Why do vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants?

Vegetatively propagated plants are genetically identical to the parent plant and to all the other plants produced from them. Such plants are referred to as clones. Since all these plants have the same genetic makeup, they also share the same strengths and weaknesses, including susceptibility to diseases caused by fungi, bacteria, or viruses. If a disease-causing organism can infect one plant, it can easily infect the entire cloned population because none of the plants possess genetic variations that might provide resistance against the said disease. As a result, a single disease can spread rapidly and destroy the whole crop.

This situation is different in sexually reproduced plants. During sexual reproduction, genetic recombination and the fusion of gametes from two parents create variations among the offspring. Due to these genetic variations, some plants may develop resistance to a particular disease and survive even if others are affected. Therefore, the lack of genetic variation in vegetatively propagated plants makes them more vulnerable to diseases.