri and Perinari capensis, in well drained, nutrient poor soils. Some plant ecologists contend that in an environment where water is limited, competition is inevitable amongst plants occupying the same above-ground stratum and the same soil horizon. Others contend that plants avoid competition with each other by sharing resources spatially and temporarily. Field experiments were conducted to investigate how the above species interact and coexist with each other in two South African savanna communities. Fourteen (100 m x 100 m) D. cymosum infested sites were identified in each community. Disperal analysis using nearest neighbour distance was used to investigate competition among species, and above ground flowering phenology along niche axes to determine temporal and spatial sharing of resources. The dispersal analysis revealed aggregated populations among species when intraspecific and combined (all individuals independent of species) analyses were conducted. However, in all instances, aggregation among species was not significant. No interspecific competition was observed among species when correlation analysis was performed between nearest neighbour distance and combined canopy cover of the nearest neighbour pair. Intraspecific competition was, however, observed for tree species T. sericea (n = 128; r = 0.3952; P < 0.0001) and B. africana (n = 166; r = 0.49926; P <0.0001) and a shrub species, D. cymosum (n = 391; r = 0.39788; P <0.0001). Segregation was found between O. pulchra and both B. africana (S = 0.999, χ² = 102.7588, P <0.0001) and T. sericea (S = 0.999, χ² = 57.8571, P <0.0001). Shrub species were also segregated, all with interspecific nearest neighbour pairs occurring less often than expected. The vegetative phenology of all experimental plant species followed the rainfall gradient. Differences in reproductive phenologies were observed between O. pulchra and both B. africana and T. sericea. Dichapetalum cymosum also differed from P. capensis and P. zeyheri in their reproductive phenologies. The differences in the reproductive strategies of at least one of the species in each growth form account for the observed spatial distribution amongst species in these communities. The observed growth patterns shown by the vegetative phenologies, however, suggest that lengthy retention of nutrients is a strategy to avoid competition for nutrient uptake with other species in these communities. Segregation between species and positive correlation iii between nearest neighbour distance and combined canopy cover of the nearest neighbour pairs suggest that intraspecific competition and interspecific facilitation determine D. cymosum woody plant community structure. This study had limited application to rangeland management. However, it can be concluded that grazing of D. cymosum communities should take place during mid-summer, when enough grazing material is available to allow animals to vary their diet. The introduction of animals in poor condition or naïve animals into these lands should be avoided in winter and spring as they will graze non-selectively resulting in D. cymosum poisoning. To utilize these areas as grazing lands, supplements need to be provided to assist in the detoxifications of toxins once ingested. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Plant Production and Soil Science / unrestricted

<p>In insect pest management, the plant volatiles and pheromones associated with host-plant location can be used to manipulate insect pest behavior by attracting or “pulling” insects from a valuable resource. Conversely, deterrents can be used to prevent behaviors or “push” insects away from a resource. If combined, attractants and deterrents can have powerful synergistic effects that promote greater response than the individual components. This dissertation explores the use of attractants and deterrents of the specialist herbivore and challenging agricultural pest, the striped cucumber beetle, <em>Acalymma vittatum</em>, to ultimately develop a push-pull management system. </p> <p><br></p> <p>In first chapter, we examine the combination of two striped cucumber beetle attractants