ARS Assists in Fight Against Kudzu Bug

Sure, this distant relative of the brown marmorated stink bug will feed voraciously on the stems of kudzu, the “Vine That Ate the South.” But Megacopta cribraria also has a taste for soybean and other legumes. In Georgia, where this native of Asia was first discovered in the United States in October 2009, there’s worry that the pest will set its sights on peanut, endangering a $2 billion crop that supplies nearly 50 percent of America’s peanuts (Georgia Peanut Commission, 2009). Like the brown marmorated stink bug, Megacopta—also known as the “bean plataspid”—seeks shelter inside homes, buildings, and vehicles during the fall as temperatures cool. And when disturbed, it too emits a foul smell. Researchers, however, haven’t been idle. For example, at the Agricultural Research Service’s Stoneville [Mississippi] Quarantine Research Facility, entomologist Walker Jones is evaluating a secret weapon in the form of Paratelenomus saccharalis, a tiny black wasp received, under permit, from Japan in 2011

Crop-Friendly Bacteria Tapped To Battle Fungal Marauders

Soil-dwelling bacteria that depend on wheat and barley roots for their “room and board” could soon make good on their debt. Researchers are investigating the microbes’ potential to biologically control root-rot fungi that cause crop yield losses of 10-30 percent annually in the U.S. Pacific Northwest and other parts of the world. The bacteria are members of the genus Pseudomonas and include 11 strains that stymie the growth of Pythium and Rhizoctonia fungi, which are responsible for dampingoff and root-rot diseases of wheat and barley. The pathogens thrive in cool, moist soils and can reach especially high levels in crop fields where conservation tillage is practiced to save on fuel costs, avoid soil erosion, and attain other ecological and environmental benefits. “They’re most problematic to seedlings of spring crops that are 4 to 6 weeks old,” notes Pat Okubara, a geneticist in the Agricultural Research Service’s Root Diseases and Biological Control Research Unit in Pullman, Washington. “Fungicides are not very effective, and there are no resistant wheat or barley varieties yet,” she adds. Rotating wheat with nonhost crops is difficult too, because of the fungi’s extensive plant-host range. Over the past year, Okubara and university colleagues have evaluated the biocontrol potential of 26 Pseudomonas strains. From those, they chose 11 for further study based on 3 important characteristics: rapid colonization of and persistence on roots, high antifungal activity, and reduction of plant disease symptoms

Fire Ant Venom Compounds May Be Useful as a Fungicide

Red imported fire ants are named for the firelike burn of their sting. Now, the same venom that packs such a painful wallop may actually do some good for a change. Studies by scientists at the Agricultural Research Service’s Biological Control of Pests Research Unit in Stoneville, Mississippi, have shown that certain alkaloid compounds in the venom—namely, piperideines and piperidines—can hinder growth of Pythium ultimum, a top crop pathogen worldwide. Chemical controls, delayed plantings, and crop rotation are among methods now used against P. ultimum, which causes damping-off diseases that decay the seed or seedlings of vegetable, horticultural, and cucurbit crops. Despite such measures, damping-off remains a costly problem, and new approaches are needed, notes Xixuan Jin, an ARS microbiologist. He coinvestigated the potential application of fire ant venom in the management of soilborne plant pathogens with ARS entomologist Jian Chen and Shezeng Li of the Institute of Plant Protection in Baoding, China

Antigen recognized by monoclonal antibodies to mesencephalic neural crest and to ciliary ganglion neurons is involved in the high affinity choline uptake mechanism in these cells

High-affinity choline uptake mechanisms are among the characteristics of cholinergic neurons such as the ciliary and choroid subpopulations in the ciliary ganglion (Barald and Berg, 1979). We have produced three monoclonal antibodies (Mabs), two of which were made to 8-day embryonic chick ciliary ganglion (CG) neurons (CG-1, CG-4) (Barald, 1982) and one of which was made to cultured mesencephalic neural crest (NC) cells (CG-14) removed from the embryo 31 hr after incubation. We have shown that all three Mabs label a common 75 kD antigen present on the cell surface of both CG neurons and NC cells (Barald, 1988). Here we report that the CG-1 and CG-4 antibodies, used in the same ratios in which they are synergistically cytotoxic for both the CG and NC cells (Barald, 1988), and Mab CG-14 alone, have specific effects on the high-affinity choline uptake mechanism (HACU) of CG neurons and isolated antigen-positive NC cells in the absence of complement. CG-1 and CG-4 in ratios of 8/1 (the same ratios that are used to kill the CG and the NC subpopulation), but neither singly, inhibit the HACU of CG neurons by 40% and that of isolated antigen-positive NC cells by 75%. However, CG-14 alone, at 1 Μg/ml, inhibits the HACU of both CG neurons and isolated NC cells by 95%. None of the antibodies had an effect on numbers of ouabain binding sites (a measure of the Na + /K + ATPase) or cell surface acetylcholinesterase (AChE) of CG neurons or NC cells isolated by “no-flow” fluorescence cytometry with a Meridian Instruments ACAS470 cytometer. CG or NC cells grown in the presence of the antibodies without complement grow and remain healthy for many weeks. They exhibit no difference in morphology, protein content, lactate dehydrogenase activity (LDH), or division time from untreated sister cultures. Therefore, the antigen recognized by all three Mabs may be involved in a high-affinity choline uptake mechanism, a common characteristic of cholinergic neurons. The Mabs themselves may possibly label some element of the high-affinity transporter or a proximal membrane component. This implies that such a high-affinity uptake mechanism is present in the subpopulation of NC cells at early times in development. If these cells in fact are destined to contribute to the avian CG, these characteristics are present in the subpopulation before the NC cells take on a neuronal morphology.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50220/1/490210205_ftp.pd

