Reduced Fitness of Virulent Aphis glycines (Hemiptera: Aphididae) Biotypes May Influence the Longevity of Resistance Genes in Soybean

Sustainable use of insect resistance in crops require insect resistance management plans that may include a refuge to limit the spread of virulence to this resistance. However, without a loss of fitness associated with virulence, a refuge may not prevent virulence from becoming fixed within a population of parthenogenetically reproducing insects like aphids. Aphid-resistance in soybeans (i.e., Rag genes) prevent outbreaks of soybean aphid (Aphis glycines), yet four biotypes defined by their capacity to survive on aphid-resistant soybeans (e.g., biotype-2 survives on Rag1 soybean) are found in North America. Although fitness costs are reported for biotype-3 on aphid susceptible and Rag1 soybean, it is not clear if virulence to aphid resistance in general is associated with a decrease in fitness on aphid susceptible soybeans. In laboratory assays, we measured fitness costs for biotype 2, 3 and 4 on an aphid-susceptible soybean cultivar. In addition, we also observed negative cross-resistance for biotype-2 onRag3, and biotype-3 on Rag1 soybean. We utilized a simple deterministic, single-locus, four compartment genetic model to account for the impact of these findings on the frequency of virulence alleles. When a refuge of aphid susceptible was included within this model, fitness costs and negative cross-resistance delayed the increase of virulence alleles when virulence was inherited recessively or additively. If virulence were inherited additively, fitness costs decreased the frequency of virulence. Combined, these results suggest that a refuge may prevent virulent A. glycines biotypes from overcoming Rag genes if this aphid-resistance were used commercially in North America

Determining the duration of Aphis glycines (Hemiptera: Aphididae) induced susceptibility effect in soybean

Insect herbivores can increase the suitability of host plants for conspecifics by inducing susceptibility. Induced susceptibility can be separated into feeding facilitation, whereby herbivore feeding increases performance of conspecifics regardless of the genotype of the herbivore or plant, and obviation of resistance, whereby feeding by a virulent herbivore increases performance of avirulent conspecifics on resistant plants. Both forms occur between Aphis glycines (Hemiptera: Aphididae) and soybean. In natural and agricultural settings, A. glycines populations can colonize plants for brief periods before emigrating or being removed due to predation or insecticides. It is unclear if induced susceptibility lasts beyond the period when A. glycines are present on the plant. We measured the duration of induced susceptibility in the A. glycines-soybean system within a growth chamber by removing inducer populations after 24 h. We used an A. glycines-resistant soybean infested with an inducer population of either virulent, avirulent, or no aphids. Response populations of either virulent or avirulent aphids were added at three post-infestation times (24, 120, 216 h) and their densities measured 11 days after infestation. Feeding facilitation was lost within 24 h of the removal of avirulent inducer populations, and obviation of resistance diminished over time and was completely lost within 216 h of the removal of the virulent inducer populations. We discuss how these results support a hypothesis that virulence in A. glycines is due to effector proteins secreted by feeding aphids. We suggest that the duration of induced susceptibility may impact the durability of A. glycines resistance in soybean

Notes on Recent Cases

Notes on recent cases by Wm. Lee O\u27Malley, T. J. O\u27Neal, James A. Allan, L. A. O\u27Connor, Kenneth Konop, and Austin Gildea

Development of a Soil Carbon Index for Iowa Mineral Soils

A carbon index (Cl) is one of many soil quality indicators that depends on organic carbon concentration. One of the values of a soil carbon index is in determining the impact of agriculture practices (i.e., tillage, crop rotation, N management, etc.) on soil organic matter status of mineral soils. Interactions of climate, parent material, topography, time, and organisms including human activities influence soil organic carbon (SOC). This study developed a soil carbon index for mineral soil map units in Iowa using data collected by the Iowa Cooperative Soil Survey Laboratory and the USDA Soil Survey Laboratory for over 2,300 soil map units across the state in the past 20-30 years. The results show that the soil CI is highly influenced by soil forming factors. The highest soil carbon index was associated with soil map units of soils that are poorly drained, have moderately fine textures, and are on relatively flat topography as in the Clarion-Nicollet-Webster soils association area in north-central Iowa. Additionally, there was a negative correlation between the number of hectares of soils formed under deciduous forest vegetation and CI values within a county. The CI is also related to soil productivity in the state. Fifty five percent of the variability of the corn suitability ratings was explained by the CI. The CI is a valuable tool in evaluating soil organic matter status, productivity of Iowa soils, and land valu