in attract-and-kill mass trapping: live striped cucumber beetles as a proxy for aggregation pheromone, and cucurbit floral volatiles. In the second chapter, we examine natural products—essential oils, pawpaw extract, squash bugs, and kaolin clay—as a means for repelling or deterring beetles from cucurbit crops. Lastly, we combine the findings of previous chapters as way of using both attractive and deterrents to further modify striped cucumber beetle behavior and to observe potential synergies in removing these pests from cucurbit crops. In this, we use the aggregation pheromone and floral lures in attract-and-kill trapping with the deterrent kaolin. </p> <p><br></p> <p>We found that while aggregation pheromones and floral lures were useful in trapping striped cucumber beetles, floral lures may potentially distract pollinators. Striped cucumber beetle response to floral lures varied across the season and were most attractive in the late growing season, when plants were in bloom. The tested natural products did not successfully prevent beetles from colonizing plants, but instead deterred the specialist herbivore from feeding. While the attractant and deterrent did not have a synergistic effect, they remained complementary in that aggregation pheromones were useful in reducing pest populations, while kaolin clay deterred feeding. Thus, pest management systems should be flexible in timing and type of management used, and should look toward other metrics, such as feeding damage, rather than population density thresholds to measure management success. </p>

This thesis focuses on land degradation in the hinterland of Rio de Janeiro, part of the highly endangered Brazilian Atlantic Forest biome. Forest and pasture degradation are of outmost concern in the region. Thus, the main objective of this work is to provide a methodology to identify areas that fulfill the aim of increasing forest area, improving forest quality and reducing overall pasture degradation. Therefore, this work presents an approach for high-resolution land cover and pasture degradation mapping as well as an approach for prioritizing reforestation sites. Based on the prioritized land, forest scenarios are modelled and evaluated. Outcomes of this work include the recommendation to restrict land use on slopes above 10° and theoretical considerations to adapt compensatory payments for reforestation based on the priorities of the identified sites. Methods used in this work encompass image fusion using RandomForest regression, Land Cover Classification with the RandomForest classifier and Multiple Endmember Spectral Mixture Analysis (MESMA) and field methods for pasture degradation mapping.:LIST OF FIGURES XVII LIST OF TABLES XIX LIST OF ABBREVIATIONS XXI 1 INTRODUCTION 1 1.1 PROBLEM IDENTIFICATION 1 1.2 RESEARCH OBJECTIVES AND QUESTIONS 3 1.3 VALUE OF THE RESEARCH 5 1.4 STRUCTURE 6 2 CONCEPTUAL BACKGROUND 7 2.1 LAND DEGRADATION 7 2.1.1 Definition of Land Degradation 7 2.1.2 Forest Fragmentation 9 2.1.3 Pasture Degradation 14 2.2 REMOTE SENSING FUNDAMENTALS 16 2.2.1 Optical Remote Sensing 16 2.2.2 Image Classification and Land Cover Mapping 20 2.2.3 Vegetation Discrimination 22 2.2.4 Digital Elevation Model (DEM) Applications 24 2.3 LANDSCAPE METRICS 25 3 STUDY AREA 27 3.1 LOCATION 27 3.2 PHYSICAL ENVIRONMENT 28 3.3 HUMAN ENVIRONMENT 32 4 PART (A): STATE OF THE ART 39 4.1 LAND DEGRADATION IN THE GUAPI-MACACU WATERSHED 40 4.1.1 Forest Fragmentation 40 4.1.2 Pasture Degradation 42 4.2 REMOTE SENSING-BASED LAND DEGRADATION ASSESSMENTS 46 4.2.1 Forest Monitoring in the Brazilian Atlantic Forest Biome 49 4.2.2 Pasture Degradation Mapping 51 4.3 POLICIES AND PROGRAM WITH RELEVANCE TO CONSERVATION AND REFORESTATION PROJECTS IN BRAZIL 54 4.3.1 International Programs, Schemes and Intitiatives 54 4.3.2 National Environmental Policies and Programs 58 4.3.3 Policies and Programs with Focus on the Brazilian Atlantic Forest 64 4.3.4 State-based Regulations in the Rio de Janeiro Federal State 65 4.4 LAND REHABILITATION AND REFORESTATION EFFORTS IN THE RJ FEDERAL STATE 66 4.4.1 Pasture Rehabilitation 66 4.4.2 Forest Restoration 67 5 