Comparison of DIMBOA concentrations among wheat isolines and correspondingplant introduction lines

The concentration of a hydroxamic acid, also known as DIMBOA (2,4-dihydroxy -7-methoxy-1, 4-benzoxazin-3-one), in 6-d old wheat seedlings was examined using reverse-phase high performance liquid chromatography (HPLC). Wheat pl ant introduction (PI) lines PI 137739 (Dn1 gene), PI 262660 (Dn2 gene), and PI 294994 (Dn5 gene), the corresponding near-isogenic lines`Betta'-Dn1, Be tta-Dn2 and Betta-Dn5, and susceptible Betta wheat were used in the study. The Dn2 gene conferring Russian wheat aphid, Diuraphis noxia (Mordvilko) (H emiptera: Aphididae), tolerance was not related to DIMBOA concentration in wheat. Of the lines with Dn1 and Dn5 genes that confer antibiosis to D. nox ia, only lines with the Dn5 gene showed increased DIMBOA accumulation. Howe ver, the Dn5 and the DIMBOA biosynthesis genes are not located in the same chromosome group. Possible relationship between the Dn5 gene and DIMBOA acc umulation was discussed. This study indicates that DIMBOA concentration doe s not completely explain D. noxia resistance in the wheat lines examined an d a comprehensive examination of other allelochemicals (e.g., phenolics) is necessary.