Kenneth C. Jones

Bio: Kenneth C. Jones is an academic researcher from United States Department of Agriculture. The author has contributed to research in topics: Aphid & Acyrthosiphon pisum. The author has an hindex of 8, co-authored 10 publications receiving 539 citations. Previous affiliations of Kenneth C. Jones include University of Utah.

Feeding deterrency of some pyrrolizidine, indolizidine, and quinolizidine alkaloids towards pea aphid (Acyrthosiphon pisum) and evidence for phloem transport of indolizidine alkaloid swainsonine

Abstract: The feeding deterrency of a series of pyrrolizidine, indolizidine, and quinolizidine alkaloids and selected derivatives was measured against the pea aphid (Acyrthosiphon pisum Harris). The indolizidine alkaloid, castanospermine, was intensely active (ED50, 20 ppm) as were the quinolizidine alkaloids, but only modest feeding deterrency was observed with most of the pyrrolizidine alkaloids tested. The insect survival rate of aphids on a castanospermine-supplemented diet over 24 hr was also very low relative to the controls. Castanospermine does not inhibit aphid trehalase. The indolizidine alkaloid swainsonine occurred in the honeydew of pea aphid feeding on the locoweed,Astragalus lentiginosus. Since the pea aphid is a phloem feeder, swainsonine must be transported in the phloem.

Probing behavior of the greenbug (schizaphis graminum, biotype c) on resistant and susceptible varieties of sorghum

Abstract: The probing behavior of biotype C of the greenbug, Schizaphis graminum (Rondani) on susceptible and resistant lines of sorghum, Sorghum bicolor (L.) Moench., was electronically monitored. Waveforms corresponding to salivation, phloem ingestion and non-phloem ingestion are described. The results of a parallel study revealed that the rate of population growth of S. graminum was significantly greater on susceptible lines of sorghum [i.e., NC + 70X. SC423 (Purple). SC423 (Tan)] than on resistant lines (i.e., TAM 2567, IS 809). Aphids probing the resistant lines of sorghum showed a significantly reduced imbibition of phloem sap compared with those aphids which fed on susceptible varieties. Also, increased numbers of separate probes and increased duration of non-probing were associated with greenbugs feeding on resistant lines. Greenbugs monitored on the nonhost plant, rice, exhibited non-phloem ingestion, but not phloem ingestion. Resistance in sorghum to greenbugs is associated with the phloem. There appear to be no physial differences between the sorghum varieties in the location of or extent of lignification around the vascular bundles. Hence, resistance probably involves plant natural products associated with the phloem sap. ZUSAMMENFASSUNG Probeverhalten von Schizaphis graminum, Biotyp c an resistenten und anfalligen Sorghumsorten Das Probeverhalten des Biotyps C von Schizaphis graminum (Rondani) an anfalligen und resistenten Klonen von Sorghum Sorghum bicolor (L.) Moench., wurde elektronisch registriert. Wellenfiguren fur den Speichelfluss, die Phloemaufnahme und − nichtaufnahme werden beschrieben. Die Ergebnisse eines Parallelexperiments zeigten, dass die Zuwachsrate von S. graminum bedeutend grosser war an anfalligen Klonen [NC + 70X, SC423 (Purpur), SC423 (Beige)] als an resistenten Klonen (TAM 2567, IS 809). Blattlause an resistenten Klonen saugten wahrend bedeutend kurzerer Zeit Phloemsaft als Blattlause an anfalligen Klonen. Ferner ergab sich eine grossere Zahl Probestiche und eine langere Dauer des Nichtprobens. Blattlause, welche an der Nichtwirtspflanze Reis beobachtet wurden, nahmen Nichtphloemsubstanz aber keinen Phloemsaft auf. Resistenz von Sorghum gegen Sch. graminum steht in Zusammenhang mit dem Phloem. Offenbar gibt es keine physikalischen Unterschiede zwischen den Sorghumklonen in Bezug auf die Verteilung und die Verholzung der Gefassbundel. Daher muss die Resistenz wahrscheinlich mit Inhaltsstoffen des Phloemsafts zusammenhangen.

Aphid feeding deterrents in sorghum : Bioassay isolation and characterization.

