Bruce F. Ingber

The effects of selected cotton-leaf volatiles on growth, development and aflatoxin production of Aspergillus parasiticus

The fungi Aspergillus flavus and Aspergillus parasiticus produce the hepatocarcinogenic, secondary metabolites, aflatoxins, in cottonseed, corn, peanuts and treenuts. Results have shown that aflatoxigenic strains of A. flavus and A. parasiticus grown in the presence of specific cotton-leaf volatiles exhibit alterations in aflatoxin production accompanied by variations in growth of the fungi. In this study, two alcohols (3-methyl-1-butanol (3-MB) and nonanol) and two terpenes (camphene and limonene) were chosen as representative cotton-leaf volatiles based on the effects they had on fungal growth and/ or aflatoxin production in previous investigations. The morphological effects of volatile exposure were examined in correlation with fungal growth and aflatoxin production. 3-MB-treated samples exhibited a decrease in fungal radial growth which was directly proportional to the volatile dosage. Additionally, 3-MB treatment resulted in loss of mycelial pigmentation and a decrease in sporulation. Limonene and camphene-treated samples yielded negligible differences in radial growth and morphology when compared to unexposed controls. In addition to radial growth inhibition, samples grown in the presence of nonanol demonstrated uniquely aerial hyphae. In comparison to an unexposed control, aflatoxin production increased in cultures exposed to 3-MB but decreased when exposed to the other three volatiles studied.

Structure of Spermatheca, Sperm Dynamics, and Associated Bacteria in Formosan Subterranean Termite (Isoptera: Rhinotermitidae)

Abstract Primary reproductives of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), complete their first reproductive cycle in ≈60 d after nest formation. During this period, the pairs mate several times. The spherical, aflagellate sperm, after transfer by the male, are stored in the female’s spermatheca. Sperm numbers in the spermatheca increase significantly between day 20 and 40, and thereafter they show a steep decline, indicating that the pairs may not be mating after day 40. The spermatheca is bean shaped with an extremely narrow duct. The thick wall of the spermatheca consists mainly of type 3 cells made up of secretory and duct cells. Cuticle-lined ducts are interspersed throughout these cells. Finger-like extensions of the cuticle-lined interior wall project into the spermathecal lumen. The secretory cells presumably provide nutrition for the sperm during their long storage. Eleven anaerobic and six aerobic species of bacteria were cultured and identified from the spermatheca. The role of these bacteria is unknown.

A Dehydration Method for Immature or Wet Cotton Fibers for Light and Electron Microscopy

A rapid dehydration procedure with acidified 2,2-dimethoxypropane (DMP) has been successfully applied to immature or wet cotton fibers. The ultrastructural integrity and fiber quality parameters such as cell wall area and perimeter of developing and mature cotton fibers were well-pre-served using this procedure as demonstrated by light, scanning and electron microscopy of whole fibers and cross-sections. Embedding in resin following DMP dehydration also prevented the collapse of the immature fibers due to drying of lumen.

Antifungal Properties of Wheat Histones (H1-H4) and Purified Wheat Histone H1

Wheat ( Triticum spp.) histones H1, H2, H3, and H4 were extracted, and H1 was further purified. The effect of these histones on specific fungi that may or may not be pathogenic to wheat was determined. These fungi included Aspergillus flavus , Aspergillus fumigatus , Aspergillus niger , Fusarium oxysporum , Fusarium verticillioides , Fusarium solani , Fusarium graminearum , Penicillium digitatum , Penicillium italicum , and Greeneria uvicola . Non-germinated and germinating conidia of these fungi were bioassayed separately. The non-germinated and germinating conidia of all Fusarium species were highly susceptible to the mixture (H1-H4) as well as pure H1, with viability losses of 99-100% found to be significant (p < 0.001) at ≤10 μM or less for the histone mixture and pure H1. F. graminearum was the most sensitive to histone activity. The histones were inactive against all of the non-germinated Penicillium spp. conidia. However, they significantly reduced the viability of the germinating conidia of the Penicillium spp. conidia, with 95% loss at 2.5 μM. Non-germinated and germinating conidia viability of the Aspergillus spp. and G. uvicola were unaffected when exposed to histones up to 10 μM. Results indicate that Fusarium spp. pathogenic to wheat are susceptible to wheat histones, indicating that these proteins may be a resistance mechanism in wheat against fungal infection.

