ABSTRACT
Under controlled conditions in a BOD chamber, eight lines of green leaf lettuce and the cultivar Solaris were evaluated by means of a latency index (IL) as a measure of downy mildew severity, while the resistance response was assessed based on the percentage of seedlings with sporangia (PE) when inoculated with nine races of Bremia lactucae alone and with one single mixture of all races. The IL and PE for the lines were inferior to those shown for the cultivar Solaris, used as the susceptibility standard. The lines L1, L2, L3 and L4 were highly resistant when inoculated (PE = 0.0%) with the nine races/mixture; the lines L5, L6, L7 and L8, depending on the inoculated race/mixture, showed high resistance level (PE = 0-4.6%) and incomplete resistance (PE = 6.0-15.1%), and the line L5 presented a heterogeneous resistance and susceptibility reaction to race SPBl:07 (PE = 27.9%).
Keywords
sporangia; Lactuca sativa; downy mildew