Plant Pathology Commons^™

Understanding How The Effectors Hopd1 And Hopg1 From The Bacterial Pathogen Pseudomonas Syringae Pv. Tomato Dc3000 Target The Arabidopsis Thaliana Protein Atnhr2b To Cause Disease In Plants, Catalina Maria Rodriguez Puerto

Graduate Theses and Dissertations

The pathogenicity of Pseudomonas syringae is associated with the type III secretion system (T3SS), a complex of proteins assembled in the inner and outer bacterial membranes that traverses the plant cell wall to deliver bacterial proteins into the cytoplasm of plant cells. The effector proteins translocated into the plant cells are called Hops (Hypersensitive response and pathogenicity outer proteins). Bacterial effectors target plant immune proteins to suppress defense responses and enhance bacterial parasitism. The Arabidopsis thaliana nonhost resistance 2B (AtNHR2B), a recently identified immune protein, is degraded after inoculation with the adapted pathogen of Arabidopsis, P. syringae pv tomato DC3000 …

Mitigating Herbicide Impacts To Soybean, Grant Lawson Priess

Graduate Theses and Dissertations

The rapidity in evolution of herbicide-resistant weeds and the resulting cost to U.S. farmers demonstrate the need to responsibly steward the limited number of herbicides available in agricultural systems. To reduce weed emergence and likewise added selection pressures placed on herbicides, early-season crop canopy formation has been promoted. However, impacts to soybean following a potentially injurious herbicide application have not been thoroughly evaluated. Therefore, field experiments were conducted to determine whether: 1) soybean injury from metribuzin or flumioxazin delayed canopy formation or changed the incidence of pathogen colonization; 2) residual herbicides applied preplant reduced the potential for soybean injury and …

Phenotypic Study Of Anthracnose Resistance In Black Walnut And Building A Mapping Population, Sadie D. Land

Graduate Theses/Dissertations

Black walnut anthracnose, caused by Gnomonia leptostyla, is the most widespread and destructive disease affecting black walnut trees (Juglans nigra). Breeding cultivars for a higher resistance to anthracnose is a natural and efficient strategy for improving the health and production quality of black walnut trees. The two goals of this study were to reveal that the ‘Sparrow’ cultivar of black walnut contains a significantly higher resistance to anthracnose than the ‘Football’ cultivar when separated from environmental factors, and to expand the ‘Football’ × ‘Sparrow’ F1 mapping population to evaluate how the trait of resistance is inherited in the progeny. A …

Methods To Evaluate Ruminant Animal Production Responses, Jose Manuel Diaz Gomez

Graduate Theses and Dissertations

In experiment 1, 80 steers (197.0 kg initial body weight; BW for fall, 116.9 kg for spring), were stocked at 2.45 and 4.1 calves/ha in fall and spring, respectively in 16 tall fescue pastures [fall ergovaline (EV) = 1,475 ppb and spring EV = 1,173 ppb] under 2 treatments, mineral (MIN) (n = 8) and cumulative management (CM) (n = 8). Forage allowance did not differ (P = 0.76) between CM and MIN during fall but differed during spring (P ≤ 0.05, 2.55 vs. 3.22 kg DM/kg BW, for MIN and CM, respectively). For fall, average daily gain (ADG) resulted …

Evaluation Of Pheromone Mating Disruption For California Red Scale Control In Commercial California Citrus, Joel Timothy Leonard

Master's Theses

California red scale (CRS), Aonidella aurantii, is an increasingly injurious insect pest for the California citrus industry due to insecticide resistance, changing weather patterns, and shifting trade regulations. The presence of the insect on fruit, damages the rind of the fruit and high populations can cause dieback of branches as well as lower yields. Pheromone mating disruption of CRS has the potential to alleviate population control concerns and reduce insecticide use. The efficacy of the pheromone mating disruption technique for pest management of CRS was determined using the products CheckMate® CRS and Semios CRS Plus. CheckMate® CRS was evaluated …

