The correct options are
A The genetic constitution of the plant
B Resistance genes present in the plant
Plants are innately immune to a vast majority of bacterial and fungal pathogens. This disease resistance is basically determined by the genetic constitution of the plant. It is conferred by multiple, diverse R genes or resistance genes present in the plant. The R genes confer resistance naturally by various means. Some code for toxins that kill pathogens and some code for antimicrobial proteins.