The Influence of Cotton Seed Weight on Fibers Per Seed and Fiber Property Uniformity

ABSTRACT Increasing cotton (Gossypium hirsutum L.) fiber weight per seed in some genotypes has the potential to increase micronaire values to levels that trigger price discounts. Strategies need to be developed that limit cell wall deposition. Seed weight decreases as the number of seeds per boll increases. Characterization of the relationship between seed weight, fibers per seed and fiber properties will supply basic information for strategy development. Stoneville 474 and FiberMax 832 were grown under irrigated conditions in 1998 and 1999. First position flowers were harvested on the day of anthesis for fiber density and perimeter analysis. Remaining first position bolls were harvested after boll opening and bolls were individually analyzed for weight and fiber properties. Initial fiber densities were similar for both cultivars. Mean fiber length and cell wall thickness were positively correlated with final seed weight. Fiber length variability decreased as seed weight increased. The decrease in length variability paralleled an increase in fiber cell wall thickness. Strategies to increase the number of seeds per boll may reduce micronaire values but increase length variability.

Biodeterioration of Nonwoven Fabrics

The use of nonwoven fabrics in disposable, convenience products generates high quantities of wastes that are not biodegradable. Synthetic fibers provide a major source of materials for these disposable products. Because synthetics are generally less bio degradable than natural fibers, it appears that for maximum degradability, natural fibers are a likely choice of materials for disposable goods. To compare rates of bio deterioration for natural and synthetic fibers, we examined changes in the structure and strength of nonwoven fabrics containing cotton and polypropylene, a synthetic fiber widely used in nonwovens, after controlled exposure of fabrics to fungi normally found in soil. Fungi grew extensively only on cotton fibers. Fungal growth rates were highest on 100% cotton and decreased to zero on 100% polypropylene. Significant losses in strength occurred only in samples with a high cotton content. Progression of cotton fiber deterioration was followed using the microscope until only polypropylene . fibers remained in the fabrics.

Infection of the formosan subterranean termite, Coptotermes formosanus Shiraki, by the entomopathogenic fungus Isaria fumosorosea

this study investigates Isaria fumosorosea (Ifr) infection of and transfer among Formosan subterranean termites (FST). Prior to fungal exposure nestmates were fed Nile Blue, dye or Neutral Red dye. Blue FST were exposed to 6.3 x 109 fungal spores and mixed with red nestmates. At timepoints up to 168 h, termites were removed from each dyed group and fixed with osmium tetroxide. SEM observation at 24 h post-exposure showed most fungal conidia ungerminated and on the external cuticle of blue FST. At 48 h, germ tubes had formed on blue FST and penetrated the cuticle. Hyphae were observed externally at 96 h post-exposure. Fungal spores were visible on red FSt 96 h after placement with blue FSt, and hyphae were abundant at 168 h post-exposure. Blue FST were fixed, dehydrated, then embedded with a low viscosity epoxy. Embedded FST were sectioned with a microtome and visualized via light microscopy. Ifr penetrated the cuticle of blue FST at 48 h and were found on the interior of termites after 72 h. Transfer to red FST was confirmed 96 h post-exposure through visualization of spores.

Preliminary examination of the effects of relative humidity on the fracture morphology of cotton flat bundles

A preliminary examination of the effects of relative humidity (RH) of three testing conditions on cotton fiber fracture morphology is presented herein. In addition, measurements of fiber moisture content, stelometer cotton flat bundle strength and elongation were collected at the three testing conditions. A general trend is observed for moisture content, strength and elongations measurements; testing in conditions with higher RH generally resulted in a progressive increase in moisture content, strength and elongation values. The morphology of broken fibers was also affected by the testing conditions. Fibers broken at high RH (i.e. 70 ± 2°F and 80 ± 2% RH) showed a more frayed fracture where microfibril separation, a fracture pattern that suggests independent microfibril failure, was evident. In contrast, at standard conditions (i.e. 70 ± 2°F and 65 ± 2%), fiber fractures were more granular (clean fractures), a reflection of a more unilateral breaking action. At low RH (i.e. 70 ± 2°F and 50 ± 2%), fiber fractures exhibited a distorted granular pattern, with extended fracture breaks that did not exhibit microfibril separation. Our preliminary findings are of relevance to post-harvest moisture control efforts currently employed in industry and may contribute to larger efforts to understand the effects of the fracture and damage observed in cotton fiber properties.