When invading a plant what is the first obstacle that plant pathogens must overcome?

The first obstacle that pathogen must first overcome is the physical barriers on the exterior of a plant such as substances that contained protoplast of the plant cells, waxy cuticle or the outer epidermal layer such as bark or thorn. Some pathogens uses the wounds of the plant that was made by an animal or through the stomates and lenticels of a plant to penetrate and damage the plant.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."