Analysis of elicitors in different varieties of corn silk

Abstract

Plant response to insect damage offers an environmentally sound alternative to pesticides. In this context, a work was conducted in the molecular characterization of different corn silk varieties, to obtain an additional information to a protection study of tomato plant against devastating insect (Helicoverpa zea). Indeed, corn silks transmit volatile compounds that attract H. zea and its natural enemies. Once H. zea installed, the produced flavonoids-C-glycosylated reduce larvae growth. Five corn varieties (Java; Garrison; Sugar Jean; Nova; Golden Bantam) were studied by solid phase micro extraction gas chromatography mass spectrometry (SPME-GC/MS) and liquid chromatography with mass spectrometry multiple reaction monitoring (LC/MS-MRM). Thirty-eight volatile molecules were identified by SPME-GC/MS. These molecules have been quantified by external calibration from four standards (hexenyl acetate, phenyl ethanol, phenyl acetaldehyde, methyljasmonate) of the same families. The concentration of these volatile compounds was low in Sugar Jean variety while the Garrison and Golden Bantam variety exhibited higher concentration in volatiles such as phenylacetaldehyde. In LC/MS-MRM, the study of molecule fragmentation showed unit losses of 60, 90, 120 Da and that of 132, 146, 162 Da, which allowed to distinguish between C- and O-glycosylated flavonoids. Flavone C-glycosides were identified in each silk, such as maysin and apimaysin. Some molecules were present in various amounts in the studied varieties. The relative content of maysin and ax-5”-methane-3'-methoxymaysin was higher in Java variety, while the relative content of apimaysin and eq-4”-OH-maysin were more prevalent in Golden Bantam variety, and that of luteolin O-glucoside was more important in Sugar Jean variety. These two chromatographic techniques allowed differentiating between varieties of corn silk thanks to their chromatographic fingerprint. (Texte integral)