Life Sciences 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 …

The Effects Of Seed-Applied Fluopyram On Root Penetration And Development Of Meloidogyne Incognita On Cotton And Soybean, Tracy Hawk

Graduate Theses and Dissertations

Plant-parasitic nematodes are major pests of cotton and soybean in Arkansas, and across the Southern United States. These nematodes cause more than $3 billion worth of crop losses each year, in part due to lack of available control tactics, such as nematicides. Fluopyram has recently been registered as a seed-treatment nematicide in agronomic crops. The toxicity of fluopyram against Meloidogyne incognita infection has been reported, however, information on root protection provided by fluopyram against Meloidogyne incognita is lacking. The first objective of this research was to evaluate the effect seed-applied fluopyram had on nematode development, root galling, and reproduction on …

Use Of Aerial Imagery And Novel Experimental Design To Determine The Distribution Of Foliar Diseases On Soybean And Improve Efficiency Of Product Testing, Mckayla Patterson

Graduate Theses and Dissertations

Soybeans are grown on approximately 1.3 million ha in Arkansas generating an estimated $1.7 billion annually. Foliar diseases on soybean can result in economic losses. Growers spend significant time and money on disease scouting via crop consultants and often (subsequent) fungicide applications. Fungicide trials are often arranged in small plots designs. In these scenarios, spatial variability of foliar disease is minimized. While it is advantageous to minimize variance outside of treatment differences, another limitation with many small plot trials is ample disease pressure or having only lower severity. Within a commercial production field, soil types and disease severities vary. Logically, …

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 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 …

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 …

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), …

Arkansas Wheat Cultivar Performance Tests 2018-2019, R. E. Mason, R. G. Miller, D. E. Moon, J. P. Kelley

Arkansas Agricultural Experiment Station Research Series

Wheat cultivar performance tests are conducted each year in Ark- ansas by the University of Arkansas System Division of Agriculture’s Arkansas Agricultural Experiment Station, Department of Crop, Soil and Environmental Sciences. The tests provide information to companies developing cultivars and marketing seed within the state and aid the Arkansas Cooperative Extension Service in formulating cultivar recommendations for small-grain producers. The tests are conducted at the Northeast Research and Extension Center at Keiser, the Vegetable Substation near Kibler, the Lon Mann Cotton Research Station near Marianna, the Newport Extension Center near Newport, the Rohwer Research Station near Rohwer, the Pine Tree …

Summaries Of Arkansas Cotton Research 2018, Fred Bourland

Arkansas Agricultural Experiment Station Research Series

Arkansas ended the 2018 season ranked 5th nationally in harvested acres (480,000 acres), 4th in lint yield (1150 lb/acre), and 4th in total production (1,150,000 bales). The string of consecutive years with good yields is helping to drive the increase in cotton acres. Harvest and ginning capacity is a major limiting factor for acre expansion. Cotton planting intentions for 2019 released in late March are at 580,000 acres, up 20% from the 485,000 acres planted in 2018. This continues to push the ginning capacity of 28 gins in 2018 and on-farm picker capacity to the limit. Optimism for cotton is …

B.R. Wells Arkansas Rice Research Studies 2018, R. J. Norman, K. A.K. Moldenhauer

Arkansas Agricultural Experiment Station Research Series

No abstract provided.

Studies On Pathogenesis Of The Diseases Caused By Macrophomina Phaseolina And Phomopsis Longicolla On Soybean, Marcio Leizer Zaccaron

Graduate Theses and Dissertations

Soybean (Glycine max), a legume, is an economically important crop in many parts of the world, including the USA, Brazil, Argentina, China, and India, currently the top five producing countries. Soybean is primarily used as feed, with incising markets for food and biodiesel. Similar to most crops, soybean yield and quality are affected by a diverse group of plant pathogens. In particular, several species of filamentous fungi have been the cause of severe yield losses in most growing regions world-wide. The soil born fungus Macrophomina phaseolina, causal agent of charcoal rot, has been found to be endemic to several soybean …

Selectivity Of Infrared Heat Treatment On Inactivation Of Mycotoxigenic Fungi On Stored Grain, Shantae A. Wilson