Abstract: Improvements in a synthetic diet for use in a bioassay to screen for feeding deterrents againstSchizaphis graminum, greenbug, are reported. Feeding on the synthetic diet was highly pH dependent with maximum feeding occurring at about pH 8.0. The bioassay was used as a guide in the isolation of feeding deterrent substances from aphid-resistant lines of sorghum (Sorghum bicolor). The major greenbug feeding deterrents isolated from sorghum leaves wereP-hydroxybenzaldehyde (ED50 0.13%), dhurrin (ED50 0.16%), and procyanidin (ED50 0.08%).

Cultural Practice and Environmental Impacts on the Flavonoid Composition of Grapes and Wine: A Review of Recent Research

Abstract: Flavonoids are a large and diverse group of compounds that, by their presence or absence, contribute greatly to wine quality. While the flavonoid content and composition of a wine reflects the vinification process to some extent, the primary determinant is the composition of the grapes at harvest. Thus, considerable research has been directed toward understanding the nature of flavonoids in grapevines, the factors that influence their biosynthesis, and how this knowledge might be used to manage and manipulate the flavonoid composition of berries at harvest. This review examines the flavonoids as a class of compounds, the role these compounds play in the plant, their contributions to wine quality, and recent research on the impacts of environmental factors and cultural practices on the flavonoid content and composition of grape berries.

Phenolics in ecological interactions: The importance of oxidation.

Abstract: The ecological activities of plant phenolics are diverse and highly variable. Although some variation is attributable to differences in concentration, structure, and evolutionary history of association with target organisms, much of it is unexplained, making it difficult to predict when and where phenolics will be active. I suggest that our understanding is limited by a failure to appreciate the importance of oxidative activation and the conditions that influence it. I summarize examples of oxidative activation of phenolics in ecological interactions, and argue that physicochemical conditions of the environment that control phenolic oxidation generate variation in ecological activity. Finally, I suggest that measurements of oxidative conditions can improve our predictions of phenolic activity and that experiments must be designed with conditions appropriate to the biochemical mode of phenolic action.

Plant breeding: importance of plant secondary metabolites for protection against pathogens and herbivores

Abstract: Chemical protection plays a decisive role in the resistance of plants against pathogens and herbivores. The so-called secondary metabolites, which are a characteristic feature of plants, are especially important and can protect plants against a wide variety of microorganisms (viruses, bacteria, fungi) and herbivores (arthropods, vertebrates). As is the situation with all defense systems of plants and animals, a few specialized pathogens have evolved in plants and have overcome the chemical defense barrier. Furthermore, they are often attracted by a given plant toxin. During domestication of our crop and food plants secondary metabolites have sometimes been eliminated. Taking lupins as an example, it is illustrated that quinolizidine alkaloids are important as chemical defense compounds and that the alkaloid-free varieties (“sweet lupins”), which have been selected by plant breeders, are highly susceptible to a wide range of herbivores to which the alkaloid-rich wild types were resistant. The potential of secondary metabolites for plant breeding and agriculture is discussed.

The Chemical Ecology of Aphids

Abstract: Insects are sensitive to chemical aspects of their environment, particularly with regard to host and mate location. Aphids can select individual or a few closely related host plant species from a wide range of nonhost vegetation (65, 71). This selection relies upon the detection of secondary plant compounds as well as primary metabolites associated with the physiological condition of the host plant (82). Use of long-range volatile chemical cues in aphid-plant and aphid-aphid interactions was formerly considered unlikely (78, 108). Never­ theless, recent work reviewed here demonstrates that olfaction plays a more extensive role in the chemical ecology of aphids than previously thought. Thc study of aphid chemical ecology involving volatile semiochemicals, particularly pheromones, has been greatly enhanced by the development of electrophysiological rccordings from aphid antennae, using the electroan­ tennograph (EAG) and single-cell recording (SCR) methods. SCR directly coupled to high-resolution capillary column gas chromatography (GC-SCR) provides a powerful tool for locating the active components in behaviorally active samples (154). Analysis by other highly sensitive techniques such as

Dietary tannins and salivary proline-rich proteins: interactions, induction, and defense mechanisms.

Abstract: INTRODUCTION 424 TANNINS 424 Chemistry 425 Condensed Tannins ....... . ..... ... ... 426 Hydrolyzable -Tannins ... 426 Assays 426 Biological Roles and Dietary Ef ects 428 Interactions of Tannins and Proteins 430 PROLINE-RICH PROTEINS 432 Background 432 Molecular Biology 433 Functional Aspects 433 SUMMARY AND FUTURE CONSIDERATIONS 435