Genetic Resistance To The Downy Mildew Pathogen And Mapping The Rpf Resistance Loci In Spinach, Gehendra Bhattarai

Graduate Theses and Dissertations

Spinach (Spinacia oleracea) is an important cool-season leafy vegetable crop in the United States (US). Downy mildew, caused by the obligate oomycete Peronospora effusa, is the most economically important disease of spinach. A total of 17 races of P. effusa have been reported on spinach, and many of these races (>10) have emerged in the last three decades. The new races of the pathogen are continually overcoming the genetic resistances used in the newly released cultivars.

A detached leaf inoculation assay was evaluated, standardized, and validated as a new method to differentiate resistant and susceptible spinach genotypes. Disease response …

Nematode Populations As Affected By Residue And Water Management In A Long-Term Wheat-Soybean Double Crop In Eastern Arkansas, Lucia Emperatriz Escalante Ortiz

Graduate Theses and Dissertations

Soybeans (Glycine max) are one of the major row crops in the United States, particularly in Arkansas. Soybean cyst nematode (SCN, Heterodera glycines) and southern root-knot nematode (RKN, Meloidogyne incognita) are two of the most damaging pests that cause major economic losses in soybeans. Little is known concerning the effects of common and alternative agronomic practices on nematodes in fields with nematode population densities below threshold levels. Therefore, the objective of this study was to evaluate the effects of the combination of tillage (conventional tillage and no-tillage), irrigation (irrigated and non-irrigated), wheat (Triticum aestivum) residue burning (burned and no burned), …

Evaluation Of Topramezone For Use In Rice (Oryza Sativa L.) Production, Matthew Moore

Graduate Theses and Dissertations

The rapid development of resistant weeds, particularly to postemergence-applied herbicides, is a growing concern to rice producers worldwide. Barnyardgrass, one of the most problematic weeds in rice cropping systems, alone has been found to be resistant to four herbicide sites of action (SOA) in certain populations, leaving growers no options for control. This unsettling fact has led to research on other SOAs that have not previously been used in US rice. One SOA that has garnered interest is the 4-hydroxyphenylpyruvate dioxygenase (HPPD)- inhibiting herbicides. The only HPPD-inhibitor that will soon be labeled for use in US rice is benzobicyclon. The …

Lucerne For Acid Soils: A Field Evaluation Of Early Generation Aluminium Tolerant Genotypes, Richard C. Hayes, Guangdi Li, Shoba Venkatanagappa, Alan W. Humphries, Ross Ballard

IGC Proceedings (1977-2023)

The development of lucerne germplasm tolerant of acidic soil conditions has long been a research objective of international significance. Many initiatives have previously failed to produce genotypes with adequate improvement in tolerance to be deemed economically viable and as a consequence, still no cultivar of lucerne exists that has improved adaptation to acidic soils. An Australian research program spanning the previous decade sought to redress this issue by developing lucerne genotypes with significantly enhanced tolerance to aluminium (Al) toxicity. Using recurrent selection in hydroponic solution culture, populations selected comprised individuals which displayed enhanced seedling root growth following a pulse of …

Dissecting Drought-Response Strategies Of Perennial Ryegrass (Lolium Perenne L.), Jean-Hugues B. Hatier, Lulu He, Marty J. Faville, Micheal J. Hickey, Chris S. Jones, Mohamed Z. Z. Jahufer, Cory Matthew

IGC Proceedings (1977-2023)

Periodic drought is a severe constraint on the profitability and sustainability of pastoral production. As a result of climate change, drought events are anticipated to increase in frequency and intensity even in regions where annual precipitation is unchanged, as well as where it is reduced.

