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Genistein and naringenin, plant phenolic compounds, are recognized for their health benefits and role in plant defense against herbivores. However, little research exists on how these compounds affect aphid feeding, particularly that of the black bean aphid (Aphis fabae Scopoli) (Hemiptera: Aphididae), a major pest. This study aimed to evaluate the effects of genistein and naringenin, applied in vitro at different concentrations, on the feeding behavior of A. fabae. Statistical analysis indicated that both the type and concentration of flavonoids significantly influenced aphid stylet activity, salivation, and ingestion. Higher concentrations of both compounds hindered feeding behavior. A longer initial probe was observed on gels containing the studied flavonoids. Genistein at 0.1% completely inhibited salivation while at 0.01%, it reduced the duration of salivation activities. Both compounds also delayed the start and lengthened the duration of active ingestion, though A. fabae tolerated genistein better than naringenin. Naringenin's effects on feeding behavior were more pronounced at higher concentrations. These findings suggest that genistein and naringenin could be valuable chemicals to protect plants from aphids in a sustainable and environmentally friendly way. [ABSTRACT FROM AUTHOR]

The aim of the present study was to compare ascorbate (ASA) content and ascorbate peroxidase (APX) activity in seedlings of the less susceptible triticale cultivar Witon and the more susceptible triticale cultivar Tornado after infestation by the grain aphid Sitobion avenae (F). and the bird cherry-oat aphid Rhopalosiphum padi (L.). The content of ASA in triticale seedlings slightly decreased after 24 hrs of infestation by cereal aphids, but prolonged feeding (48 hrs and 72 hrs) resulted in significant losses in ASA dependent on cultivar and aphid species. The aphid infestation caused an increase in APX activity in triticale tissues throughout the test period. The aphid herbivores induced APX activity to a higher level in a less susceptible cultivar than in a more susceptible one. The oligophagous species R. padi caused a higher decrease of ASA and stronger induction of APX activity in tested triticale than the monophagous species S. avenae. The experiments carried out indicate that ascorbate and ascorbate peroxidase may play a significant role in the defense mechanism of aphid infested triticale. [ABSTRACT FROM AUTHOR]

Flavonoids play an important role in interactions of plants with the environment. Liquid chromatography (HPLC) was used to determine the flavonoid profiles (especially luteolin, tricin, and chrysoeriol glycosides), their total concentrations, and changes in the amounts of eight flavones found in the aerial parts of alfalfa (Medicago sativa L.) (Fabaceae) Radius cv., uninfested and infested by the pea aphid (Acyrthosiphon pisum Harris) (Homoptera: Aphididae). It was shown that both control and infested green aerial parts of alfalfa plants had similar flavonoid profiles. The dominant flavonoid of alfalfa was compound 7-O-[2-O-feruloyl-ß-D-glucuronopyranosyl(1→2)-O-ß-D-glucuronopyranosyl]-4'-O-ß-D-glucuronopyranosideluteolin. Compound 7-O-{2'-O-feruloyl-[ß-D-glucuronopyranosyl(1→3)]-O-ß-D- glucuronopyranosyl(1→2)-O-ß-D-glucuronopyranosidetricin was present in the smallest amounts. The total concentration of flavones was rather high and ranged from 11.13 to 12.34 mg/g d.m., but there were no significant differences between uninfested and infested alfalfa plants. There was a correlation between the concentration of flavonoid glycosides in the alfalfa plants and pea aphid abundance. Pea aphid daily fecundity per female was affected by luteolin, tricin, and chrysoeriol glycosides and the level of chrysoeriol glycosides affected ingestion of xylem sap by the aphid. This finding may indicate that the studied flavonoid glycoside forms are biologically active in alfalfa -- A. pisum interactions. [ABSTRACT FROM AUTHOR]