Use of uniconazole to control plant height for an industrial/pharmaceutical maize platform

A variety of crops and their production systems have been proposed as platforms for plant-made pharmaceuticals (PMPs) and plant-made industrial compounds (PMICs), each with their own advantages and challenges. Maize grown in isolated, confined environments avoids several challenging issues associated with future production of PMPs/PMICs. When grown under optimizing conditions of temperature, nutrition, and water status, however, maize tends to elongate excessively, which contributes to lodging and interferes with delivery of sufficient overhead electric lighting to the inner foliar canopy where ears develop. Suppression of extensive stem elongation without compromising grain yield would help in delivering overhead light into the foliar canopy for efficient grain production. The plant-growth retardant uniconazole (UCZ) was tested for its effects on maize height and grain yield. UCZ reduced plant height effectively, but dosages that strongly suppressed stem elongation also decreased grain yield, ear length, and cob weight. Duration of growth suppression was prolonged at high UCZ concentrations. UCZ also induced branching of maize, which was enhanced as concentrations increased. A range of ear types occurred on branches, with some conversion of ears to tassels at high UCZ concentrations. Minimum stem diameter declined with increasing UCZ concentration. Plant height was reduced from 306 cm to 232 cm (−25%) using a concentration of 1.0 mg/L UCZ without affecting grain yield of 180–200 g per plant. This low UCZ concentration caused 1–2 basal branches to form that would not affect planting density in a cropping situation.

Research highlights
► Height control of maize in controlled environments is feasible with UCZ.
► 0.5 or 1.0 mg/L UCZ suppressed final height without reducing grain yield.
► Total grain yield decreases above 1.0 mg/L UCZ.
► UCZ induces branching and modifies ear morphology in maize.