Physiological Properties of Cholinergic and Non-Cholinergic Magnocellular Neurons in Acute Slices from Adult Mouse Nucleus Basalis

The basal forebrain is a series of nuclei that provides cholinergic input to much of the forebrain. The most posterior of these nuclei, nucleus basalis, provides cholinergic drive to neocortex and is involved in arousal and attention. The physiological properties of neurons in anterior basal forebrain nuclei, including medial septum, the diagonal band of Broca and substantia innominata, have been described previously. In contrast the physiological properties of neurons in nucleus basalis, the most posterior nucleus of the basal forebrain, are unknown.Here we investigate the physiological properties of neurons in adult mouse nucleus basalis. We obtained cell-attached and whole-cell recordings from magnocellular neurons in slices from P42-54 mice and compared cholinergic and non-cholinergic neurons, distinguished retrospectively by anti-choline acetyltransferase immunocytochemistry. The majority (70-80%) of cholinergic and non-cholinergic neurons were silent at rest. Spontaneously active cholinergic and non-cholinergic neurons exhibited irregular spiking at 3 Hz and at 0.3 to 13.4 Hz, respectively. Cholinergic neurons had smaller, broader action potentials than non-cholinergic neurons (amplitudes 64+/-3.4 and 75+/-2 mV; half widths 0.52+/-0.04 and 0.33+/-0.02 ms). Cholinergic neurons displayed a more pronounced slow after-hyperpolarization than non-cholinergic neurons (13.3+/-2.2 and 3.6+/-0.5 mV) and were unable to spike at high frequencies during tonic current injection (maximum frequencies of approximately 20 Hz and >120 Hz).Our results indicate that neurons in nucleus basalis share similar physiological properties with neurons in anterior regions of the basal forebrain. Furthermore, cholinergic and non-cholinergic neurons in nucleus basalis can be distinguished by their responses to injected current. To our knowledge, this is the first description of the physiological properties of cholinergic and non-cholinergic neurons in the posterior aspects of the basal forebrain complex and the first study of basal forebrain neurons from the mouse

Involvement of Calcium Channels in Depolarization-Evoked Release of Adenosine from Spinal Cord Synaptosomes

The potential involvement of L- and N-type voltage-sensitive calcium (Ca2+) channels and a voltage-independent receptor-operated Ca2+ channel in the release of adenosine from dorsal spinal cord synaptosomes induced by depolarization with K+ and capsaicin was examined. Bay K 8644 (10 nM) augmented release of adenosine in the presence of a partial depolarization with K+ (addition of 6 mM) but not capsaicin (1 and 10 microM). This augmentation was dose dependent from 1 to 10 nM and was followed by inhibition of release from 30 to 100 nM. Nifedipine and nitrendipine inhibited the augmenting effect of Bay K 8644 in a dose-dependent manner, but neither antagonist had any effect on release of adenosine produced by K+ (24 mM) or capsaicin (1 and 10 microM). omega-Conotoxin inhibited K(+)-evoked release of adenosine in a dose-dependent manner but had no effect on capsaicin-evoked release. Ruthenium red blocked capsaicin-induced release of adenosine but had no effect on K(+)-evoked release. Although L-type voltage-sensitive Ca2+ channels can modulate release of adenosine when synaptosomes are partially depolarized with K+, N-type voltage-sensitive Ca2+ channels are primarily involved in K(+)-evoked release of adenosine. Capsaicin-evoked release of adenosine does not involve either L- or N-type Ca2+ channels, but is dependent on a mechanism that is sensitive to ruthenium red

