1.Bacillus thuringiensis isolated from soil in oil palm plantation with high toxicity against Oryctes rhinoceros larvae
Flatya Indah Anggraini ; Maria Sugiharti ; Antonius Suwanto ; Nisa Rachmania ; Bibiana Widiawati Lay
Malaysian Journal of Microbiology 2021;17(4):345-351
Aims:
Oryctes rhinoceros beetle is one of the most damaging pests of oil palm and cause high oil palm mortality. The
empty fruit bunch mulch and rotten old trunk of oil palm in the field provide the organic matter for the breeding sites and
increases the number of O. rhinoceros larvae. Bacillus thuringiensis as bioinsecticide can synthesize crystal proteins
toxic to the larvae. The present study was aimed to find effective B. thuringiensis isolates as biopesticide against O.
rhinoceros larvae.
Methodology and results:
Screening process was carried out through heating of soil sample suspension at 80 °C to
eliminate the non-spore formers and plated onto T3 medium. Colony morphology was observed, followed by Gram and
endospore staining. The crystal protein was observed by Coomassie Brilliant Blue (CBB) staining. Bioassay test was
conducted by force-feed method followed by food contamination method. The results showed isolates SBB33 and
SBB35 were able to infect and caused high mortality to the O. rhinoceros larvae. Isolates SBB33 and SBB35 showed
the highest mortality against 1st instar larvae (94.44% and 75% respectively) and 3rd instar larvae (64.8% and 60%
respectively) compared to control treatments. The 16S rRNA gene sequencing showed SBB33 has high similarity with B.
thuringiensis strain 3S2-3, while SBB35 has high similarity with B. thuringiensis strain GCU_BTi10. Protein separation of
the spore-crystal mixture by SDS-PAGE showed the prominence of 66 kDa protein band that was predicted to be Cry
toxins which is specific to coleopterans insect.
Conclusion, significance and impact of study
Bacillus thuringiensis isolates SBB33 and SBB35 have high potential
as biopesticides against O. rhinoceros larvae and could be used to control major pests in oil palm plantation.
Bacillus thuringiensis--isolation &
;
purification
;
Coleoptera