The majority of plants exhibit resistance to a wide range of pathogens. Even microorganisms that wreak havoc on specific plant species often fail to colonize others. This intriguing observation prompts the question, how do plants naturally develop enduring resistance against pathogens? The phenomenon where all members of a species exhibit resistance to all variants of a specific pathogen is termed non-host resistance. While the fundamental principles of the plant immune system have been uncovered recently, the genetic and molecular mechanisms underpinning non-host resistance remain largely elusive. Our research aims to investigate why the citrus pathogen Xanthomonas citri pv. citri is incapable of infecting a selection of evolutionarily distant non-host plants. This exploration will shed light on the diverse mechanisms plants employ to restrict non-adapted pathogens. The findings from this research could potentially unveil factors that dictate host specialization in pathogenic bacteria.