Figure 1

Spectrum of effectiveness of Pseudomonas aeruginosa 7NSK2- and Serratia plymuthica IC1270-triggered ISR in rice. ISR was induced by growing the plants in soil containing 7NSK2 or IC1270 bacteria. Control plants were treated with water. (A) Quantification of ISR against M. oryzae. Plants were challenged when 4 weeks old by spraying a spore suspension of virulent M. oryzae VT7. Six days after challenge inoculation, disease was quantified by counting the number of susceptible-type lesions per leaf 4 and the level of induced protection was calculated relative to challenged control plants. Photographs depicting representative symptoms were taken 7 days post inoculation. Bar = 10 mm. (B) Quantification of ISR against R. solani. Four-week-old plants were challenged by placing a 1 cm-toothpick colonized by R. solani inside the sheath of the second youngest fully developed leaf; 4 days later, disease severity was assessed by measuring the total length of sheath blight lesions. (C) Quantification of ISR against C. miyabeanus. Plants were challenge-inoculated when five weeks old by spraying a conidial suspension. Disease evaluation was performed 4 d postinoculation, using a 1-to-5 disease severity scale as described in the Methods section. For all graphs, statistical analysis was performed on pooled data from at least four independent experiments, because interaction between treatment and experiment was not significant at α = 0.05 and variances were homogeneous. Different letters indicate statistically significant differences between treatments according to non-parametric Kruskall-Wallis and Mann-Whitney tests (n ≥ 42; α = 0.05).