Identification of Differential Volatiles in Resistant/Susceptible Faba Bean and Aphis craccivora 's Behavioral Responses to These Volatiles.

Aphis craccivora is a major piercing-sucking pest that causes severe yield and quality losses in Vicia faba. Here, two faba bean lines with extreme aphid resistance (K, resistant; G, susceptible) were subjected to aphid-infested and uninfested treatments. Constitutive and induced volatile organic compounds (VOCs) were identified by SPME-GC-MS, and Aphis craccivora's behavioral responses to VOCs were assayed via four-arm olfactometer. ROAV and multivariate statistical analysis were used to explore the correlation between VOC profiles and aphid resistance. Results showed K had marginally more VOCs (344 ~ 345) than G (339), with a conserved core VOC library but distinct unique metabolites and category contribution ratios between the two lines. 2-methoxy-3-(2-methylpropyl) pyrazine (highest ROAV in G) and (E, Z)-2,6-nonadienal (core aroma compound in K) were the key differential VOCs. K exhibited predominant upregulation of differential metabolites after aphid infestation, and constitutive green/sweet aroma VOCs differed significantly between K and G. Behavioral assays identified 10 VOCs repellent and 4 VOCs attractive to Aphis craccivora, among which Methyl salicylate exhibited consistent repellency across all tested concentrations only eucalyptol showed concentration-dependent behavioral effects. This study elucidates the chemical ecological mechanism of faba bean mediating Aphis craccivora host selection via regulated specific VOC emission, confirming the critical roles of both constitutive and induced VOCs in aphid resistance. The findings provide a theoretical basis for aphid-resistant faba bean molecular marker-assisted breeding, plant-derived pesticide development, and Aphis craccivora ecological regulation.