Design, Validation, and Application of Transcriptome-Based InDel Markers in Phalaenopsis-Type Dendrobium Varieties

The genetic improvement of Phalaenopsis-type Dendrobium, a valuable ornamental and medicinal orchid, is hindered by the lack of a complete reference genome. In this study, a transcriptome-based approach was employed to develop and validate insertion–deletion (InDel) markers for genetic analysis and variety identification. RNA-seq was performed on two distinct varieties, resulting in the de novo assembly of 156,108 unigenes. A bioinformatics pipeline was developed to identify 5083 high-quality InDel loci, from which 1029 potential markers were designed. Fifty primer pairs were selected and validated experimentally, with 84% successfully amplifying clear products, and 76% showing polymorphism. The polymorphism information content (PIC) of the markers ranged from 0.25 to 0.78, indicating their high potential for use in genetic diversity studies. These markers were used to classify 24 Phalaenopsis-type Dendrobium varieties into distinct genetic clusters. This work provides a scalable and robust platform for molecular breeding, DNA fingerprinting, and germplasm management in non-model species that lack a reference genome. By leveraging transcriptome data, these markers will contribute to the efficient genetic improvement of Dendrobium and other similar crops.