PUTATIVE ROLE OF PHOTODIMERIZED PHENOLIC-ACIDS IN MAIZE RESISTANCE TOOSTRINIA-NUBILALIS (LEPIDOPTERA, PYRALIDAE)

Five genotypes of maize were grown under three light regimes in the fi eld. Artificial infestation with European corn borer, Ostrinia nubilal is (Hubner), egg masses resulted in greater leaf feeding damage for pl ants grown under a UV absorbing plastic (UV-) than for the same genoty pes grown under UV transmitting (UV+) plastic or in the open. Leaf bio assays performed on tissue from the three different light regimes show ed similar trends. Foliar nitrogen content was reduced as much as 15% for UV- plants. 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one levels were consistently higher in UV- plants as were the levels of cell-wal l-bound hydroxycinnamic acids (HCA). Light-activated dimers of HCA cal led truxillic and truxinic acids were lower in UV- plants. These resul ts indicate that cell-wall-bound truxillic and truxinic acids are an a dditional resistance mechanism that provide an explanation for increas ed susceptibility of greenhouse grown plants to folivores.