Anatomical Characterization of Western Corn Rootworm Damage in Adventitious Roots of Maize

Corn rootworms are one of the most economically damaging insect pests of maize, yet little is known about the feeding behavior of the larvae. This study was conducted to determine which tissues of the adventitious roots of maize are damaged by western corn rootworm (Diabrotica virgifera virgifera LeConte) larval feeding. Root axes (10 cm long) were removed from the fifth node of greenhouse-grown maize plants. Root segments 2 cm long, excised 4 or 6 cm from the root tip, were infested with second or third stage larvae, respectively, (0, 1, 3, or 6 larvae per segment) for a period of 24 hours. Root segments were fixed, embedded and sectioned to a thickness of 16 μm for light microscopy. Serial sections taken at 1 mm intervals were used to measure the amount of tissue removed during insect feeding. Light micrographs revealed that larval feeding damage was restricted to the root cortex, and no damage was visible in the pith. Up to 80% of the cortex was removed during feeding within a 24-h period. The suberized and lignified secondary walls of the endodermis and exodermis appear to act as barriers that either prevent or discourage larval feeding within the pith. These results are discussed in terms of possible explanations of the characteristics of corn rootworm damage under field conditions

Diversity and Dominant Species of Ground Beetle Assemblages (Coleoptera: Carabidae) in Crop Rotation and Chemical Input Systems for the Northern Great Plains

Dominant carabid species present in crops and crop rotation sequences commonly used in the northern Great Plains were assessed as an initial step toward the management of carabids as natural control agents. Ground beetle populations were determined by pitfall trapping in 4 crop rotation treatments maintained under high, managed, and low levels of chemical fertilizer and pesticide inputs. Diversity and species richness among crops, rotations, and input levels were compared using 3 indices—the Shannon-Weaver Index, relative diversity, and the Hierarchical Richness Index (HRI). Four carabid species, Cyclotrachelus altemans (Casey), Poecilvs lucublandus Say, Harpalns pensylvanicus (DeGeer), and Bembidion quadrimaculatum L., comprising ≈80% of the total collected, were considered dominant species. When carabid abundance data were grouped by crop, C. altemans was the dominant species in corn and alfalfa and P. lucublandus was dominant in wheat. In soybean plots, C. altemans and P. lucublandus were equally abundant. The relative abundance of H. pensylvanicus was highest in the low-input plots. High values of HRI for carabid diversity and species richness in the managed plots suggested that reduced chemical inputs encouraged greater abundance and diversity of beneficial carabids than were found in the high-input plots without the loss of yield seen in the low-input plots

Diversity and Dominant Species of Ground Beetle Assemblages (Coleoptera: Carabidae) in Crop Rotation and Chemical Input Systems for the Northern Great Plains

Dominant carabid species present in crops and crop rotation sequences commonly used in the northern Great Plains were assessed as an initial step toward the management of carabids as natural control agents. Ground beetle populations were determined by pitfall trapping in 4 crop rotation treatments maintained under high, managed, and low levels of chemical fertilizer and pesticide inputs. Diversity and species richness among crops, rotations, and input levels were compared using 3 indices—the Shannon-Weaver Index, relative diversity, and the Hierarchical Richness Index (HRI). Four carabid species, Cyclotrachelus altemans (Casey), Poecilvs lucublandus Say, Harpalns pensylvanicus (DeGeer), and Bembidion quadrimaculatum L., comprising ≈80% of the total collected, were considered dominant species. When carabid abundance data were grouped by crop, C. altemans was the dominant species in corn and alfalfa and P. lucublandus was dominant in wheat. In soybean plots, C. altemans and P. lucublandus were equally abundant. The relative abundance of H. pensylvanicus was highest in the low-input plots. High values of HRI for carabid diversity and species richness in the managed plots suggested that reduced chemical inputs encouraged greater abundance and diversity of beneficial carabids than were found in the high-input plots without the loss of yield seen in the low-input plots

Investigation of Griffithsin's Interactions with Human Cells Confirms Its Outstanding Safety and Efficacy Profile as a Microbicide Candidate