Graduate Theses and Dissertations

Selective Infrared (IR) heating holds great potential to decontaminate spores of unsafe fungi in corn. The objectives for this study were to investigate the impact of exposing corn to infrared energy at selected peak wavelengths (λ), infrared intensities and treatment durations, followed by tempering for further inactivation of microbes on the grain and explore a method for decontaminating Aspergillus flavus (A. flavus) spores on corn. Freshly harvested corn with initial moisture contents (IMCs) of 16%, 20%, and 24% wet basis (w.b.) were used. The corn samples were treated at different infrared wavelengths (3.2, 4.5, and 5.8 μm) for 20, 40 …

The Effect Of Prescribed Burning On Wood-Decay Fungi In The Forests Of Northwest Arkansas, Nawaf Ibrahim Alshammari

Graduate Theses and Dissertations

Prescribed burning is defined as the process of the planned application of fire to a predetermined area under specific environmental conditions in order to achieve a desired outcome such as land management. This project used both morphological and molecular methods to identify and characterize the wood-decay fungi associated with the forests of northwest Arkansas—Pea Ridge National Military Park, Devil’s Den State Park, and the Buffalo National River—through frequent visits made between February 2018 and February 2019. In addition, in order to assess the effects of prescribed burning, incubation chambers were used to compare the growth of fungi from both unburned …

Investigating The Connection Between Light, A Circadian Clock, And Pathogenesis In Cercospora Zeae-Maydis, John Byron Ridenour

Graduate Theses and Dissertations

Gray leaf spot is a globally important foliar disease of maize caused by the fungus Cercospora zeae-maydis. In C. zeae-maydis, light is a critical environmental signal linked to pathogenesis and secondary metabolism. However, the mechanisms by which the fungus senses and responds to light are not fully understood. Thus, the overarching goal of this project was to unravel the connection between light and pathogenesis in C. zeae-maydis. The conserved fungal protein White Collar-1 (WC-1), designated Crp1 in C. zeae-maydis, senses light and initiates physiological responses. In fungi, WC-1 functions in the White Collar Complex via interaction with White Collar-2 (WC-2). …

Mining For Biological Control Agents Against B. Glumae, The Causal Agent Of Bacterial Panicle Blight Of Rice., Katherine Anne Wilkinson

Graduate Theses and Dissertations

Burkholderia glumae is the causal agent of the emerging disease, Bacterial Panicle Blight of rice, a serious disease that can significantly decrease yield and poses a threat to rice production worldwide. This thesis is concerned with searching for a biological control agent to control this disease. Plant associated microbes are a good source of beneficial bacteria which can be exploited for use as a biological control agent. It is possible that the microbiomes of cultivars which are known to be more resistant to plant pathogens may contain more microbes which inhibit those pathogens and therefore could be used as biological …

Factors Influencing The Spatial Distribution Of Southern Rust In Corn, Justin Bailey

Graduate Theses and Dissertations

Southern rust caused by the fungus Puccinia polysora (Underwood) is the most economically important foliar disease in corn (Zea mays) (Linnaeus) (Cyperales: Poaceae)) for Arkansas. The objective of this work was to determine distribution of southern rust in corn and to determine factors that may control its distribution.

During the 2017 and 2018 season, seven corn fields in Arkansas were rated for southern rust. After disease confirmation, fields were marked with GPS sample point locations in a grid pattern across the entire field. Ratings for disease severity were taken below, at, and above the ear leaf at each point every …

The Impact Of Fall Armyworm, Spodoptera Frugiperda (J.E. Smith), Feeding And Mechanical Defoliation On Growth And Yield Of Rice, Oryza Sativa (L.), Layton Denman Mccullars

Graduate Theses and Dissertations

The fall armyworm, Spodoptera frugiperda (J.E. Smith), (FAW) is a serious pests of many crops, and can be observed feeding throughout the entire growing season on rice, Oryza sativa, (L.). A new defoliation based threshold would help rice growers and consultants make more economically sound decisions for FAW. Work from this thesis focuses on determining the amount of damage caused by FAW feeding at different growth stages and effective insecticide seed treatments for controlling this pest.

Field plots were mechanically defoliated to determine grain yield loss across multiple growth stages and defoliation percentages. Results indicated that defoliation in late vegetative …