In light of the results achieved by this investigation of B. subtilis and its metabolites as induced resistance agent to Aphis fabae and Rhopalosiphum padi, the following areas need to be explored:

To prove the role of serine in antibiosis mechanisms to the tested insects, a test should be conducted to attest the presence of secondary metabolites, especially proteinase inhibitors proteins in the phloem sap of the plant after it has been treated with the supernatants of B. subtilis strainsFZB 24, FZB 37 and FZB 38. The PIs proteins belong to the inhibitors proteins family that is capable of inhibiting the proteinases production by aphids, in order to decompose the plant proteins and liberate enough serine for the insect nutrition.

Furthermore, it should be investigated if the PIs found in the supernatant induced plants kill or block development and reproduction of aphids when added to their diet.

Identifying the PIs involved in induced resistance could serve as a useful compound, leading to the development of chemical control strategies and may also provide a valuable tool in the identification of cellular receptors involved in initiating the resistance.

Furthermore, we could show in our research that B. subtilis growth was better in sterile soil substrate, thus this offers the opportunity to treat seed material with B. subtilis FZB 37 as well as spraying the plant leaves with a solution of supernatant. Hence this full-bacterialized plant could be tested against A. fabae and R. padi opening a new perspective for biological plant protection means.