How does natural selection affect plants in a bulk breeding population?

In the bulk-population method of plant breeding, natural selection acts as a filter during the period of bulk propagation. Because the population is grown in large plots under conditions that simulate commercial practice, natural selection tends to eliminate plants that possess poor survival value within that specific environment.1

While the breeder manages the population in mass without keeping individual ancestry records, this natural pressure helps refine the population by favoring individuals better suited to survive and reproduce in the field. This process is distinct from artificial selection, which the breeder may simultaneously apply—such as destroying plants with undesirable major genes or using specific harvesting techniques to select for traits like early maturity or increased seed size.1

Ultimately, the bulk-population method leverages natural selection to reduce the frequency of less fit genotypes, allowing the breeder to handle large numbers of individuals inexpensively before making final single-plant selections for evaluation.1