Fig. 3

Presence of sul1 and sul2 genes, normalized to the total 16S rRNA genes and expressed in ΔCt values, in rhizosphere soils (respectively, dark and light blue) and roots (respectively, dark and light brown) of lettuce (A), leek 2018 (B) and leek 2019 (C). *, indicate significantly lower than sul1 ΔCt values (P = 0.002) of the other soil treatments; $, indicate significantly higher than sul2 ΔCt values of the other soil treatments (P = 0.01). Significance of difference between mean sul1 and sul2 ΔCt values, over all soil treatments were: P < 0.001 (sul1 > sul2, LSD = 0.33) for lettuce rhizosphere soil; P = 0.002 (sul1 > sul2, LSD = 0.22) for leek 2018 rhizosphere soil; P = 0.046 (sul1 < sul2, LSD = 0.45) for leek 2019 rhizosphere soil; P < 0.001 (sul1 > sul2, LSD = 0.53) for lettuce roots; P = 0.07 (sul1 = sul2), for leek 2018 roots; P = 0.003 (sul1 < sul2, LSD = 0.54) for leek 2019 roots