Biological control of root-knot nematode Meloidogyne incognita in pistachio using bacterial biocontrol agents

Root-knot nematode damage is one of the major challenges in Iranian pistachio production. In the current research, the potential of five isolates of Bacillus subtilis (B96, B95, B84, B48, B67) and Pseudomonas fluorescens VUPf52 were evaluated to manage root-knot nematode (RKN) Meloidogyne incognita in pistachio.

The experiment was conducted in a randomized complete block design with three replicates and different treatments depends on the assay.

In vitro experiments indicated that all B. subtilis treatments could kill second-stage juveniles with 100%, 63.80%, 63.33%, 87.14%, and 78.09% mortality at 72h, respectively. Under in vivo conditions, B96 and B95 were able to increase their population in the nematode infected soil more than other treatments. Compared to the control, these isolates also induced a significant decrease in the galling indices of nematodes, egg masses, and adult females per 0.5 gr of pistachio roots. Moreover, the results showed the significant effect of some treatments on the growth factors of pistachio plants. Bacterial suspension of B96 and P. fluorescens VUPf52 was applied as a soil drench under field conditions. Field assessments indicated that P. fluorescens VUPf52 was not significantly different compared with the negative control; although, B96 decreased the populations of second-stage juveniles (J2) the most.

It is concluded that B. subtilis products have the potential to be one of the components in the integrated RKN management in pistachio. Bacterial efficacy on M. incognita in pistachio orchards is reported here for the first time.