## 3 Results  
### Analysis of _Cff_ VOCs Produced During In Vitro Culture  
More than 100 VOCs were identified as being produced in vitro by _Cff_ strains on both naturalized and synthetic culture media. Five major VOCs were evaluated as being exclusively produced in Cannellino bean flour by _Cff_ strains, i.e., 2-methyl-1-butanol/3-methyl-1-butanol, phenylmethanol, 6,10-dimethyl-5,9-undecadien-2-one, and 2-methoxy-4-vinylphenol (Figure 1) (Table S1). These compounds were chosen because they showed statistically significant differences in terms of production or degradation between the _Cff_-inoculated and non-inoculated samples. The only exception was the _Cff_ 50R strain, which was unable to produce 2-methoxy-4-vinylphenol. Another statistically significant and interesting finding was that benzaldehyde, which is naturally produced by legumes, was degraded by the _Cff_ strains in the inoculated samples, but not in the uninoculated samples.  
Interestingly, the VOC profiles produced by _Cff_ strains grown on naturalized media based on Cannellino or Borlotto bean flour were significantly different from those produced by _Cff_ grown on synthetic media (Figure 2), as well as from those produced by _Psp_ and _Xpp_ under the same cultural conditions (Table S2).  
Intriguingly, the same VOC composition was found in _Cff_ strains grown on naturalized media based on soybean, cowpea, pea, giant white bean, and lentil (Figure 3) flour, while a completely different VOC profile was produced by _Cff_ when grown in a durum wheat flour-based medium; wheat is not listed among _Cff_ plant hosts [44] (Figure 3). It is worth noting that the concentration of legume flour in the naturalized media tested did not affect the composition of the VOCs produced by _Cff_ (Figure 4).  
Figure 1: Chromatograms representing the VOCs emitted in the headspace of the vials containing a Cannellino naturalized medium uninoculated or inoculated with _Cff_ TS, _Cff_ 50R, _Cff_ P990, _Cff_ C7. Arrows point to the most significant VOCs, in color code mode: (blue) 2-methyl-1-butanol + 3-methyl-1-butanol; (red) benzaldehyde; (green) phenylmethanol; (violet) 6,10-dimethyl-5,9-undecadien-2-one; (orange) 2-methoxy-4-vinylphenol.  
Figure 3: Percentage of single VOC out of the total sum of the most abundant VOCs produced in vitro by _Cff_ strains (TS, 50R, P990, C7), _Psp_ and _Xpp_, on naturalized media made with flours of **(a)**_G. max;_ **(b)**_V. unguiculata;_ **(c)**_P. sativum;_ **(d)**_P. occcinues;_ **(e)**_L. culinaris;_ **(f)**_T. durum._ Compounds: (blue) 2-methyl-1-butanol + 3-methyl-1-butanol; (red) benzaldehyde; (green) phenylmethanol; (violet) 6,10-dimethyl-5,9-undecadien-2-one; (orange) 2-methoxy-4-vinylphenol. Values are the mean of nine replicates \(\pm\) percentage uncertainty.  
Figure 2: Percentage of single VOC out of the total sum of the most abundant VOCs produced in vitro by _Cff_ strains (TS, 50R, P990, C7), _Psp_ and _Xpp_, in **(a)**_P. vulgaris_ Cannellino and **(b)** Borlotto flour naturalized media, and in **(c)** LB, **(d)** NBY, **(e)** TBY synthetic media. Compounds: (blue) 2-methyl-1-butanol + 3-methyl-1-butanol; (red) benzaldehyde; (green) phenylmethanol; (violet) 6,10-dimethyl-5,9-undecadien-2-one; (orange) 2-methoxy-4-vinylphenol. Values are the mean of nine replicates \(\pm\) percentage uncertainty.  
According to the data obtained, phenylmethanol should be considered a potential key diagnostic marker for _Cff_, as it can differentiate _Cff_ from other seed-borne phytopathogenicic bacteria affecting beans, such as _Psp_ and _Xpp_ (Figures 2 and 3).