Many natural product-derived lectins such as the red algal lectin griffithsin (GRFT) have potent in vitro activity against viruses that display dense clusters of oligomannose N-linked glycans (NLG) on their surface envelope glycoproteins. However, since oligomannose NLG are also found on some host proteins it is possible that treatment with antiviral lectins may trigger undesirable side effects. For other antiviral lectins such as concanavalin A, banana lectin and cyanovirin-N (CV-N), interactions between the lectin and as yet undescribed cellular moieties have been reported to induce undesirable side effects including secretion of inflammatory cytokines and activation of host T-cells. We show that GRFT, unlike CV-N, binds the surface of human epithelial and peripheral blood mononuclear cells (PBMC) through an exclusively oligosaccharide-dependent interaction. In contrast to several other antiviral lectins however, GRFT treatment induces only minimal changes in secretion of inflammatory cytokines and chemokines by epithelial cells or human PBMC, has no measureable effect on cell viability and does not significantly upregulate markers of T-cell activation. In addition, GRFT appears to retain antiviral activity once bound to the surface of PBMC. Finally, RNA microarray studies show that, while CV-N and ConA regulate expression of a multitude of cellular genes, GRFT treatment effects only minimal alterations in the gene expression profile of a human ectocervical cell line. These studies indicate that GRFT has an outstanding safety profile with little evidence of induced toxicity, T-cell activation or deleterious immunological consequence, unique attributes for a natural product-derived lectin

An ultrastructural study of chloroplasts and microbodies in seed and seedling cotyledons of Pharbitis nil

Includes bibliographical references.Includes illustrations.The cellular ultrastructure of cotyledon tissue from seeds and seedlings of Japanese morning glory (Pharbitis nil) was studied. Weight determinations of the seed and seedling cotyledons, the same age as those studied under the transmission electron microscope, indicate that the growing cotyledons of the seed and seedling increase in biomass. During this period of growth, cellular ultrastructure of the seed and seedling cotyledons undergo marked changes. Cells of the seed cotyledon 17 days after anthesis appear as highly vacuolate cells. The appearance of lipid and protein bodies in the cells of slightly older (30 days after anthesis) seed cotyledons corresponds to an increase in fresh weight and percentage dry weight of these slightly older seed cotyledons. Upon dark germination and subsequent irradiation with white light, the fresh weight of the seedling cotyledons increases steadily. Microbodies (glyoxysomes), which aid in the enzymatic breakdown of stored lipid, are present within the dark germinated seedling cotyledon cells. Irradiation of the seedling cotyledons with white light causes the de novo development of the peroxisomes. A description of the ultrastructure of the two types of microbodies, as well as semi-quantitative analysis of their characteristic associations with lipid bodies and chloroplasts is given. Chloroplasts of seed and seedling cotyledons, which undergo developmental changes when exposed to light, were also studied. The ultrastructural appearance of the chloroplasts, as well as the amount of chlorophyll present in seed and seedling cotyledons, indicate that the chloroplasts of both seed and seedling cotyledons are able to carry on the process of photosynthesis. Plastids of dark grown seedling cotyledon cells which were irradiated with continuous far red light undergo no structural transformation.M.S. (Master of Science

One Plus One Equals Three: The Synergistic Effects Of Crop Rotation On Soil Fertility And Plant Nutrition

Corn grown under annual corn-soybean crop rotation has greater accumulation of certain mineral nutrients and higher yields than corn grown in monoculture. This study was conducted to determine if complex crop rotations (with legumes in the rotation as alfalfa hay as well as soybean row crops) and different levels of agriculture chemical input affect soil fertility and corn mineral nutrient composition. The effects of crop rotation [monoculture corn, corn-soybean 2-yr rotation, corn-soybean- wheat underseeded with alfalfa-alfalfa 4-yr rotation] and input level [high input (fertilizer application for 8.15 Mg ha-1 yield goal, prophylactic herbicide and insecticide application, fall moldboard plow/spring disk and cultivation operations), intermediate input (fertilizer application for 5.33 Mg ha-1 yield goal, pesticide applications based upon pest survey and IPM principles, fall chisel plow/spring disk and cultivation operations), and low input (no fertilizer, herbicide, or insecticide applications, fall chisel plow/spring disk and cultivation operations)] on soil fertility (pH, organic matter, NO3-N, P, K, and total N) and on corn shoot dry weight, mineral nutrient (N, P, Ca, Mg) concentration and accumulation at tassel stage of development were investigated at Brookings, SD. Soil samples taken at the V6 stage of corn development indicated that crop rotation treatments reduced soil pH, increased soil NO3-N level, and decreased soil P level when compared to corn monoculture. Shoots of plants grown under either 2-yr rotation intermediate input or 4-yr rotation no input treatments had greater dry weight, as well as greater P, Ca, and Mg accumulation than these same input treatments in other rotations. These results demonstrate a beneficial effect of crop rotation upon soil fertility and corn mineral nutrition. The results of this experiment are discussed in terms of nutrient synergisms whereby nutrient absorption proceeds at a faster rate than dry weight accumulation

