To identify the anti-Xanthomonas substances, single mutants of B. amyloliquefaciens deficient in production of surfactin (CH1), bacillomycin D (AK1), fengycin (AK2), bacillaene (CH6), macrolactin (CH7) difficidin (CH8) and a double mutant (RS6), blocked in synthesis of lipopeptides and polyketides and production of bacilysin, were tested.