Abstract:
Root
-
knot nematodes are the most economically important plant pathogens in pistachio. The
ability of
Pseudomonas fluorescens
strains VUPF5, VUPF52,
Bacillus cereus
strain PRC95 and
Bacillus subtilis
strain PRC96 were tes
ted as biocontrol agents for
Meloidogyne incognita
on
the pistachio cultivars Sarakhs and Badami. The effect of these bacterial strains on defense
-
related enzymes activity in pistachio was also investigated. Pistachio seedlings of both cultivars
were treat
ed with bacterial strains and then were inoculated with 2000 second
-
stage juveniles
of nematode after two days. Evaluations were made for changes of Peroxidase (POX),
PolyPhenolOxidase (PPO), Phenylalanine Ammonia lyase (PAL) and Total Phenolic Content
(TP
C) determined at 2, 4, 7, and 10 Days After nematode Inoculation (DAI). Results showed
improved activity of POX, PAL and PPO in both cultivars. The most significant result for
POX activity in the treated seedlings belonged to
Pseudomonas
strain VUPF5 at 7
DAI for
Sarakhs and 10 DAI for Badami. However, this strain displayed an increase in PAL activity at
2 and 4 DAI in Badami and Sarakhs, respectively. Seedlings treated by the
Pseudomonas
strain
VUPF52 at 10 DAI had the highest PPO activity among cultivars.
TPC concentration was
slightly higher, by 8.4% at 4 DAI, in Sarakhs seedlings treated with VUPF5, but no significant
increase could be seen in the Badami cultivar compared with the control. In another
experiment, 4 months after nematode inoculation in see
dlings of both cultivars treated by
bacterial strains, numbers of galls, egg masses, and second juveniles decreased compared with
the non
-
treated seedlings.
Keywords
: Bacillus subtilis,
Pistachia vera
cvs.
Badami and Sarakhs, , Root knot nematode.
