A comparative study of pith cell death in stalk internodes of corn grown on organic and conventional fields

A few farmers in the Midwest produce corn (Zea mays L.) commercially by using organic methods, i.e., use no synthetic fertilizers or pesticides. Studies have been conducted previously on organic vs. conventional fields to compare yield, soil properties, stalk lodging and rot, and crude protein. However, pith cell death in stalk internodes, an important trait related to stalk lodging and stalk rot, has not been studied previously under organic and conventional management systems. Fertility differences exist between organically-managed and conventionally-managed fields which can influence pith cell death and related traits. This study was conducted to compare pith cell death in corn stalks on matched pairs of organic and conventional fields (2 in Illinois, 2 in Iowa, and 1 in Minnesota). For the four lowermost consecutive internodes above the brace roots examined in this study, there was no consistent pattern for pith cell death differences among pairs. In three of five pairs, the second internode pith cell death was higher on organic fields than on conventional fields. The same pattern was observed for the third stalk internode. Numbers of European corn borer (Ostrinia nubilalis Hübner) were less in the stalks on organic plots, a plausible cause for greater stalk lodging and rot resistance on organically-managed fields. Further study of pith cell death and stalk rot relationship under organic and conventional managements is needed to elucidate fertility relations and other unique factors at work on organic and conventional fields. It appears that while there are some factors that affect pith cell death, stalk rot, and stalk lodging similarly, there may be other factors that affect these three traits differentially.

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.