Efficacy of ozone and hydrogen peroxide on controlling crown gall bacterium and root knot nematode infected guava plants in Egypt

Abstract EN

Ozone gas (O 3), ozonated water (OW) and hydrogen peroxide (H 2 O 2) were tested in vitro and in vivo in different concentrations against four isolates of crown gall bacterium and one isolate of root-knot nematode.

The tested isolates were obtained from galled guava roots grown in Rosetta and Edkou farms, Beheira Governorate, Egypt.

Biochemical and physiological characterizations, tumorgenicity and molecular features of the four isolates proved that these isolates belong to Agrobacterium tumefaciens.

All concentration level of O 3 (50-450 ppm) gave bacteriostatic effect on bacterial cells as well as deactivated the tumor induction caused by Agrobacterium isolates.

However, all the tested concentrations describe previously of O 3 showed nematicidal effect against the second stage juveniles (J 2) of M.

incognita after 24 hrs of exposure.

In addition, tested concentrations of OW (15-135 ppm) showed bacteriostatic and nematicidal effect on A.

tumefaciens isolates and J 2 of M.

incognita, respectively.

On the other hand, all the tested concentrations (1, 3, 5, 7 and 9%) of H 2 O 2 showed bactericidal and nematicidal effects against A.

tumefaciens and J 2 of M.

incognita, respectively.

Scanning electron microscope photographs clearly showed the damage of A.

tumefaciens cells and J 2 of M.

incognita exposed to either O 3 or H 2 O 2 at concentrations of 450 ppm and 9%, respectively.