C. Production of antifungal compounds having antibiotic effects not related to membrane and cell wall effects

Where antibiotics have been described as powerful allies in the battle against bacterial contaminants, several molecules have been described which are fungicidal. The polyketide compound 2,4-diacetylphloroglucinol (DAPG) produced by P. fluorescens has received a particular consideration due to the broad spectrum activity against various fungal pathogens [43–46]. The molecule was isolated from Pseudomonas spp. strain F113 present in the rhizosphere of sugar beets [46] and has later been isolated from the rhizosphere of different crops [47]. DAPG has been shown to have antifungal effects against Fusarium and Alternaria spp. [48].

Although antibiosis has been proven to be a major weapon against plant pathogenic, fungal resistance might arise. One example is known for F. verticillioides in which a Lactamase encoding gene (FVEG\_08291) has been identified which enables the pathogen to resist benzoxazinoid phytoanticipins produced in plant but also possibly microbial xenobiotic lactam compounds [49]. This information therefore raises an important question about the ability of mycotoxigenic plant pathogens to cope with the antifungal compounds produced by BCAs. In case that reported fungal resistance may be present against BCAs, this may necessitate the continuous exploration of new antibiotics.