Many studies have been carried out on drought resistance of forage species (Holloway-Phillips and Brodribb 2011). However, for most experiments, it is unclear which mechanism(s) are responsible for variation in plant performance under moisture stress, whether drought response mechanisms were triggered, or whether differences in performance were simply the result of intrinsic plant vigour. The …

The Effect Of Salinity Stress On Seed Germination Of Agropyron Elongatum, Ghasem Ali Dianati Tilaki, Arezu Alizadeh, Behnam Naserian Khiabani

IGC Proceedings (1977-2023)

Successful seedling establishment depends on the frequen-cy and the amount of precipitation as well as on the ability of the seed species to germinate and grow while soil mois-ture and osmotic potentials decrease. Germination and seedling characteristics are the most valuable criteria for selecting salt tolerance in plants. Salinity stress can reduce seed germination through osmotic effects (Jamil et al. 2006). Agropyron is a perennial grass genus with 19 dif-ferent species reported. This genus has wide adaptation and can be grown in different climates.

The objective of this study was to evaluate the impact of salinity stress on the germination …

Messina (Melilotus Siculus)–A New Pasture Legume For Saltland, Amanda L. Bonython, Andrew D. Craig, Ross A. Ballard, Nigel Charman, Philip G. H. Nichols, Clinton Revell, Natasha L. Teakle

IGC Proceedings (1977-2023)

Messina (Melilotus siculus ((Turra) Vitman ex B.D. Jacks)) is a new annual pasture legume for saltland in temperate Australia and regions of the world that experience Mediterranean climates. Messina has greater tolerance to the combined stresses of salinity and water-logging than existing commercial pasture legumes. Coupled with desirable agronomic traits these characteristics give messina the capacity to rehabilitate saltland and increase productivity on land where existing legumes fail. This paper reviews the agronomic perform-ance of messina in relation to top soil salinity levels.

Agronomic Traits In Tall Fescue Populations Under Irrigated And Rain-Fed Conditions, M. Anowarul Islam, Malay C. Saha

IGC Proceedings (1977-2023)

Grasslands and native rangelands are the predominant land-use all over the world. Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] is a cool-season perennial grass widely grown throughout the temperate regions of the world and an important component of the grasslands. Drought can have serious consequences on performance of agriculture, soil and plant health, and economics. Developing drought tolerant plants that can maintain productivity during drought, will have great environmental and economic benefits to farmers. A tall fescue population was developed by crossing a drought tolerant genotype to a susceptible genotype. The population was evaluated for different morphological and yield traits …

Mechanisms Of Stress Tolerance In Xerophyte Zygophyllum Xanthoxylum And Their Application In Genetic Improvement Of Legume Forages, Suomin Wang, Aike Bao, Qing Ma, Lijun Yue, Jinlin Zhang, Guoqiang Wu, Jiejun Xi, Yanwen Wang

IGC Proceedings (1977-2023)

Xerophytes, naturally growing in desert areas, have evolved multiple protective mechanisms to survive and grow well in harsh environments. Zygophyllum xanthoxylum, a succulent xerophyte with excellent adaptability to adverse arid environments and a fodder shrub with high palatability and nutrient value, colonizes arid areas in China and Mongolia. In this study, we found that Z. xanthoxylum grew better responding to salt condition with a typical feature for halophytes and became more tolerant to drought in the presence of moderate salinity (50 mM NaCl); 50 mM NaCl alleviated deleterious impacts of drought on the growth of Z. xanthoxylum by improving …

Advances In Improving Tolerance To Waterlogging In Brachiaria Grasses, Juan A. Cardoso, Juan Jiménez, Joisse Rincón, Edward Guevara, Rein Van Der Hoek, Andy Jarvis, Michael Peters, John Miles, Miguel Ayarza, Socorro Cajas, Alvaro Rincón, Henry Mateus, Jaime Quiceno, Wilson Barragán, Carlos Lascano, Pedro Argel, Martin Mena, Luis Hertentains, Idupulapati M. Rao

IGC Proceedings (1977-2023)