MATERIAL AND METHODS 71 5.1 GEODATA AND SOFTWARE 71 5.2 PART (B): LAND COVER AND PASTURE DEGRADATION MAPPING 73 5.2.1 Field Survey of Degraded Pastures 73 5.2.2 Satellite Data Processing 75 5.2.3 Hot Spot Analysis 86 5.2.4 Relation of Slope Angle and Degradation Class 87 5.3 PART (C): PRIORITIZATION OF REFORESTATION SITES 87 5.3.1 Preliminary Study 88 5.3.2 Spatial Multi-Criteria Evaluation (SMCE) 90 5.3.3 Forest Scenario Development and Evaluation Using Landscape Metrics 94 6 RESULTS 97 6.1 PART (B): MAPPING OF PASTURE DEGRADATION 97 6.1.1 Categorization of Pasture Degradation 97 6.1.2 High-resolution SWIR band modelling 99 6.1.3 Land Cover Classification with Random Forests 101 6.1.4 Pasture Degradation Mapping Using Spectral Mixture Analysis and Field Data 103 6.1.5 Hot Spot Analysis of Pasture Degradation 106 6.1.6 Slope Influence on Pasture Degradation 107 6.2 PART (C): PRIORITIZATION OF REFORESTATION SITES USING SMCE 109 6.2.1 Characteristics of the Prioritized Areas 109 6.2.2 Forest Scenarios 113 7 DISCUSSION 117 7.1 PART (A/B): ASSESSMENT OF THE STATUS OF LAND DEGRADATION IN THE GUAPI-MACACU WATERSHED 117 7.2 PART (B): METHODOLOGICAL APPROACH FOR PASTURE DEGRADATION MAPPING 119 7.2.1 Satellite images for high-resolution LCC 119 7.2.2 High-resolution SWIR Band Modelling 120 7.2.3 Land Cover Classification 121 7.2.4 Pasture Degradation Mapping Approach 122 7.3 PART (C): SPATIAL PRIORITIZATION FOR REFORESTATION MEASURES 125 7.3.1 Identification of Priority Sites 125 7.3.2 Forest Scenarios 127 8 CONCLUSION AND RECOMMENDATIONS 131 9 OUTLOOK 135 REFERENCES 137 ANNEX I / Die vorliegende Arbeit befasst sich mit der Landdegradation im Hinterland von Rio de Janeiro, Teil des stark gefährdeten brasilianischen Atlantikwaldbioms. Wald- und Weidedegradation zählt zu den Hauptproblemen in der Region. Das übergeordnete Ziel dieser Arbeit ist daher die Bereitstellung einer Methodik, um Flächen zu identifizieren, die zur Vergrößerung der Waldfläche und Verbesserung der Waldqualität sowie gleichzeitiger Verminderung degradierter Weiden beitragen. Aus diesem Grund stellt diese Arbeit einen Ansatz für eine hochauflösende Kartierung der Landbedeckung und der Weidedegradation sowie einen Ansatz für die Priorisierung von Wiederaufforstungs-gebieten vor. Auf der Grundlage der priorisierten Flächen werden Waldszenarien modelliert und bewertet. Ergebnisse dieser Arbeit beinhalten u.a. die Empfehlung zur Einschränkung der Landnutzung auf Hängen über 10° und theoretische Überlegungen zur Anpassung der Ausgleichszahlungen für die Wiederaufforstung auf der Grundlage der Prioritäten der Standorte. Die in dieser Arbeit verwendeten Methoden umfassen Bildfusion mittels RandomForests Regression, die hochauflösende Ableitung der Landbedeckung unter Verwendung des RandomForests Klassifiizierers, sowie spektrale Entmischung mittels Multiple Endmember Spectral Mixture Analysis (MESMA) und Feldmethoden für die Kartierung des Weidezustands.:LIST OF FIGURES XVII LIST OF TABLES XIX LIST OF ABBREVIATIONS XXI 1 INTRODUCTION 1 1.1 PROBLEM IDENTIFICATION 1 1.2 RESEARCH OBJECTIVES AND QUESTIONS 3 1.3 VALUE OF THE RESEARCH 5 1.4 STRUCTURE 6 2 CONCEPTUAL BACKGROUND 7 2.1 LAND DEGRADATION 7 2.1.1 Definition of Land Degradation 7 2.1.2 Forest Fragmentation 9 2.1.3 Pasture Degradation 14 2.2 REMOTE SENSING FUNDAMENTALS 16 2.2.1 Optical Remote Sensing 16 2.2.2 Image Classification and Land Cover Mapping 20 2.2.3 Vegetation Discrimination 22 2.2.4 Digital Elevation Model (DEM) Applications 24 2.3 LANDSCAPE METRICS 25 3 STUDY AREA 27 3.1 LOCATION 27 3.2 PHYSICAL ENVIRONMENT 28 3.3 HUMAN ENVIRONMENT 32 4 PART (A): STATE OF THE ART 39 4.1 LAND DEGRADATION IN THE GUAPI-MACACU WATERSHED 40 4.1.1 Forest Fragmentation 40 4.1.2 Pasture Degradation 42 4.2 REMOTE SENSING-BASED LAND DEGRADATION ASSESSMENTS 46 4.2.1 Forest Monitoring in the Brazilian Atlantic Forest Biome 49 4.2.2 Pasture Degradation Mapping 51 4.3 POLICIES AND PROGRAM WITH RELEVANCE TO CONSERVATION AND REFORESTATION PROJECTS IN BRAZIL 54 4.3.1 International Programs, Schemes and Intitiatives 54 4.3.2 National Environmental Policies and Programs 58 4.3.3 Policies and Programs with