First Report of Leaf Necrosis on Microstegium vimineum Caused by Bipolaris microstegii in Maryland.

Japanese stiltgrass (JSG, Microstegium vimineum) is an invasive weed causing significant ecological changes in the United States. Severely diseased plants in a shaded location 2 × 4 m in size were discovered in August 2012 at a residence on Indian Springs Rd., Frederick, MD (39.46747° N, 77.46106° W). JSG in larger monoculture stands at sunny locations within 6 to 10 m of diseased plants had a few, small, necrotic spots. Diseased plants had leaves with brown, often large, elliptical, necrotic spots up to 0.5 × 1.5 cm. Lesions were surrounded by a diffuse chlorotic margin, and larger lesions had tan centers. Diseased plants were smaller in stature than neighboring, non-symptomatic plants. Symptoms were similar to those on JSG reported by Kleczewski and Flory (2). Field samples of diseased leaves in moist chambers at room temperature and lighting produced dematiaceous conidiophores and conidia typical of Bipolaris within 2 days. Subcultures of the isolate (FDWSRU 12-049) were made from the conidia. Cultures growing on modified potato carrot agar (broth from 140 g each of potatoes and carrots and 20 g agar in 1 L water), were gray, velutinous or tomentose, and had clumps of short aerial hyphae on the upper surface. Healthy plants were grown in potting soil from seeds collected at the disease site. A minimum of five 4-week-old plants were spray-inoculated in each of three replications by conidia from detached leaves in a suspension of 105 spores/ml, given a 16-h dew period at 25°C, and placed in a 25°C greenhouse for observation. Non-inoculated plants were included for comparison. Brown or dark tan necrotic, irregular, often linear, spots with entire margins developed on all inoculated individual plants and not on control plants. The Bipolaris species was recovered from inoculated plant samples incubated in moist chambers, thus fulfilling Koch's postulates. Conidia were produced sympodially on dematiaceous conidiophores, often in clusters of two to three spores at the terminus, were medium to dark brown, straight or slightly curved, nearly fusiform with obtuse apices, and typically had 8 to 10 distoseptate cells that were 74.8 ± 2.3 × 16.4 ± 0.3 µm, and Q = 4.6 ± 0.1 (mean ± ci, P = 0.05; n = 100). A sequence of the ITS1-5.8S-ITS2 region of DNA, extracted using a DNeasy Plant Mini Kit (QIAGEN), was 100% identical to that of the type specimen of B. microstegii from M. vimineum (BPI 883727; GenBank Accession No. JX089579), using BLAST. On the basis of fungal morphology and molecular characteristics (1), along with symptomatology and published information (2), the causal agent of this disease has been determined to be B. microstegii. Dried specimens of both the isolate and diseased leaves were deposited in the U.S. National Fungus Collections (BPI 892680) and sequence information was submitted to GenBank (KF150215). Bipolaris leaf spot was also found on JSG in Howard and Prince Georges counties, MD, in 2009, but the causal agents were not formally characterized (K. Rane, Univ. Maryland; personal communication). This is the first confirmed identification of B. microstegii on JSG in Maryland, a plant that occurs as extensive monocultures in natural areas. These results provide a basis for characterization of this disease in the mid-Atlantic region. References: (1) P. W. Crous et al. Fungal Planet description sheets: 128-153. Persoonia 29:146, 2012. (2) N. M. Kleczewski and S. L. Flory. Plant Dis. 94:807, 2010.

Cloud images from the pioneer venus orbiter.

Ultraviolet images of Venus over a 3-month period show marked evolution of the planetary scale features in the cloud patterns. The dark horizontal Y feature recurs quasi-periodically, at intervals of about 4 days, but it has also been absent for periods of several weeks. Bow-shaped features observed in Pioneer Venus images are farther upstream from the subsolar point than those in Mariner 10 images.

Orbiter cloud photopolarimeter investigation.

The first polarization measurements of the orbiter cloud photopolarimeter have detected a planet-wide layer of submicrometer aerosols of substantial visible optical thickness, of the order of 0.05 to 0.1, in the lower stratosphere well above the main visible sulfuric acid cloud layer. Early images show a number of features observed by Mariner 10 in 1974, including planetary scale markings that propagate around the planet in the retrograde sense at roughly 100 meters per second and bright- and dark-rimmed cells suggesting convective activity at low latitudes. The polar regions are covered by bright clouds down to latitudes aproximately 50 degrees, with both caps significantly brighter (relative to low latitudes) than the south polar cloud observed by Mariner 10. The cellular features, often organized into clusters with large horizontal scale, exist also at mid-latitudes, and include at least one case in which a cell cuts across the edge of the bright polar cloud of the northern hemisphere.

Development of a capacitive immunosensor: a comparison of monoclonal and polyclonal capture antibodies as the primary layer.

There is widespread interest in capacitance immunosensor systems which directly detect antigen binding to immobilized antibody. Our system comprises an active biolayer of antibodies bound to a silicon--silicon dioxide--silicon nitride (Si-SiO2-Si3N4) surface. As with other groups, our system initially gave poorly reproducible responses on addition of antigen. We mechanically degraded the Si-SiO2-Si3N4 surface, and the responses on addition of transferrin were monitored. The mechanical degradation allowed the affinity reaction to be 'seen' capacitively. Once the system was established, a comparison of capture antibodies was performed to establish the most effective biolayer. Three affinity reactions were examined: (a) 1D2A4, monoclonal antibody (mAb) to human transferrin, as the capture layer; (b) polyclonal goat anti-human transferrin antibody (PcAb) as the capture layer; and (c) 1D2A4 with transferrin (Tf) prebound as the capture layer. There was no response to addition of transferrin where 1D2A4 was the capture layer. Addition of transferrin when the polyclonal antibody was used as the primary layer resulted in a drop in measured capacitance. Addition of goat anti-human transferrin antibody to a device with 1D2A4 plus transferrin as the capture layer also resulted in a measured capacitance decrease. There is a difference in dielectric/blocking effectiveness between the monoclonal and polyclonal antibodies.