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GENETIC DIVERSITY OF COCONUT SCALE INSECT, ASPIDIOTUS SPP. (HEMIPTERA: DIASPIDIDAE) FROM OUTBREAK AND NON-OUTBREAK AREAS IN THE PHILIPPINES USING RIBOSOMAL INTERNAL TRANSCRIBED SPACER 2 (ITS2)
Guerrero MS, Laude RP, Javier, PA and, Caoili BL
The genetic diversity of coconut scale insect (CSI), Aspidiotus spp., collected from outbreak and non-outbreak areas in the Philippines was investigated during the height of its infestation in 2013 to 2014 using the internal transcribed spacer 2 (ITS2) region of the ribosomal DNA (rDNA). Collection sites from outbreak areas included the provinces of Batangas, Cavite, Laguna, Quezon, and Basilan, Philippines, while non-outbreak area consisted of Aurora province. Samples of CSI from Indonesia were used as reference for Aspidiotus rigidus Reyne. Samples from outbreak areas were identified as A. rigidus, while CSI from non-outbreak area were identified as A. destructor Signoret. Results revealed six haplotypes for A. rigidus and two for A. destructor. Pairwise homology of A. rigidus haplotypes indicated 98.27 to 99.82% homology within species, while 99.65% was observed within A. destructor. Both Aspidiotus species have GC-rich ITS2 region (56 to 58%). The pairwise fixation index (Fst) showed strong genetic differentiation when outbreak and non-outbreak populations were compared (Fst = 1.0). Analysis of molecular variance (AMOVA) of the CSI populations showed a significant 94% genetic differentiation. CSI from outbreak and non- outbreak areas formed two distinct clades with 95 and 99% bootstrap value for A. rigidus and A. destructor, respectively, indicating high confidence for the groupings obtained in the phylogenetic analysis. This study showed that ITS2 can be used as an additional marker for the identification of Aspidiotus species. It also provides valuable information on the genetic differentiation of CSI species in the outbreak and non-outbreak areas that would be useful in the development of pest management strategies against CSI.