Answer:
lack of genetic diversity in the potato plants
Step-by-step explanation:
The great famine that hit Ireland in the 19th century came about because a plague hit potato plantations across the country. The potato was the main source of food for the Irish population, at that time, when the pest hit the plantations, almost all of the country's crops were consumed and the population had to face serious problems.
A crucial point for the pest to attack all potato crops in the country was the existence of monoculture that influenced the lack of genetic diversity in the potato. As the Irish always planted the same species of potato, it was almost impossible for any plant to be resistant to the pest, which managed to consume everything with ease.