Quantitative assessment of kernel set and risk of out-crossing in maize based on flowering dynamics
Pollination in maize can occur only if airborne pollen shed by the staminate flowers on the tassel is captured by the stigmas of the pistillate flowers borne on the ear. Since maize domestication, and especially with the introduction of hybrid seed production, many attempts have been made to control pollination to ensure maximum kernel set and high levels of genetic purity. The central hypothesis of this dissertation is that pollen shed and silk emergence are predictable processes, which can be simply quantified and used to characterize the capacity of the male inbreds to produce pollen and the ability of the females to extrude silks. This information coupled with an assessment of pollen viability, could be used to model kernel set under varying conditions and to predict pollen drift and the risk of genetic contamination from one field to another. Chapter 2 presents a novel method to quantify the timing and intensity of pollen shed using passive pollen traps and capitalizing on the capacity of pollen to fluoresce. Chapter 3 provides another novel method of relating genetic differences in pollen production to the morphological characteristics of plant tassels. Chapter 4 describes a mathematical model developed to simulate potential kernel set from seasonal dynamics of pollen shed and silk exsertion. Chapter 5 successfully applies the model to hybrid seed production fields and demonstrates its utility to define management strategies that would optimize seed production. Chapter 6 presents an indirect approach to assess loss of pollen viability during its transport in air. Quantitative relations between environmental conditions during pollen dispersal (i.e. temperature, relative humidity) and pollen desiccation that can be used to assess pollen viability are shown. Finally, chapter 7 presents a quantitative approach to assess out-crossing and self-pollination risks based exclusively on the flowering characteristics of a given field.