ABSTRACT
During the plant cultivar–bacterial pathogen interaction, in a favorable environmental condition for disease development, if the plant host cv shows no reaction or hypersensitive reaction without the induction of disease symptoms, this type of reaction is known as plant resistance to the given pathogen. The concept of using single race to determine horizontal resistance is based on the use of a more virulent race capable of attacking most of the resistant genes in a plant cv. Development of either hypersensitive browning reaction with no further spread or no reaction indicate the presence of vertical resistance in the crop cultivar against the specific race/isolate of the bacteria. Record the hypersensitive reaction or water-soaking reaction of individual races on the same plant. If the plant shows resistance to move than one or several races, it is presume to possess horizontal resistance against the described races.
