Effect of Certain Biocontrol Agents on The Root-Knot Nematode and Some Enzymatic Activities in Tomato Rhizosphere

Root-knot nematodes (Meloidogyne spp.) are a group of the most destructive plant pathogens of tomato plants. Biological control is considered a safe and efficient tool to control these pathogens. The present study aimed to evaluate the potency of the marine algae (Ulva fasciata) and two bacterial isolates isolated from the seeds and rhizosphere of tomato plants against the root-knot nematode, M. incognita, infecting tomato plants. The bacterial isolates were identified using polymerase chain reaction (PCR) through the amplification of 16S rRNA as Bacillus amyloliquefaciens (PQ821314) and Serratia marcescens (PQ012666). B. amyloliquefaciens and S. marcescens were used @ 108 CFU/ml, while U. fasciata was used @ 5000, 2500, 1250 and 625 mg/l concentrations in vitro. A comparable treatments included; Nemacross© 2% and oxamyl 24% (SL) beside the nontreated check. Results showed that B. amyloliquefaciens, S. marcescens, U. fasciata and oxamyl significantly reduced (P ≤ 0.05) egg hatching of M. incognita and increased (P ≤ 0.05) the mortality of M. incognita J2s, compared to the control checks. However, Nemacross© gave effects on larval mortality 25.30 and egg hatchability 35.82 %. Under greenhouse conditions, the disease severity (root galling) and the nematode reproduction (no. egg mass/plant) of M. incognita were greatly suppressed by all treatments. Maximum reduction of root galling (98.77%) and nematode reproduction (99.10%) was obtained by B. amyloliquefaciens. Fresh weights of shoot and root systems were generally increased by the application of the nematicide oxamyl and all the tested bioagents compared to the control treatment (M. incognita).