Chemical correlates of constitutive and inducible resistance against Spodoptera frugiperda in four varieties of soybeans

Soybean varieties differing in constitutive and inducible resistance were used to measure the activity of lipoxygenases, peroxidase, phenylalanine ammonia lyase, proteinase inhibitor, total pheonics and a flavonoid compound, diadzein.  Plants at 3-4 leaf stage were used for feeding damage by S. frugiperda larvae on a leaflet of a fully opened trifoliate leaf at the terminal node. Leaf disk bioassays were conducted on the third instar FAW larva by using a leaflet from damaged and undamaged plants to assess constitutive and induced resistance, respectively. To correlate results of larval bioassays with those from biochemical assays, biochemical assays were performed by using a leaflet of the same trifoliate leaf used for larval bioassays.