GENETICAL STUDIES AND ANTAGONISTIC EFFECTS OF A NEWLY BACTERIAL FUSANT AGAINST MELOIDOGYNE INCOGNITA, ROOT-KNOT NEMATODE, AND A PLANT PATHOGEN FUSARIUM OXYSPORUM INFECTING SUNFLOWER

Abstract

All tested bacterial concentrations of P.aeruginosa and fusant strain (Psa::Psf),
between Pseudomonas fluorescens and Pseudomonas aeruginosa, affected
Meloidogyne incognita juveniles J2 survival in invitro. The mortality percentages of
nematode were dependent on the bacterial concentration and exposure time. The fusant
strain (Psa::Psf), was used as soil drench or as seed soaking for controlling root-knot
nematode Meloidogyne incognita, which was associated with sunflower plant
(Helianthus annus) under greenhouse conditions. The fusant strain proved to be more
effective than its parental strain, P. aeruginosa, in reducing different nematode
parameters(give names) as well as enhancement of plant growth. Soil drench treatment
was more effective in controlling root-knot nematode than the seed soaking treatment.
The genetic stability of antagonist against Fusarium oxysporum of the fusant and its
parental strain were 83% and 72%, respectively. RAPD-PCR studies indicated the
same DNA-patterns among the fusant and its reisolated offspring. Three fusant isolates
were selected, from which two isolates showed the same band when using two primers,
while one isolate did not produce any band. Plasmid profile studies revealed the
occurrence of one plasmid, of about 23 kb, in the fusant and its offspring while no
plasmid has been found in the parental strain. The corresponding genes of antagonist
against Fusarium oxysporum were located on the bacterial chromosome. From the
present results, it could be advised to use modified genetically bacteria for
management of the root-knot nematode.