Fungicide selection and timing to manage southern rust of corn

Foliar corn diseases are among the most important yield-limiting factors that affect commercial corn production in the Mid-South. Southern rust is caused by the fungus Puccinia polysora, which only infects corn and is reintroduced each year from the tropic regions of Central America and the Caribbean. Symptoms consist of small orange pustules that are often first detected on leaves located in the mid- to upper-canopy. As conditions favor disease development initial infections produce spores that are spread to nearby plants and nearby fields resulting in secondary infections and the spread of southern rust

Effect of temperature and genetic structure on adaptive evolution at a dynamic range edge in the North American gypsy moth (Lymantria dispar L.)

The study of biological invasions is not only essential to regulate their vast potential for ecological and economical harm, they offer a unique opportunity to study adaptive evolution in the context of recent range expansions into novel environments. The North American invasion of the gypsy moth, Lymantria dispar L., since its introduction in 1869 to Massachusetts, has expanded westward to Minnesota, northward to Canada, and southward to North Carolina. Fluctuating range dynamics at the southern invasive edge are heavily influenced by heat exposure over their optimal (supraoptimal) during the larval stage of development. We coupled genomic sequencing with reciprocal transplant and laboratory-rearing experiments to examine the interactions of phenotypic, genetic, and environmental variation under selective supraoptimal regimes. We demonstrate that while there is no evidence to support local adaptation in the fitness-related physiological traits we measured, there are clear genomic patterns of adaptation due to differential survival in higher temperatures. Mapping of loci identified as contributing to local adaptation in a selective environment and those associated with phenotypic variation highlighted that variation in larval development time is partly driven by pleiotropic loci also affecting survival. Overall, I highlight the necessity and inferential power gained through replicating environmental conditions using both phenotypic and genome-wide analyses

Investigations of phase transitions in magnetic materials by magnetic-field- and temperature-dependent x-ray diffraction

The subject of this doctoral work is the assembly of a laboratory-based x-ray diffractometer with magnet and non-ambient sample temperature environment for investigations of magnetic materials. A special focus is on the versatility and accessibility of the instrument. The x-ray diffractometer serves as important analysis tool for the determination of the crystallographic unit cell and derived parameters like strain or expansion as function of the temperature and magnetic field. Some materials undergo structural or magnetic phase transformations under specific conditions, which can be induced within the x-ray diffractometer. These phase transformations, and their effect on crystallographic parameters of the investigated materials can be followed in situ in the instrument. Several case studies of investigations of magnetoelastic and magnetostructural phase transitions at temperatures between 25 to 600 K under various magnetic fields highlight the performance and capabilities of the instrument. The final x-ray diffractometer setup is equipped with a 5.5 T magnet and cryofurnace for non-ambient measurements in the range between 11–700 K. Measurements in transmission geometry result in reliable reflection intensities that allow for the refinement of structural parameters, and even structure solution from the diffraction data. The fast position-sensitive Si strip detector has a large angular coverage, and allows for quick data collections. High resolution data can be collected with the use of a monochromator crystal at the expense of photon flux instead of the high flux x-ray mirror optics. Integration of all diffractometer components into the control software enables the use of macros for automated data collection for a series of different measurement conditions. The first set of case studies is related to materials with a magnetoelastic phase transition, MnB, FeB and LaFe11.4Si1.6, which exhibit no structural change over the course of the magnetic ordering, but a large elastic response. Synchrotron and neutron scattering studies complement the characterization with the lab-based diffractometer with magnet, and reveal the first-order character of the phase transition. Spin fluctuations are the connecting driving force behind the magnetovolume effects and anomalies over the course of the phase transition in MnB, FeB and LaFe11.4Si1.6. The term spin fluctuations, however, describes different phenomena in the investigated materials and is clarified accordingly. The second set of case studies is related to the (La,Ce)Fe12B6 class of materials. They undergo a magnetic-field-induced phase transition at low temperatures that is coupled with a huge magnetostriction. The origin behind this anisotropic expansion over the course of the phase transition is determined as magnetic-field-induced magnetostructural phase transition into a new ferromagnetic structure. The structure is determined from the x-ray diffraction data collected in magnetic fields. A model for the transformation mechanism in the form of a martensitic-like phase transition is proposed. The model also explains the burst-like growth of ferromagnetic phase in the matrix of surrounding grain boundaries. A kinetic arrest of the ferromagnetic structure occurs, and results in a delay and large hysteresis of the magnetostructural phase transition

Efficacy of abamectin as a seed treatment for control of Meloidogyne incognita and Rotylenchulus reniformis on cotton

