Plant growth-promoting rhizobacterium (Paenibacillus polymyxa) induced systemic resistance in tomato (Lycopersicon esculentum) against root-knot nematode (Meloidogyne incognita)

Three strains of plant growth-promoting rhizobacteria, Paenibacillus polymyxa GBR-447, GBR-477 and GBR-501 were tested in potted soil under greenhouse conditions for their ability to induce systemic resistance in tomato (Lycopersicon esculentum Mill.) roots against root-knot nematode (Meloidogyne incognita). The application of bacterial suspensions of these strains of P. polymixa into potted soil at the rate of 5ml (108CFU/ml)/plant significantly reduced penetration rate of incognita juveniles (J2) into tomato roots and gall formation, inhibited giant cells formation and enhanced plant growth significantly. Strain GBR-447 was the most effective, as J2 penetration into tomato roots reduced by 46.4%, 52.5 and 55.8% after 5, 10 and 25 days of J2 inoculation, respectively. The lowest effect was observed in pots treated with GBR-501, wherein J2 penetration reduced by 15.2%, 17.7% and 26.5% after 5, 10 and 25 days of J2 inoculation, respectively. Application of bacterial suspension of GBR-447 and GBR-477 to one-half of the split root system caused systemic reduction in the number of J2 penetration in the untreated other half of the split root system and inhibited giant cells formation. Penetration of J2 was reduced by 38.3-44.2%, 45.7-52.5% and 51.3-54.3% after 5, 10 and 25 days of J2 inoculation, respectively. GBR-501 inhibited J2 penetration up to 22.8% on 25th day of inoculation.