Focus on the Brazilian Atlantic Forest 64 4.3.4 State-based Regulations in the Rio de Janeiro Federal State 65 4.4 LAND REHABILITATION AND REFORESTATION EFFORTS IN THE RJ FEDERAL STATE 66 4.4.1 Pasture Rehabilitation 66 4.4.2 Forest Restoration 67 5 MATERIAL AND METHODS 71 5.1 GEODATA AND SOFTWARE 71 5.2 PART (B): LAND COVER AND PASTURE DEGRADATION MAPPING 73 5.2.1 Field Survey of Degraded Pastures 73 5.2.2 Satellite Data Processing 75 5.2.3 Hot Spot Analysis 86 5.2.4 Relation of Slope Angle and Degradation Class 87 5.3 PART (C): PRIORITIZATION OF REFORESTATION SITES 87 5.3.1 Preliminary Study 88 5.3.2 Spatial Multi-Criteria Evaluation (SMCE) 90 5.3.3 Forest Scenario Development and Evaluation Using Landscape Metrics 94 6 RESULTS 97 6.1 PART (B): MAPPING OF PASTURE DEGRADATION 97 6.1.1 Categorization of Pasture Degradation 97 6.1.2 High-resolution SWIR band modelling 99 6.1.3 Land Cover Classification with Random Forests 101 6.1.4 Pasture Degradation Mapping Using Spectral Mixture Analysis and Field Data 103 6.1.5 Hot Spot Analysis of Pasture Degradation 106 6.1.6 Slope Influence on Pasture Degradation 107 6.2 PART (C): PRIORITIZATION OF REFORESTATION SITES USING SMCE 109 6.2.1 Characteristics of the Prioritized Areas 109 6.2.2 Forest Scenarios 113 7 DISCUSSION 117 7.1 PART (A/B): ASSESSMENT OF THE STATUS OF LAND DEGRADATION IN THE GUAPI-MACACU WATERSHED 117 7.2 PART (B): METHODOLOGICAL APPROACH FOR PASTURE DEGRADATION MAPPING 119 7.2.1 Satellite images for high-resolution LCC 119 7.2.2 High-resolution SWIR Band Modelling 120 7.2.3 Land Cover Classification 121 7.2.4 Pasture Degradation Mapping Approach 122 7.3 PART (C): SPATIAL PRIORITIZATION FOR REFORESTATION MEASURES 125 7.3.1 Identification of Priority Sites 125 7.3.2 Forest Scenarios 127 8 CONCLUSION AND RECOMMENDATIONS 131 9 OUTLOOK 135 REFERENCES 137 ANNEX I

<p>Herbicide resistance poses a threat to sustainable vegetation management. Recently, the first report of 2,4-D resistance in buckhorn plantain (<i>Plantago lanceolata</i> L.) as well as the first report of 2,4-D resistance in turf was published. Additional 2,4-D resistant buckhorn plantain ecotypes have been reported in Indiana, Ohio, Pennsylvania, Georgia, and Virginia in the short time since. Thus, the aims of this research were to investigate the mechanism(s) of 2,4-D resistance in a resistant ecotype of buckhorn plantain, screen other potentially resistant ecotypes and measure them for fitness penalties, and identify effective turfgrass cultural control practices for managing buckhorn plantain. </p><p><br></p><p>A radiolabeled 2,4-D experiment was conducted to investigate absorption and translocation, and a 2,4-D dose-response experiment was conducted using malathion as a cytochrome P450 inhibitor to assess the potential mechanism of 2,4-D resistance in buckhorn plantain. The clearest difference between the resistant (IN-GW) and susceptible ecotype (IN-WL) was the interaction between ecotype and harvest period for [¹⁴C]2,4-D in the non-treated shoots. After 192 hr, the susceptible ecotype had a higher amount of [¹⁴C]2,4-D in the non-treated shoots (16.1%) than the resistant ecotype at any of the harvest periods (5.5-7.3%); the amount of [¹⁴C]2,4-D in the non-treated shoots was similar across all three harvest periods for the resistant ecotype. Thus, reduced translocation plays an apparent role in 2,4-D resistance in buckhorn plantain. Malathion pre-treatment did not fully revert the resistant ecotype back to susceptible. Thus, if cytochrome P450 metabolism is part of the 2,4-D resistance mechanism of this buckhorn plantain ecotype, it is likely a contributor and not the sole mechanism of resistance. </p><p><br></p><p>In total, this research identified four 2,4-D resistant buckhorn plantain ecotypes from Indiana and one from Ohio. Only one report of a failure to control buckhorn plantain was confirmed to be a susceptible ecotype. When compared to susceptible ecotypes in a garden study, no major fitness penalties were identified in resistant ecotypes. </p><p><br></p><p>Given that no specific cultural or biological control methods of buckhorn plantain have been