Growth of Tissue Cultured Oil Palm Plantlets (Elaeis Guineensis Jacq.) Inoculated with Plant Growth Promoting Rhizobacteria (PGPR)
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Date
2008-05
Authors
Che Om, Azlin
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Abstract
Twenty-nine isolates of N2 fixing rhizobacteria were successfully isolated from
oil palm roots (rhizoplane, rhizosphere and the root tissues). These diazotrophs were
successfully identified based on biochemical tests as Paenibacillus durus (formerly
known as P. azotoflXans), Paenibacillus po/ymyxa, Azospirillum /ipoferum,
Herbaspirillum seropedicae and Acetobacter diazotrophicus. The isolates produced
indole-3-acetic acid in the growth media. Experiments were carried out with the purpose
of observing the effects of PGPR inoculation on growth enhancement of tissue-cultured
oil palm. Results using oil palm embryoids showed that locally isolated
A. diazotrophicus (R12) and A. brasilense (Sp7) produce higher biomass (up to 1.51 and
2.37 g) and shoot formation (5) increment compared with the Control treatment
(+Sp7k). Moreover, the deleterious effects of bacterial inoculation on embryoids
developlnent could be delayed and eliminated through this technique. A. brasilense
(Sp7) and isolate Rl2 were also tested for the effectiveness to improve and induce
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rooting of oil palm shoots. The results indicated that inoculation of Sp7 and R12 on oil
palm shoots had enhanced shoot fresh weight (3.14 g), root fresh weight (0.10 g),
number of secondary roots (5) and higher leaf protein (25.88 mg BSAI ml protein) and
chlorophyll (0.24 mg chlorophyll / mg leaf fresh weight) contents compared to Control
treatment (+Sp7k). Furthermore, the plantlets inoculated with Sp7 and R12 also showed
associative nitrogen fixation activities that Sp7 could fix up to 0.965 Ilmol C214 g-I
fresh weight h-I ofN2 and R12 fixed N2 at 1.181 Ilmol C2H4 g-I fresh weight h-I. The
inoculated oil plantlets were then acclimatized in the glasshouse and successfully
showed high survival rate especially the plantlets inoculated with R12 (100% survival
rate). The plants were inoculated with Sp7 and R12 grown for 280 days (D280) in the
glasshouse. Results revealed that the plants inoculated with R12 showed the highest root
dry weight (10.5 g) and root volume (43.0 cm3
) compared to other treatments (+N, +Sp7
and +Sp7k). Besides that, higher leaf protein and chlorophyll contents were detected for
plants inoculated with R12 and Sp7 compared to the Control (+Sp7k) accounted 8.44
dan 8.53 mg BSA/ ml protein and 0.23 and 0.24 mg chlorophyll Img leaf fresh weight,
respectively. Positive influence of the inocula on growth of the host plants were due to
effective colonization ofSp7 and R12 on embryoid tissues and root surfaces of oil palm.
The results successfully showed that the tested diazotrophic rhizobacteria (Sp7 and R12)
could serve as biofertilizer in the form of microbial inoculants to improve growth of
tissue cultured oil palm plants.
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Keywords
Oil Palm , Plant Growth Promoting Rhizobacteria