Effect of L-3,4-dihydroxyphenylalanine, ornithine and gamma-aminobutyric acid on winter wheat resistance to grain aphid

The association between the concentrations of L-3,4-dihydroxyphenylalanine (L-DOPA), ornithine, and gamma-aminobutyric acid (GABA) in winter wheat cul tivars with their antibiotic resistance to the grain aphid Sitobion avenae (F.) (Hom., Aphididae) was studied. The antibiosis was measured under field conditions using the intrinsic rate of natural increase (r(m)). The conten t of the studied non-protein amino acids was estimated in flag leaf at the beginning of anthesis growth stage. Highly significant negative correlation s were found between the r(m) values and concentrations of L-DOPA (r = -0.9 37) and ornithine (r = -0.907), but not with GABA (r = -0.363). The contrib ution of these allelochemicals to the resistance of the plants to insects i s discussed.