Abamectin is a blend of B1a and B1b avermectins that is being used as a seed treatment to control plant-parasitic nematodes on cotton. Data on the toxicity of abamectin and its effectiveness as a seed treatment to control Meloidogyne incognita or Rotylenchulus reniformis on cotton are lacking. The toxicity of abamectin was based on an assay of nematode mobility, LD50 values of 1.56 µg/ml and 32.9 µg/ml were calculated based on 2 hr exposure for M. incognita and R. reniformis, respectively. There was no recovery of either nematode after exposure for 1 hr to its LD50 concentration. Sublethal concentrations greater than 0.39 µg/ml for M. incognita and 8.2 µg/ml for R. reniformis reduced (P = 0.05) infectivity on tomato. In field trials, suppression (P = 0.05) of M. incognita was observed 32 DAP by abamectin seed treatment whereas no suppression of R. reniformis was observed. No suppression of M. incognita was perceived by abamectin seed treatment in microplots. Suppression of M. incognita was observed in microplots by harpinEA and harpingαβ as a seed treatment and foliar spray, respectively. Seed cotton yields were variable for abamectin-treated seed, but numerically positive for harpin-treated cotton. Initial gall formation on developing taproots was suppressed (P = 0.001), and penetration of 5-cm long taproots by M. incognita and R. reniformis was numerically suppressed by abamectin-treated compared to non-treated seed, but infection increased with root development. Using an assay of nematode mobility, the proportion of dead second-stage juveniles (J2) was higher (P = 0.05) following exposure to an excised radicle from abamectin-treated seed than non-treated seed, but lower (P = 0.05) than J2 exposed to the abamectin-treated seed coat. Thus a higher concentration of abamectin remained on the seed coat than emerging radicle. The concentration of abamectin transferred from the seed coat to the developing roots was limited, which contributed to the variability in suppression of plant-parasitic nematodes on cotton

Proceedings of the 43rd Annual Meeting, Southern Soybean Disease Workers (March 9-10, 2016, Pensacola Beach, Florida)

Contents Schedule Southern United States Soybean Disease Loss Estimates for 2015. TW Allen, CA Bradley, JP Damicone, NS Dufault, TR Faske, CA Hollier, T Isakeit, RC Kemerait, NM Kleczewski, SR Koenning, HL Mehl, JD Mueller, C Overstreet, PP Price, EJ Sikora, TN Spurlock, and H Young Soilborne Disease Symposium (Tom Allen, moderator) Integrated management of sudden death syndrome. D Mueller, L Leandro, Y Kandel, C Bradley, M Chilvers, A Tenuta, and K Wise Field screening for stem canker: an outdated exercise or a necessary service for soybean growers? K Rowe and T Kirkpatrick Nematode associated diseases in soybean. C Overstreet, Edward C McGawley, D Xavier-Mis, and M Kularathna Characterization of taproot decline in southern soybean. M Tomaso-Peterson, T Allen, P Price, R Singh, and T Spurlock Frontline tactics to manage Phytophthora stem and root rot. A Robertson Graduate student research competition (Travis Faske and Terry Spurlock, moderators) Causative agents for the green stem disorder of soybeans in Louisiana. B Ward, C Robertson, and R Schneider Solubilization of cercosporin and its use for reproducing symptoms of Cercospora leaf blight of soybean. E Silva, M Liu, J Zhang, C Robertson, Z Liu, and R Schneider Effect of droplet size on foliar fungicide application in soybean. S Butler, H Kelly, T Mueller, and G Kruger Virulence assessment of strobilurin-sensitive and -resistant Cercospora sojina, the causal agent of frogeye leaf spot in soybean. N Brochard, M Tomaso-Peterson, T Allen, and R Melanson Application thresholds in controlling Cercospora sojina, the causal agent of frogeye leaf spot. J Jordan and H Kelly Assessment of ILeVO for management of root-knot nematodes in soybean. C Jackson, T Faske, M Emerson, and K Hurd Evaluating the physiological impacts of fungicide phytotoxicity in Mississippi soybean. J Mansour, M Tomaso-Peterson, A Henn., J Bond, T Irby, and T Allen Benefit of secondary nutrition in reducing Macrophomina phaseolina colonization in Mississippi soybean T. Wilkerson, M. Tomaso-Peterson. B Golden, S Lu, A Johnson, and T Allen Detection of a mycovirus from soybean rust and mycoviruses from other biotrophic fungi using a practical method for the extraction of viral dsRNA. R Herschlag, S Khankhum, and R Valverde Effect of Macrophomina phaseolina inoculation, irrigation and cultivar on soybean yield. M Zaccaron and J Rupe Contributed papers (Eduardo Silva, moderator) Phenotypic characterization of Cercospora sojina isolates collected from wide geographical areas. A Mengistu, J Ray, J Smith, and H Kelly Phenotypic characterization of Cercospora sojina isolates collected from wide geographical areas. A Mengistu, J Ray, J Smith, and H Kelly Effect of flower and pod removal on soybean senescence and comparison to green bean syndrome. J Rupe, B Holland, and A Steger Competition studies of QoI resistant and sensitive Cercospora sojina isolates, the causal agent of frogeye leaf spot. B Lin, H Kelly, H Yu, and A Mengistu Frequency and distribution of QoI resistant Cercospora sojina in Virginia. H Mehl and T Zhou A survey of Arkansas soybean nematodes, 2014-2015. K Sullivan, J Robinson, and T Kirkpatrick Nuclear proteins controlling soybean rust resistance B. Cooper Nuts, bolts, frogeye leaf spot, and the UUOT. T Allen, T Faske, C Hollier, P Price, T Spurlock, and H Young Proceedings of the Southern Soybean Disease Workers are published annually by the Southern Soybean Disease Workers. Text, references, figures, and tables are reproduced as they were submitted by authors. The opinions expressed by the participants at this conference are their own and do not necessarily represent those of the Southern Soybean Workers. Mention of a trademark or proprietary products in this publication does not constitute a guarantee, warranty, or endorsement of that product by the Southern Soybean Disease Workers

