Effects of nightly light treatment on the tomato defence resistance against DC3000. (A) Bacterial populations were measured at 1 hour and 3 days post-inoculation (OD = 0.1). Dark, no nightly light treatment; P, night lighting with purple light; B, night lighting with blue light; G, night lighting with green light; Y, night lighting with yellow light; R, night lighting with red light. The data represent mean values (± SD) of colony forming units (CFU) per square centimeter from five biological replicates, each replicate consisting of three leaf discs. Means denoted by the same letter did not significantly differ at p < 0.05 according to Duncan’s multiple range test. Initial bacterial numbers (1 hpi) was quantified to ensure the uniformity of inoculation of DC3000. (B) Photographs were taken 6 d after DC3000 inoculation; Microscopic lesions of representative tomato leaf samples at 3 days after DC3000 dipping (40-fold magnification). The experiment was repeated twice with similar results.