Figure 4.

Number of 16S rRNA gene copies per µl DNA (log scale) present in roots of nonsymptomatic (NS) and symptomatic (S) lettuce plants, collected at three hydroponic lettuce greenhouses, for the rhizosphere. Results are presented for the three greenhouses separately. The lower, middle and upper lines of the boxplots correspond to the first quartile, median and third quartile, respectively, while the whiskers represent the range from the minimum to the maximum. Data points represent the different replicates (number provided between brackets). Significant differences are indicated with one or more asterisks (P > .05 (ns), P ≤ .05 (*), P ≤ .01 (**), and P ≤ .001 (***)).