FIGURE 1.

Virulence of the natural variants of Clavibacter capsici. (a) Disease severity of C. capsici isolates in comparison to the previously type strain PF008 and its pCM1_Cc‐lacking derivative (ΔpCM1_Cc). (b) Representatives of necrotic symptoms on the infected leaves with low‐virulence isolates. All inoculated leaves were photographed at 7 days after inoculation (dai). (c) Quantification of the disease severity in pepper leaves infected with low‐virulence isolates. Disease severity was expressed as a percentage compared to strain PF008‐infected leaves. C. capsici PF008 and natural isolate 1,003, and mock treatment with MgCl₂ were used as positive and negative controls, respectively. Six leaves from three independent plants were used per treatment. Bars indicate SE. Different letters indicate statistically significant differences in disease severity, which was analysed by a nonparametric Kruskal–Wallis test with Dunnett's multiple comparisons (p < .05). (d) Bacterial growth of C. capsici isolates in pepper plants. The bacterial growth was measured at 3 and 5 dai. Bars indicate SD. All experiments were repeated three times and similar results were obtained. (e) Growth curves of low‐virulence C. capsici isolates and a pCM1_Cc‐lacking strain (ΔpCM1_Cc) on media. Optical density at 600 nm (OD₆₀₀) was measured from 0 to 50 hr. The different letters in (d) and (e) indicate statistically significant differences as determined by Duncan's multiple range test (p < .05)