Development of immune gene-linked SSR markers for coconut scale insects (Aspidiotus destructor and Aspidiotus rigidus) toward comprehensive genetic analysis

The infestation of coconut scale insects, Aspidiotus destructor and A. rigidus, resulted in significant economic damages to the Philippine coconut industry in recent years. This incident demands a thorough understanding of the biological information of these insect pests, to understand how they thrive and perpetuate despite adverse ecological conditions. In this study, 22 and 302 immune gene orthologs were identified in A. rigidus and A. destructor, respectively. This result confirms the expression of evolutionarily conserved immune pathways (i.e., Toll, Imd, JNK, and JAK- STAT) in Aspidiotus spp. Genic SSRs were also mined and characterized in the transcriptome datasets, wherein dinucleotide and trinucleotide SSRs composed of AT/TA and AAT/ATT homopolymers were most abundant. It had an average length of 40 bp and density of 728 SSRs/Mbp for both species. Moreover, a total of 18,480 and 1,681 genic SSR markers were designed for A. destructor and A. rigidus, respectively. From these vast resources of markers, eight (8) immune gene-linked SSR markers were deduced targeting four (4) specific genes such as effete (eff), autophagy 8 (Atg8), ras-like GTP-binding protein (rho1) and anterior open (aop). These markers were successfully amplified in representative samples demonstrating their potential utility for a comprehensive genetic and functional diversity analysis of coconut scale insects.