The following inbreds and single crosses were grown in replicated plots
in the field and scored visually at tassel emergence for reaction to aphids:
| C131A | OH43 | B14 | Bx x C131A |
| B37 | C103 | Bx Bx | B37 x WF9 |
| B49 | WF9 | bx bx | N28 x B37 |
They were evaluated following natural infestation on the basis of 1 = no infestation to 4 = heavily infested. Hydroxamate concentration was determined by use of the rapid procedure (Crop Sci. 14:601-603, 1974). A significant correlation (r = 0.58) was obtained between hydroxamate concentration and aphid resistance. These results agree with our previous work (Crop Sci. 7:55-58, 1977).
Recent work with the rapid procedure seems to indicate that the concentration of FeCl3 used previously (0.1N) may not be sufficient to react with all the hydroxamic acids in high DIMBOA lines. We are currently testing the effects of different concentrations of FeCl3 (0.1N, 0.3N and 0.5N) on the colorimetric reaction. It also appears that anthocyanin pigments which often develop at the base of the stem of corn seedlings may be greatly reduced by wrapping the basal stem in aluminum foil. These pigments may interfere with the colorimetric reaction.
G. M. Dunn, D. G. Routley and David Beck
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