recognized to date, two field trials were conducted to investigate the influence of 1) mowing height and nitrogen rate on buckhorn plantain coverage and 2) mowing frequency on buckhorn plantain coverage and seed production. Nitrogen fertilization and low mowing reduced buckhorn plantain coverage after 3 yr, but low mowing also increased crabgrass and dandelion as well as reduced turf quality. Frequent mowing reduced viable seed production, but that did not translate into a reduction in buckhorn plantain coverage after 2 yr. </p><p><br></p><p>This research demonstrates the complex mechanism of action of 2,4-D, as the resistance mechanism for buckhorn plantain was not fully elucidated. It also highlights the importance of utilizing best management practices for managing weeds in turf, including rotating herbicide chemistries, high and frequent mowing, and nitrogen fertilization.</p>

<p>  </p> <p>Modern agriculture must address the massive challenge of providing food for the increasing population. The challenge lies in increasing crop yield and reducing losses caused by abiotic and biotic stresses. In fact, for some crops, such as wheat and maize, over 40% of the production is lost due to environmental conditions (abiotic stresses) or pests and pathogens (biotic stresses). Specialists in the area are suggesting a need for a second green revolution to meet the increasing demand in food production. While in the first green revolution was focused on breeding and genetics to produce crops' genetic lines with a higher yield. The second green revolution will utilize cutting-edge technologies to increase yield and reduce crop losses. The development of remote sensing technologies and their applications is the main driving force of modern agricultural practices. Currently, farmers are relying more on automation, data collection, and data analysis to manage farming operations. The reliance on remote sensor technologies is a game-changer for traditional agricultural practices, and it is contributing tremendously to increasing production and avoiding yield losses. Hyperspectral phenotyping is an emerging remote sensing technology that utilizes the light's reflectance to provide insightful information about plant traits. For several years, research groups have been applying hyperspectral phenotyping techniques to detect plant traits information, such as nitrogen content, photosynthesis rates, pests infestation, and abiotic stress detection. Although this is not a novel approach to plant traits detection, this technology application is not mature yet. Several challenges are associated with using hyperspectral information for phenotyping, such as model transferability, data collection scalability, and the heritability of plant traits retrieved using hyperspectral data. In my thesis dissertation, I addressed some of those challenges contributing to advances in hyperspectral phenotyping. My results demonstrate that using full-range hyperspectral reflectance data (400-2400nm) to retrieve nitrogen in winter wheat increases the model transferability across years and genotypes. Predicting nitrogen content using hyperspectral data can be used as a surrogate to calculate nitrogen use efficiency traits. My research highlights the hurdles associated with spectral detection of stresses interaction, such as drought stress, which can mask western corn rootworm detection in maize. Finally, I explored the correlation among spectral, functional, and field traits in a soybean NAM (Nested Association Mapping) population to understand the relationship among those traits' variability and how that information can be used for soybean breeding programs. The outcomes of my thesis dissertation advance the knowledge in the hyperspectral phenotyping field and its application to modern agriculture. Consequently, my study also contributes to food security programs by providing insightful information about the hyperspectral assessment of plant health status, which is essential to increase yield production and reduce crop losses. </p>

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. Johannesburg 1990. / No abstract provided.