Influence of Invasive Hybrid Cattails on Habitat Use by Common Loons

An invasive hybrid cattail species, Typha x glauca (T. x glauca), is rapidly expanding across the United States and Canada. Dense clonal stands of T. x glauca outcompete native wetland plants, reduce open-water habitats, and negatively affect native wetland plant diversity; however, effects of hybrid cattail expansions on native wildlife are still unclear. We used multiple surveys and single-season occupancy models to examine how the relative coverage of T. x glauca affected habitat use by common loons (Gavia immer) at 71 wetland sites in Voyageurs National Park, Minnesota, USA, during summer 2016. Delineated wetland sites (2 ha) were considered potential resource patches for common loons and positioned along a gradient of relative T. x glauca coverage. Detection of common loons was influenced negatively by the time of day surveys were conducted. Occupancy probabilities were greater at sites with deeper water levels, possibly indicating selection for areas with adequate water depths for pursuit-based foraging for fish. Contrary to our hypothesis, common loons appeared insensitive to the relative coverage of T. x glauca at wetland sites. Future research should focus on elucidating potential threshold-effects of T. x glauca expansions on additional loon demographic rates

Age- and sex-related ABC transporter expression in pyrethroid-susceptible and – resistant \u3ci\u3eAedes aegypti\u3c/i\u3e

Resistance mechanisms to synthetic insecticides often include point mutations and increased expression of genes encoding detoxification enzymes. Since pyrethroids are the main adulticides used against Aedes aegypti, which vectors pathogens such as Zika virus, understanding resistance to this insecticide class is of significant relevance. We focused on adenosine triphosphate (ATP)-binding cassette (ABC) transporters in the pyrethroid-resistant Puerto Rico (PR) strain of Ae. aegypti. We investigated the expression patterns of six ABC transporters previously characterized as differentially expressed in insecticide-challenged mosquitoes, or increased mRNA expression in pyrethroid-resistant Ae. aegypti, by comparing PR to the Rockefeller (Rock) susceptible strain. No constitutive differential expression between strains was detected, but expression differences for these genes was influenced by sex and age, suggesting that their role is independent from resistance in PR. Instead, ABC transporters may be induced after insecticide exposure. Challenging mosquitoes with deltamethrin, with or without ABC transporter modulators, showed that Rock and PR responded differently, but a contribution of ABC transporters to deltamethrin toxicity is suspected. Moreover, the effect of dexamethasone, which enhanced the inhibition of nerve firing by deltamethrin, was observed using a Drosophila central nervous system preparation, showing synergy of these two compounds through the potential inhibition of ABC transporters

Biola Hour Highlights, 1976 - 01

Essentials of Prayer by Al Sanders Titles of the Savior by Richard Chase Historic Reality and Prophetic Promise by Charles Feinberg Celebrating \u27Xmas\u27 by Samuel Sutherland A Unique Christmas by Glenn O\u27Neal Christmas Comparisons from John 12 by Ron Hafer Mary, the Mother of Jesus by Ernie Peirson My Peace I Give to You by Curtis Mitchell Mary by Lloyd Anderson Revelation by Lloyd Anderson Panel Discussion by Richard Chase, Charles Feinberg, and Samuel Sutherlandhttps://digitalcommons.biola.edu/bhhs/1023/thumbnail.jp

Biola Hour Highlights, 1976 - 01

Essentials of Prayer by Al Sanders Titles of the Savior by Richard Chase Historic Reality and Prophetic Promise by Charles Feinberg Celebrating \u27Xmas\u27 by Samuel Sutherland A Unique Christmas by Glenn O\u27Neal Christmas Comparisons from John 12 by Ron Hafer Mary, the Mother of Jesus by Ernie Peirson My Peace I Give to You by Curtis Mitchell Mary by Lloyd Anderson Revelation by Lloyd Anderson Panel Discussion by Richard Chase, Charles Feinberg, and Samuel Sutherlandhttps://digitalcommons.biola.edu/bhhs/1023/thumbnail.jp

Biola Hour Highlights, 1976 - 12

Daniel by Lloyd Anderson I Thessalonians by Lehman Strauss II Thessalonians by Lehman Strauss Faithfulness of God by Lehman Strauss Psalm 131 by Al Sanders Panel Discussion by Richard Chase, Charles Feinberg, and Samuel Sutherlandhttps://digitalcommons.biola.edu/bhhs/1034/thumbnail.jp

Vibronic coupling and band gap trends in CuGeO3 nanorods

We measured the optical response of CuGeO3 nanorods in order to reveal size effects on the electronic properties. The vibronically activated d-to-d color band excitations are activated by the 131 and 478 cm−1 phonons, with the relative contribution of the lower frequency O-Cu-O bending mode increasing with decreasing size until it dominates the process. We also uncover trends in the direct band gap, with the charge transfer edge hardening with decreasing size. These findings advance the understanding of size effects in low-dimensional copper oxides