Fig. 6

Potential regulatory mechanisms linking soil properties heterogeneity to fava beans phenotypes. A: Structural equation model (SEM) was constructed based on variables of rhizosphere soil elements, soil pH, relative abundance of metabolites and microbial genera, and fava beans phenotypes. The degree of path coefficient is proportional to the width of the arrow line, and the solid line means that a significant correlation was observed between the two variables (P < 0.05). The r² value represents the rate of variance explained for each variable. B: The standardized total effects (direct plus indirect effects) for each influential variable calculated by the SEM. Low chi-square, non-significant probability level (P > 0.05), high goodness of fit index (GFI > 0.90), low Akaike information criterion (AIC) and low root mean square error of approximation (RMSEA < 0.05) indicated that our data well matched the hypothesis model