IMAGE-ANALYSIS AND VISUAL ESTIMATES FOR EVALUATING DISEASE REACTIONS OF CORN TO FUSARIUM STALK ROT

Two field-grown hybrids were evaluated in three tests (1987-1989) for reaction to the stalk rot fungi Fusarium moniliforme, F. graminearum, and F. proliferatum, using a visual rating scale (0-4) and image analy sis (0-100%). Both rating methods indicated that hybrid W153R X A619 h ad more stalk discoloration than A632 X A619 when inoculated with any of the three Fusarium species. The difference between hybrids was grea ter when an image analyzer was used. Significant differences (P = 0.05 ) between the disease reactions caused by the three pathogens were fou nd among ratings made with the image analyzer in all 3 yr of testing, F. moniliforme, compared with the other Fusarium spp., caused signific antly more (P 0.05) stalk discoloration in the 1987 and 1988 tests whe n measured by the image analyzer. Significant differences among discol oration caused by Fusarium species were found only in the 1988 test us ing the visual rating scale. The image analyzer provides a more precis e means of evaluating corn for susceptibility to Fusarium stalk rot as compared to visual ratings.