Fig. 5

Phytotoxins produced by Dickeya strains. a, Bioassay of toxin production. b, Inhibitory activity of toxins from Dickeya strains against rice seed germination. Bacteria were grown in LB medium till OD₆₀₀ = 1.5, and 20 seeds of rice variety CO39 were added to 5 ml of every bacterial culture and incubated at room temperature for 5 h, which were then cleaned and transferred onto a Petri dish with filter paper on it, and then incubated at 28 °C under 16 h light and 8 h dark conditions. Rice seeds incubated with same amount of D. dadantii 3937 were used as a control. c, The toxin produced by MS2 is an extracellular nonprotein metabolite. Strain MS2 was grown in LS5 medium till OD₆₀₀ = 1.5 (c), and supernatant of the culture (s) was collected, which was treated by boiling at 100 °C for 10 min (b) or digestion with protease K at 37 °C for 30 min (k). Finally, the inhibition activity against the growth of E. coli DH5α was measured. d, PCR detection of zeamines biosynthesis genes from zmsO to zmsN. Based on the coding sequences of zms gene cluster in strain EC1 [43], 18 pairs of primers corresponding to zmsO to zmsN were designed to detect the zeamine biosynthsis gene cluster in D. zeae strains, which are presented in Additional file 4. The DNA marker is DL2000