Figure 4.

Growth of Pathogen in the sfd Mutants.

(A) Bacterial numbers in the sfd mutants. Psm (OD₆₀₀ = 0.0002) was infiltrated into the abaxial surfaces of leaves of wild-type (WT), npr1, ssi2, ssi2 npr1, sfd1-1 ssi2 npr1, sfd1-2 ssi2 npr1, sfd2-1 ssi2 npr1, sfd2-2 ssi2 npr1, sfd2-3 ssi2 npr1, and sfd4 ssi2 npr1 plants with a needleless syringe. Leaf discs were harvested from the inoculated leaves at 3 days after inoculation, weighed, and ground in 10 mM MgCl₂, and the bacterial numbers were titered. Each sample contained five leaf discs. The bacterial numbers, presented as colony-forming units (CFU) per mg of leaf tissue, represent the average of five samples ± sd.

(B) B. cinerea disease ratings in the sfd mutants. Leaves of 4-week-old soil-grown wild-type, npr1, ssi2, ssi2 npr1, sfd1-1 ssi2 npr1, sfd1-2 ssi2 npr1, sfd2-1 ssi2 npr1, sfd2-2 ssi2 npr1, and sfd4 ssi2 npr1 plants were inoculated with spores of B. cinerea. Four days later, plants were scored for the extent of spreading necrosis. Leaves from each line were grouped based on the extent of necrosis. A four-step grading system was used. Leaves with <25%, 25 to 50%, 50 to 75%, and 75 to 100% of leaf area exhibiting necrosis were given scores of 0.25, 0.5, 0.75, and 1, respectively. The leaves in each category were counted, multiplied by the score, and divided by the total number of leaves inoculated (given next to each bar) to give an infection rating for each line. The “relative infection rating” for each line was calculated as the ratio of the infection rating for the line to the infection rating of the wild type.