Also “resistance” is a general term. There are degrees of resistance to consider, like single race resistance or more broad spectrum resistance, and then the concept of total immunity to all races of PM… is this actually possible in roses like Baby Love??
There is no doubt in my mind, that an invisible colonization of PM turns into a visible infection we can see with our eyes, when the interplay of host(genes, immune system) and pathogen (race type, dose/concentration of infecting agent-environemntal factors) is just optimal for that to occur.