Biocontrol of root-knot nematode Meloidogyne incognita by Pseudomonas and Bacillus isolates on Pisum sativum

Abstract

Biocontrol of root-knot nematode Meloidogyne incognita was studied on Pisum sativum using isolates of fluorescent Pseudomonads (Pf1, Pa2, Pa3, Pa4 and Pf5) and Bacillus (B1, B2, B3, B4 and B5). Pseudomonas isolates caused greater inhibitory effect on hatching and penetration of M. incognita than caused by isolates of Bacillus. Among Pseudomonas, isolate Pf1 caused greater inhibitory effect on the hatching and penetration of M. incognita followed by Pa3, Pa4, Pa2 and Pf5. Similarly, among Bacillus isolates, B2 caused greater inhibitory effect on the hatching and penetration of M. incognita followed by B4, B3, B5 and B1. Pseudomonas isolates also caused greater increase in the growth of seedlings of pea than caused by isolates of Bacillus. In a greenhouse experiment, isolate Pf1 caused a greater increase in pea growth and higher reduction in galling and nematode multiplication followed by Pa3 and Pa4. However, isolate B1 was least effective in improving pea growth and reducing galling and nematode multiplication in greenhouse tests. Pseudomonas isolates were tested for siderophores, hydrogen cyanide (HCN) and indole acetic acid production because Pseudomonas isolates were more effective than the isolates of Bacillus in improving growth of pea and reducing galling and nematode multiplication. Only three isolates of Pseudomonas produced siderophores on Chrome-Azurol Sulphonate (CAS) agar medium out of five isolates tested. Isolates Pf1 showed greater production of siderophores followed by Pa3 and Pa4. Similarly, isolate Pf1 produced greater amount of IAA followed by Pa3, Pa4, Pa2 and Pf5. On the other hand, Pf1 and Pa3 showed greater production of HCN followed by Pa4 and Pa2 and Pf5. This study suggests that Pseudomonas isolate Pf1 may be used for the biocontrol of M. incognita on pea.