Final answer:
The term describing genetic homogeneity leading to susceptibility to large-scale issues in plants is 'genetic vulnerability'. It is exacerbated by genetic drift and practices like monoculture that reduce biodiversity.
Step-by-step explanation:
The term used to indicate the genetic homogeneity and uniformity of a group of plants that predisposes it to susceptibility to pests, pathogens, or environmental hazards of large-scale proportions is genetic vulnerability. When a population is genetically homogeneous, it lacks genetic variation, which means that a single pest or disease outbreak can have devastating effects. This was famously exemplified by the Irish Potato Famine in the 1840s when the potato crops in Ireland, being genetically similar, were all susceptible to a potato blight, leading to a catastrophic famine.
Genetic drift, including the bottleneck effect, can contribute to genetic vulnerability by significantly reducing the genetic variation within a population following a disaster that kills a large portion of that population at random. Similarly, practices like monoculture in agriculture, leading to drastic reductions in biodiversity, amplify this vulnerability because they promote genetic uniformity.