The pathogenicity and seasonal development of Gymnosporangium in Iowa

Seven species of the genus Gymnosporangium occur in Iowa, but only G. juniperi-virginianae, causing cedar-apple rust, and G. globosum, causing hawthorn rust, are common. The latter is of little economic importance. The epidemic of cedar-apple rust in 1928 caused an estimated loss of $200,000 in Iowa. Six to seven hours were required to produce abundant sporulation from air dry galls of G. juniperi-virginianae regardless of whether the period of soaking was 30 or 180 minutes. Newly-matured aecidiospores of G. juniperi-virginianae germinated to the extent of 54 percent in July. A lot was divided and the percentage of germination in the portion refrigerated at 5 to 13°C. increased rapidly for at least 22 days, while that in the portion held at room temperature for the same interval dropped to zero. At Shenandoah the interval between infection and first opening of aecidia of cedar-apple rust on Bechtel\u27s flowering crab was about 72 days. That for hawthorn rust on Crataegus mollis was about 81 days. Seedlings of red cedar were successfully inoculated using aecidiospores of G. juniperi-virginianae. Large differences in the number of galls on trees which had received similar treatments suggested a variation in disease resistance. The only appreciable germination of aecidiospores of G. globosum was obtained in November from diseased hawthorn leaves which had fallen to the ground and others which were refrigerated 41 days at 5°C. Differences in the degree of maturity reached by the cedar rusts are utilized in defining the relative susceptibility of their aecidial hosts. The percentage of leaf area covered by lesions of cedar-apple rust is recorded for 138 varieties of apples and 28 varieties of crabapples which were growing in nursery rows at Shenandoah during the years, 1928 to 1930. Aecidiospores were matured on only 30 percent of these hosts. The percentage of infected apple leaves seemed to vary roughly as the percentage. of diseased leaf area, but leafiness was not related to the amount of rust infection. These lines of evidence suggest that the period of susceptibility in leaves of susceptible varieties may be longer than that of resistant ones. Artificial inoculations show that Tolman and York Imperial varieties of apple are very susceptible to the strain of G. juniperi-virginianae from Morgantown, W. Va., but are resistant to other strains from Ames and Shenandoah, Iowa; Manhattan, Kan., and Cochrane, ,Vis. The results indicate the presence of physiologic specialization within the species. There is little evidence that the susceptibility of trees of one variety of apple may vary in different sections of the country. None of the observed varieties of apple or crabapple seem to be susceptible to G. globosum, in Iowa

Control of cherry yellow-leaf on nursery stock

Yellow-leaf, caused by the fungus Coccomyces hiemalis Higgins, is the most prevalent and destructive cherry disease in Iowa, since it often causes premature defoliation of both nursery and orchard trees. Early defoliation in nursery stock results in decreased growth during the current and subsequent years, and precludes all possibility of forcing the trees into marketable size in one growing season. In the orchard, defoliation may decrease fruit bud formation and vegetative growth and increase the amount of winterkilling. All defoliated nursery stock must be held in the nursery row a second season, and even then many of the trees must be marketed at lower grades because of inferior size. Winterkilling in severely defoliated blocks is so common that yellow-leaf becomes the limiting factor in cherry culture

A study of Sclerospora Graminicola (Sacc.) Schroet. on Setaria Viridis (L.) Beauv. and Zea Mays L.

Conidial sporulation of Sclerospora graminicola has been observed in the day time occurring naturally in the field and under artificial conditions in the laboratory. The period required for the development of mature conidia lies between 4 hours 35 minutes and 111/2 hours. The conditions which seem necessary for the production of conidia, whether during the day or night, are: a completely saturated atmosphere, turgid host leaves, a slight moisture film on the surface of the leaves and a temperature ranging between 8° and 27 °C. When flooded into a drop of water immediately after being discharged, conidia were found to germinate after 60 minutes. The best germination was obtained at 15°C., but the optimum was not definitely determined. Normal conidia measure 14-23 x 11-17µ. Sometimes larger conidia are produced (43 x 18.6µ) . The average length of conidiophores of Sclerospora graminicola was found to be 267.8µ while the individuals measured ranged from 214.5 to 375.3µ, a variation of 160.8µ. Spores were found to be forcefully discharged from the conidiophores thru a distance of 2.5 mm. vertically and 1.89 mm. horizontally. Setaria viridis, S. italica, Zea mays (May\u27s Golden popcorn) and Euchlaena mexicana were infected with Sclerospora graminicola when exposed to the conidia of the mildew. Oospores of Sclerospora graminicola were found to overwinter naturally in field soil under Iowa conditions. In one test, oospores which overwintered outdoors gave nearly twice as much infection on Setaria viridis and Zea Mays (Japanese Hulless popcorn) as did the oospores which were kept in the laboratory, Plants from five genera of Gramineae were found to be susceptible hosts to Sclerospora graminicola. These are: Euchlaena, Setaria, Holcus, Saccharum and Zea. Setaria viridis was found to be the most susceptible of all hosts and popcorn more susceptible than sweet corn and dent corn. Six days were found to be the usual period of incubation between the time oospores were placed on the seeds and that when conidial fruiting appeared on the leaves. Infection by oospores was obtained from the time the testa was broken until the emergence of the plumule above ground. Relative susceptibility of seedlings decreases with age. The processes connected with infection are more greatly favored by temperatures of 15° to 16°C. than by temperatures of 24° to 30°C. The germinating oospore is evidently unable to penetrate older leaf tissue. The viability of oospores was little affected by soaking in 2 percent copper sulfate solutions for 10 minutes, while similar treatment in 1 percent formaldehyde for 5 minutes proved fatal. The killing action of mercuric chloride 1-1000 was not so great as that of formaldehyde. Freshly collected oospores which were held in a dry condition at 77°C. for 1 hour later gave 52 percent infection on Setaria viridis, while wet spores lost their viability to a marked degree when held at 50°C. for a similar period. Sclerospora graminicola was studied in the field during the summers of 1925, 1926 and 1927. Infection was obtained on corn and teosinte planted in plots which had been artificially infested with oospores. Spontaneous conidial sporulation was found to be comparatively rare on corn in the field altho it was observed in 1926 and 1927 on young seedlings during periods of high humidity and cool temperatures. Infected plants were either killed outright or became stunted and unproductive. A few plants apparently outgrew the attack. In Iowa, Sclerospora graminicola has been observed only twice occurring naturally on corn in the field. Oospores of Sclerospora graminicola which had been held 30 months under dry conditions in the laboratory were found to be viable. Presoaking of oospores does not seem to affect the percentage of infection. Soil is not necessary as a medium for the germination of oospores