Soil Carbon, Nitrogen Use, And Water Use Affected By Rotation In The Northern Corn Belt

Diversified crop rotation may improve production efficiency, reduce fertilizer nitrogen (N) requirements for com (Zea mays L.) and increase soil carbon (C) storage. Objectives were to determine effect of rotation and fertilizer N on soil C sequestration, water use, and N use. An experiment was started in 1990 on a Barnes clay loam (fine-loamy, mixed, superactive, frigid Calcic Hapludoll) near Brookings, South Dakota. Primary tillage on all rotations was with a chisel plow. Rotations were continuous com (CC), com-soybean [Glycine max (L.) Merr.] (CS) and a 4-year rotation of corn-soybean-wheat (Triticum aestivum L.) companion seeded with alfalfa (Medicago sativa L.)-alfalfa hay (CSWA). Additional treatments included plots of perennial warm season, cool season, and mixtures of warm and cool season grasses. N treatments for com were: com fertilized for a grain yield of 8.5 Mg ha-1 (high N), 5.3 Mg ha-1 (midN), and no N fertilizer (noN). Average com grain yield (1996-2001) was not different among rotations at 7.1 Mg ha-1 under highN. Com yield differences among rotations increased with decreased fertilizer N. Average (1996-2001) com yield with noN fertilizer were 7.3 Mg ha-1 under CSWA, 6.1 Mg ha-1 under CS, and 3.8 Mg ha- l under CC. Rotation did not improve N use efficiency (NUE) or water use efficiency (WUE) under highN. With midN, NUE and WUE was about 40% greater under CSWA compared with CC. Plant carbon return depended on rotation and N. In the past 10 years, total C returned from above ground biomass were 29.8 Mg ha-I under CC with highN and 12.8 Mg ha- l under CSWA with noN. Soil C in the top 15 cm significantly increased (0.7 g kg- l) with perennial grass cover but decreased (1.7 g kg- l) under CC, CS, and CSWA. C/N ratio significantly narrowed (-0.75) with CSWA and widened (0.72) under grass. Diversified rotations have potential to increase N use efficiency and reduce fertilizer N input for com. However, within a com production system using conventional tillage and producing (averaged across rotation and N treatment) about 6.2 Mg ha- l com grain per year, we found no gain in soil C after 10 years regardless of rotation

Corn and Soil Fertility Responses to Crop Rotation with Low, Medium, or High Inputs

Corn (Zea mays L.) grown in annual rotation with soybean [Glycine max (L.) Merr.] has greater mineral nutrient accumulation and higher yields than corn grown in monoculture. This study was conducted to determine how crop rotation (continuous corn vs. corn rotated with soybean) with different input levels (tillage, herbicide, insecticide, and fertilizer rates varied to achieve high, intermediate, and low treatments) affected corn shoot dry weight, mineral nutrient (N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn) composition at tasseling, pregrowing-season soil fertility (pH, organic matter, NO−3-N, P, K, and total N), and grain yield on a Vienna loam (fine-loamy, mixed Udic Haploboroll) near Brookings, SD. Crop rotation increased total soil N and NO−3-N but decreased P when compared with continuous corn. The high input treatment resulted in higher soil NO−3-N levels than either the intermediate or low input treatments. Rotation with intermediate input increased corn shoot dry weight and P, K, and Ca accumulation compared with continuous corn with intermediate input. Grain yield responded differently to input levels within the two rotations. Corn yield following soybean was 32% greater than for continuous corn with intermediate inputs, but with high input levels there was no difference between rotation treatments. These results suggest that the level of inputs provided for com can affect the crop rotation response