Identification by LC/ESI/MS/MS and LC/DAD of flavonol and isoflavonoid glycosides modulated by solar UV-B radiation and herbivory in soybean leaves at field: effects on Anticarsia gemmatalis larvae.

DILLON, F; CHLUDIL, H; ZAVALA, J. A.

Bogota

Congreso; III Congress of the Latin American Association of Chemical Ecology (ALAEQ); 2014

Latin American Association of Chemical Ecology (ALAEQ)

Solar ultraviolet B (UV-B) radiation has been largely reported to enhance plant defenses against insects, but it is unclear what traits define insect resistance at field in crop systems such as soybean. Here we study the effects of solar ultraviolet B (UV-B) radiation on: a) the modulation of phenolic compounds and trypsin inhibitors (TPI) in soybean leaves b) survival and mass gain of Anticarsia gemmatalis larvae in field conditions.   Cultivar (cv.) Williams and cv. Charata were planted at field under two treatments generated by thick plastics: ambient UV-B and attenuated UV-B. Neonates of A. gemmatalis larvae were placed in transparent tull bags on the last fully expanded soybean leaves and the number of surviving larvae was recorded daily and at day six weighted. Flavonoids glycosides from soybean leaves were identified by HPLC-DAD and HPLC-ESI(+)-Q-TOF   Exclusion of UV-B radiation increased mass gain of larvae fed on cv. Charata, however this changes were not that important in cv. Williams. TPI activity, genistin, malonyl genistin and a benzoic acid derivate were induced by A. gemmatalis damage in both cultivars, but only in cv. Williams this induction was more intense in plants that grown under solar UV-B radiation. TPI activity and genistein derivatives didn´t explain the differences found in survivorship and mass gain of larvae that fed on cv. Charata in the two UV-B treatments. However, after identification and quantification of flavonols present in soybean leaves (tri and diglycosides of quercetin, isorhamnetin and kaempferol) we found an association between modulation of plant resistance to herbivory and two quercetin triglycosides present only in cv.Charata.   We found that modulation of two quercetin triglycosides were more important in defining larvae performance than the modulation of other typical defenses such as TPI activity and genistin. We also identified a benzoic derivate which was induced by herbivory independently of UV-B radiation.