RELATIONSHIPS BETWEEN PITH CELL CONDITION AS ASSESSED BY TETRAZOLIUM CHLORIDE AND INCIDENCE OF GIBBERELLA STALK ROT IN CORN

The response of pith tissue to tetrazolium chloride was used to assess the physiological condition of pith cells of the basal internodes of stalk-rot-resistant and susceptible inbred corn plants during ear development. Although no consistent differences in pith tissue response between the inbreds could be detected 1–2 weeks before mid-silk, differences in cell condition in the basal pith became apparent during ear development, possibly because this imposed a stress on the plant. Measurements of cell condition made 1–3 weeks after mid-silk could be associated with about half of the observed variation in final stalk rot, and the results of a third test made 0–10 days before ear maturity could be associated with most of the variation in stalk rot. Plant size in relation to kernel yield accounted for part only of the differences in pith cell condition and stalk rot incidence.