Poor drainage is found on about 11.3% of agricultural land in Latin America where physiography promotes flooding, high groundwater tables, or stagnant surface water (waterlogging). Waterlogging drastically reduces oxygen diffusion into the soil causing hypoxia which is the main limitation that reduces root aerobic respiration and the absorption of minerals and water. Under waterlogging conditions plants can adapt with traits and mechanisms that improve root aeration such as production of aerenchyma and development of adventitious roots. During the rainy season Brachiaria pastures are exposed to waterlogging conditions that can severely limit pasture productivity and hence animal production. The main objective …

Improved Drought Stress Tolerance Of White Clover Through Hybridisation With Trifolium Uniflorum L., Shirley N. Nichols, Rainer W. Hofmann, Isabelle M. Verry

IGC Proceedings (1977-2023)

The objective of this study was to determine the effect of hybridisation with Trifolium uniflorum L. on drought resistance of Trifolium repens L. (white clover). Shoot dry weight of backcross 1 (BC1) hybrids was reduced less by water stress than for backcross 2 (BC2) hybrids and white clover, as were key morphological traits such as leaf area. Under water stress, important differences for the BC1 generation compared to white clover also included lower senescence, higher stolon density, increased root dry weight, and a higher maximum nodal root diameter. Drought decreased the net photosynthetic rate by up to 48% in BC2 …

Designing Resilient And Sustainable Grasslands For A Drier Future: Adaptive Strategies, Functional Traits And Biotic Interactions, Florence Volaire, Karim Barkaoui, Mark Norton

IGC Proceedings (1977-2023)

In many regions of the world, such as Southern Europe and most Mediterranean areas, the frequency and magnitude of droughts and heat waves are expected to increase under global warming and will challenge the sustainability of both native and sown grasslands. To analyze the adaptive strategies of species, genotypes and cultivars, we aim both: (1) to understand the composition and functioning of natural grasslands; and (2) to propose ideotypes of cultivars and optimal composition for mixtures of species/genotypes under water deficit and high temperatures. This review presents a conceptual framework to analyze adaptive responses of perennial herbaceous species, starting from …

Australian Grasslands Research At The Crossroads, Alan Robson

IGC Proceedings (1977-2023)

Grasslands research in Australia is at a crossroad. There are several difficulties. First, the decline of sheep production and dairying within Australia and increased cropping has focused attention on crop research rather than pasture research. Second, enrolments in agricultural and related education have declined, and graduate numbers are insufficient to meet demand for expertise. Third, there has been a move towards specialisation in research and there are relatively few generalist agricultural scientists able to integrate research results into agricultural ecosystems. There remain very many challenges. Adapting grassland production to minimize the emission of carbon dioxide and methane is a major …

International R D & E Investment: Revitalising The Skill Base In Grassland Research And Practice, Ralph Von Kaufmann

IGC Proceedings (1977-2023)

Grasslands make up about 40.5% of the world’s land surface, and almost everywhere they make vital contributions to food supplies, livelihoods, watersheds, conservation of biodiversity and to ameliorating climate change through carbon sequestration. However, grasslands are under-represented in discussions on food security and livelihoods. Despite large investments in building human capacity, improving production systems and in research, grasslands are continuing to degrade and there is no let-up in sight for the consequent strife, famines and conflicts among the pastoral and other communities that depend on them. This review of grassland issues identified many critical skills that are lacking but it …

Drivers Of Change For Grassland And Forage Systems: A Case Study Of China, Yingjun Zhang, L. Z. Zhang, M. L. Wang, X. L. Li, Q. C. Yang, J. Hanson, M. A. Jorge

IGC Proceedings (1977-2023)

Grassland and forage systems have changed dramatically across the world. This paper describes some of the key drivers of change of grassland and forage systems using examples from China as a case study. The key drivers of change for grassland and forage systems include political, economic, social, technical and environmental factors and their impact on changes in grasslands ecosystems in China is discussed. There are interactions among the drivers and their impact is similar in many developing countries.