EVALUATION OF RESISTANCE OF WINTER-WHEAT TO FUSARIUM-ACUMINATUM BY INOCULATION OF SEEDLING ROOTS WITH SINGLE, GERMINATED MACROCONIDIA

Fusarium acuminatum is one of the causal agents of dryland foot rot of winter wheat in Colorado. The effect of F. acuminatum seedling root i nfection, recorded at heading, on winter wheat cultivars Sandy and CO8 4 was investigated in the greenhouse. Winter wheat seeds were surface disinfested germinated, and vernalized. Vernalized seedling roots were inoculated by placing a single, germinated macroconidium of F. acumin atum on the largest root. inoculated and noninoculated vernalized seed lings were transplanted to pots and half the plants subjected to water stress. inoculated plants had significantly lower survival rates and, at maturity, lower relative leaf water content, fewer tillers, shorte r plant height, and higher cell ion leakage than non-inoculated plants . Wheat cultivars differed significantly for most traits studied. CO84 was susceptible whereas Sandy was more tolerant of the pathogen, part icularly under water stress conditions. These results suggest that rel ative leaf water content, cell ion leakage, and to some extent seedlin g survival may be useful attributes for evaluation of resistance to th e root rot pathogen.