Effects of crude antibiotic of Bacillus subtilis on hatching of eggs and mortality of juveniles of Meloidogyne incognita
AbstractThe endospore-forming rhizobacterium Bacillus subtilis produces more than two dozen lipopeptide antibiotics, hydrolytic enzymes and other secondary metabolites. The biocontrol activity of Bacillus strains against multiple plant pathogens has been widely documented. Three families of Bacillus lipopeptides (surfactins, iturins and fengycins) are the most studied for their antagonistic activity against a wide range of phytopathogens, including bacteria, fungi and nematodes. The root-knot nematode, Meloidogyne incognita, is one of the most damaging pathogens, attacking a wide range of crops. Therefore, six antagonistic endophytic strains of B. subtilis viz., Bs N 1, Bs N 3, Bs N 4, Bs N 7, Bs 5 and Bs N 11, were isolated from noni plants and tested for their nematicidal activity against M. incognita. The strain Bbv 57, isolated from banana and known to have nematicidal activity, was included in the study as a control. The genomic DNA of the Bacillus strains was isolated and amplified by PCR to identify antibiotic genes. Biosynthetic gene specific primers amplified a 440 bp fragment of surfactin gene from BsN 3, Bs 5 and Bbv 57 and a 648 bp fragment of iturin gene from Bs 5 and Bbv 57. Bs 5, with high surfactin and iturin activity, suppressed hatching of eggs and killed second stage juveniles of the nematode under in vitro conditions.