Current Single Event Effect Test Results for Candidate Spacecraft Electronics

Abstract We present both proton and heavy ion single event effect (SEE) ground test results for candidate spacecraft electronics. A variety of digital and analog devices were tested, including EEPROMs, DRAMs, and DC-DC Converters

Determination of Molecular Structures of HIV Envelope Glycoproteins using Cryo-Electron Tomography and Automated Sub-tomogram Averaging

Since its discovery nearly 30 years ago, more than 60 million people have been infected with the human immunodeficiency virus (HIV) (www.usaid.gov). The virus infects and destroys CD4+ T-cells thereby crippling the immune system, and causing an acquired immunodeficiency syndrome (AIDS) 2. Infection begins when the HIV Envelope glycoprotein "spike" makes contact with the CD4 receptor on the surface of the CD4+ T-cell. This interaction induces a conformational change in the spike, which promotes interaction with a second cell surface co-receptor 5,9. The significance of these protein interactions in the HIV infection pathway makes them of profound importance in fundamental HIV research, and in the pursuit of an HIV vaccine

Ion-Abrasion Scanning Electron Microscopy Reveals Surface-Connected Tubular Conduits in HIV-Infected Macrophages

HIV-1-containing internal compartments are readily detected in images of thin sections from infected cells using conventional transmission electron microscopy, but the origin, connectivity, and 3D distribution of these compartments has remained controversial. Here, we report the 3D distribution of viruses in HIV-1-infected primary human macrophages using cryo-electron tomography and ion-abrasion scanning electron microscopy (IA-SEM), a recently developed approach for nanoscale 3D imaging of whole cells. Using IA-SEM, we show the presence of an extensive network of HIV-1-containing tubular compartments in infected macrophages, with diameters of ∼150–200 nm, and lengths of up to ∼5 µm that extend to the cell surface from vesicular compartments that contain assembling HIV-1 virions. These types of surface-connected tubular compartments are not observed in T cells infected with the 29/31 KE Gag-matrix mutant where the virus is targeted to multi-vesicular bodies and released into the extracellular medium. IA-SEM imaging also allows visualization of large sheet-like structures that extend outward from the surfaces of macrophages, which may bend and fold back to allow continual creation of viral compartments and virion-lined channels. This potential mechanism for efficient virus trafficking between the cell surface and interior may represent a subversion of pre-existing vesicular machinery for antigen capture, processing, sequestration, and presentation

An effect of eyestalk ablation on antennular function in the spiny lobster, Panulirus argus

1. Unilateral removal of the eyestalk (optic ganglia and medulla terminalis) in the Bermuda spiny lobster, Panulirus argus , disrupts normal initiation of feeding activity via chemo-tactile stimulation of the antennule on the side of the ablation. This deficit may be permanent for it has lasted without apparent remission for over five months and two molts. Unilateral eyestalk ablation also produces a temporary increase in antennular cleaning activity directed toward the antennule on the side of the ablation. This effect seems to last for less than 16 days. Unilateral eyestalk ablation does not appreciably disturb spontaneous antennular movements or responses to mechanical stimulation of the antennule on either side. Nor does it destroy the ability of the lobster to give differential responses to mechanical and chemo-tactile stimuli. Most lobsters recover normal sensory and motor functions in antennules that regenerate after amputation of the distal segment and sensory flagellae. In about 1/3 of the animals, however, some form of sensory or motor abnormality is evident in the regenerated antennule. These deficits are ascribed to occasional failure of regenerating neurons to reform appropriate central connections. They do not resemble the deficits following eyestalk ablation. The medulla terminalis is tentatively proposed as the portion of the nervous system critical for normal antennular function that is removed by eyestalk ablation. There seem to be similarities between the effects of eyestalk ablation in the Crustacea as described here and the effects following destruction of portions of the corpora pedunculata in insects. 1. Einseitige Entfernung des Augenstieles (optische Ganglien und Medulla terminalis) bei der Bermuda-Stachellanguste, Panulirus argus , unterbricht auf der operierten Seite den Beginn der normalen Freß-tätigkeit, die durch chemische und taktile Reizung der Antennula eingeleitet wird. Diese Störung kann irreversibel sein, denn sie überdauerte in über 5 Monaten zwei Häutungen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47096/1/359_2004_Article_BF00340474.pd