Fungal Foam Tested Against Avocado Threat

Avocados aren’t just nutritional powerhouses; they’re also the chief ingredient in such party favorites as guacamole dip. More than 99 percent of the nation’s $322 million avocado crop is grown in south Florida and southern California (less than 1 percent is produced in Hawaii), which makes recent infestations of groves there by invasive, wood-boring ambrosia beetles so alarming. A host of counter strategies are in the works, including a biobased foam originally developed by Agricultural Research Service scientists for use against Formosan subterranean termites. In Miami-Dade County, Florida, avocado growers are contending with Xyleborus glabratus, the redbay ambrosia beetle. In California, particularly Los Angeles County, the fight is against a different ambrosia beetle species—the polyphagous shot hole borer, Euwallacea sp

Nematode-Filled Capsules Tested Against Corn Rootworms

Each spring, the western corn rootworm (Diabrotica virgifera) awakens from its winter slumber to wreak havoc on corn crops across the United States. The pest emerges in larval form, hatching from small white eggs deposited beneath the soil and causing significant feeding damage to the grain crop’s roots. The toll on U.S. farmers: an estimated $1-2 billion annually in yield losses and chemical control. European growers face a similar threat from the pest, which was first reported in a corn field near the Belgrade international airport in Serbia (formerly Yugoslavia) in 1992, but is presumed to have arrived a decade earlier. Since then, the insect has spread over Eastern Europe and partially over Western Europe. In response, scientists from the United States and Europe have been pooling their expertise and resources to launch a multifaceted counterattack. (See “Rooting Out Rootworm Resistance,” Agricultural Research, September 2010.) On the biological control front, for example, a team of scientists from the Agricultural Research Service and the University of Neuchâtel (UniNE), in Switzerland, is field-testing different formulations to apply beneficial roundworms that prey on the pest. The roundworm, a species of entomopathogenic nematode known as Heterorhabditis bacteriophora, poses no danger to humans, pets, or livestock. But its lethality to rootworms may give corn growers another option for protecting their crops—together with use of insecticides, rotations with non-host crops like soybean, and Bt corn

Multi-Pronged Fight Against Zebra Chip Disease in Potatoes

Thanks to the investigations of scientiststurned- detectives, potato growers in the western United States and abroad now know the identities of the pathogen and insect responsible for outbreaks of the costly tuber disease known as “zebra chip.” So named for the dark stripes it forms inside afflicted tubers when cut and fried to make chips or cooked at high temperatures for other dishes, zebra chip has caused millions of dollars in production and processing losses since its first reported U.S. occurrence in potato fields near McAllen and Pearsall, Texas, in 2000. The disease, whose above-ground symptoms include necrosis and purplish, upward-curling leaves, among others, has since been reported in several other states (California, Nevada, Kansas, Nebraska, New Mexico, Colorado, Wyoming, Washington, Oregon, and Idaho), Mexico, parts of Central America, and New Zealand. Intensive collaborative research by university, industry, and government scientists, including teams from three ARS laboratories—the Yakima Agricultural Research Laboratory (YARL) in Wapato, Washington; the Vegetable and Forage Crops Research Laboratory (VFCRL) in Prosser, Washington; and the Beneficial Insects Research Unit (BIRU) in Weslaco, Texas—narrowed the list of likely suspects to a fastidious (nonculturable) bacterium, Candidatus Liberibacter solanacearum, and the potato psyllid, Bactericera cockerelli, as its insect accomplice or “vector.” (See “Bacterium Identified as Prime Suspect in Zebra Chip Case,” Agricultural Research, October 2009, p. 22.

Trickery and Other Methods Explored To Vanquish Potato Cyst Nematodes

The pale cyst nematode, Globodera pallida, is one bad roundworm. Unchecked, it invades the roots of potato and other host crops to feed, obstructing the free flow of nutrients and causing stunted growth, wilted leaves, and other symptoms that can eventually kill the plant. Severe infestations in potato fields can cause yield losses of up to 80 percent. To make matters worse, female G. pallida nematodes form hard, round cysts that safeguard their eggs from predators and parasites, inhospitable conditions, or a scarcity of food. As many as 30 years may pass before the eggs hatch (cued by a signal from their plant host) to spawn a new generation of nematodes to restart the cycle of destruction. Now, however, a team of ARS and university researchers is working to exploit those plant signals to help counter the emerging threat this pest poses to America’s $3.4 billion tuber crop. The signals are chemicals—called “egg-hatching factors”—secreted from the roots of potato and some other solanaceous plants into the soil. There, “they penetrate the cysts, stimulating the eggs inside to hatch,” explains Roy Navarre, an Agricultural Research Service plant geneticist with the Vegetable and Forage Crops Research Laboratory in Prosser, Washington. The scientists aim to use the chemicals to trick the eggs into hatching when no potato plants are present, leaving the hatchling nematodes with no host and thus no way to survive