Summer pasture-associated recurrent airway obstruction (SPARAO) is characterized by reversible airway obstruction resulting from airway hyper-reactivity to aeroallergens, mucus accumulation, and airway inflammation. These are key clinical features that are shared with human asthma, suggesting SPARAO’s utility as an animal asthma model. SPARAO affects horses maintained on pasture in conditions of high heat and humidity. Common in the southeastern United States, the cause of SPARAO is unknown, but is presumed to reflect reactivity to seasonally inhaled pasture-associated aeroallergens. This investigation sought to identify well-characterized histopathological lesions of human asthma, collectively termed ‘asthmatic remodeling’, in lung tissue from horses with SPARAO. Two histological staining techniques were used: H&E and Movat’s Pentachrome. Similar to chronic asthma, lung tissue from horses with SPARAO demonstrates statistically significant increases in airway smooth muscle, fibrosis, airway occlusion and inflammation, goblet cell hyperplasia, and remodeling of terminal bronchioles and elastin fibers.

<p>Phytophthora root and stem rot (PRSR), caused by oomycete <i>Phytophthora sojae</i>, is the most severe soil-borne disease of soybean (<i>Glycine max</i> (L.) Merr.) worldwide. The disease can be effectively managed by introducing resistance to <i>P. sojae</i> (<i>Rps</i>) genes into soybean cultivars by breeding, which requires continuous efforts on identification of resistance resources from soybean germplasm. Previously, two resistance genes, <i>Rps2-cas</i> (former name <i>Rps2-das</i>) and <i>Rps14 </i>(former name<i> Rps1-f</i>), were mapped by linkage analysis from soybean landraces, PI 594549 C and PI 340029, respectively. The resistance underlying PI 594592 also need further characterization given its broad resistance spectrum. In this study, <i>Rps-2cas</i> and <i>Rps14</i> were further mapped, and <i>Rps2-b</i>, was identified and initial mapped from PI 594592. Thus, this thesis research was divided into three parts for three <i>Rps</i> genes.</p><p>The first part mainly focuses advances on <i>Rps2-cas</i>. Marker-assisted spectrum analysis was performed for <i>Rps-2cas</i> to confirm its potential in disease management. A high-quality genome assembly of PI 594549 C was generated, and KASP markers were developed based on comparison between new reference and Williams 82 reference genome. The gene was further mapped to a 32.67-kb region on PI 594549 C reference genome harboring three expressed NLRs by 24 recombinants screened from a large F₄ population. Comparative genomics analysis suggests the only intact NBS-LRR gene in the fine mapping region is the best candidate gene for <i>Rps2cas</i>, and its function was validated by stable transformation. Evidences from other high-quality assembly genomes suggest <i>Rps2-cas</i> originated from an ancient unequal crossing over event.</p> <p>In the second part, <i>Rps14</i> was further mapped using 21 recombinants identified from a F₃population consisting of 473 plants. In commonly used Williams 82 reference genome, the assembly of fine mapping region was incomplete, and <i>Rps14</i> region showed drastic variation in size and copy number of NLRs in 23 high-quality genome assemblies, suggesting the complexity of <i>Rps14</i> region and high-quality reference sequence of donor line is required for isolation of <i>Rps14</i> candidate genes. Marker assisted resistance test showed <i>Rps14</i> had wider resistance spectrum to different <i>P. sojae </i>isolates comparing to other <i>Rps</i> genes on chromosome 3, and phylogenic analysis further supported the potential of <i>Rps14</i> to be a novel resistance gene. </p> <p>For the third part, an F₂population derived from a cross between PI 594592 and Williams was tested by <i>P. sojae</i> race 1. The 3:1 and 1:2:1 Mendelian segregation ratios were observed in F₂individuals and F_2:3families, respectively, suggesting a single dominant <i>Rps</i> gene in PI 594592. The gene was initially mapped to the distal end chromosome 16 overlapped with <i>Rps2</i>, and the gene was tentatively named as <i>Rps2-b</i>. Polymorphic SSR markers and InDel markers designed based on re-sequencing data of PI 594592 and Williams was used to genotyping all the F_2:3families, and a linkage map was constructed for <i>Rps2-b</i>. <i>Rps2-b</i> was mapped to a 461.8-kb region flanked by SSR marker Satt431 and InDel marker InDel3668 according to the reference genome (Wm82. a2). Marker-assisted resistance test showed <i>Rps2-b</i> hold a wide resistance spectrum. </p>