Coregulation of vascular tube stabilization by endothelial cell TIMP-2 and pericyte TIMP-3

The endothelial cell (EC)–derived tissue inhibitor of metalloproteinase-2 (TIMP-2) and pericyte-derived TIMP-3 are shown to coregulate human capillary tube stabilization following EC–pericyte interactions through a combined ability to block EC tube morphogenesis and regression in three-dimensional collagen matrices. EC–pericyte interactions strongly induce TIMP-3 expression by pericytes, whereas ECs produce TIMP-2 in EC–pericyte cocultures. Using small interfering RNA technology, the suppression of EC TIMP-2 and pericyte TIMP-3 expression leads to capillary tube regression in these cocultures in a matrix metalloproteinase-1 (MMP-1)–, MMP-10–, and ADAM-15 (a disintegrin and metalloproteinase-15)–dependent manner. Furthermore, we show that EC tube morphogenesis (lumen formation and invasion) is primarily controlled by the TIMP-2 and -3 target membrane type (MT) 1 MMP. Additional targets of these inhibitors include MT2-MMP and ADAM-15, which also regulate EC invasion. Mutagenesis experiments reveal that TIMP-3 requires its proteinase inhibitory function to induce tube stabilization. Overall, these data reveal a novel role for both TIMP-2 and -3 in the pericyte-induced stabilization of newly formed vascular networks that are predisposed to undergo regression and reveal specific molecular targets of the inhibitors regulating these events

Geographic Variation in Larval Metabolic Rate Between Northern and Southern Populations of the Invasive Gypsy Moth

Thermal regimes can diverge considerably across the geographic range of a species, and accordingly, populations can vary in their response to changing environmental conditions. Both local adaptation and acclimatization are important mechanisms for ectotherms to maintain homeostasis as environments become thermally stressful, which organisms often experience at their geographic range limits. The spatial spread of the gypsy moth (Lymantria dispar L.) (Lepidoptera: Erebidae) after introduction to North America provides an exemplary system for studying population variation in physiological traits given the gradient of climates encompassed by its current invasive range. This study quantifies differences in resting metabolic rate (RMR) across temperature for four populations of gypsy moth, two from the northern and two from southern regions of their introduced range in North America. Gypsy moth larvae were reared at high and low thermal regimes, and then metabolic activity was monitored at four temperatures using stop-flow respirometry to test for an acclimation response. For all populations, there was a significant increase in RMR as respirometry test temperature increased. Contrary to our expectations, we did not find evidence for metabolic adaptation to colder environments based on our comparisons between northern and southern populations. We also found no evidence for an acclimation response of RMR to rearing temperature for three of the four pairwise comparisons examined. Understanding the thermal sensitivity of metabolic rate in gypsy moth, and understanding the potential for changes in physiology at range extremes, is critical for estimating continued spatial spread of this invasive species both under current and potential future climatic constraints

Meta-analysis of yield response of foliar fungicide-treated hybrid corn in the United States and Ontario, Canada

Foliar fungicide applications to corn (Zea mays L.) occur at one or more application timings ranging from early vegetative growth stages to mid-reproductive stages. Previous studies indicated that fungicide applications are profitable under high disease pressure when applied during the tasseling to silking growth stages. Few comprehensive studies in corn have examined the impact of fungicide applications at an early vegetative growth stage (V6) compared to late application timings (VT) for yield response and return on fungicide investment (ROI) across multiple locations