ANALYSIS OF THE GENETIC DIVERSITY OF PHALAENOPSIS ORCHIDS WITH SINGLE NUCLEOTIDE POLYMORPHISMS AND SNAP MARKERS DERIVED FROM THE Pto GENE

Abstract

The Pto gene is a plant gene that has been reported to be involved in resistance to bacterial pathogens. A partial genomic sequence corresponding to Pto (~449 bp) was isolated from 16 species and four hybrids of Phalaenopsis during 2017 at the Department of Agronomy and Horticulture, IPB University, Bogor, Indonesia. Multiple sequence analysis was performed to find putative single nucleotide polymorphisms (SNPs) and design the corresponding single nucleotide-amplified polymorphism (SNAP) markers, which were in turn used to estimate the genetic diversity of 25 Phalaenopsis species. In total, 20 SNPs, of which 14 were nonsynonymous, were identified from the partial Pto sequences. Eighteen SNAP primers were then developed based on these 14 nonsynonymous and four synonymous SNPs. Validation results showed that 15 SNAP primers showed a polymorphism information content exceeding 0.3, suggesting the existence of more than two alleles for this locus. Upon their use, the SNAP markers described 86% of all interspecies variability. The Pto 52, Pto 349, Pto 229, and Pto 380 SNAP markers were very informative in the determination of genetic diversity. Notably, the existence of these nonsynonymous SNPs implied the possibility of functional changes within the amino acid sequence of the putative PTO protein. Thus, the resulting differences in the activity of the PTO protein may be used to breed tolerance to pathogen infection. Further work may be required to establish a functional link between tolerance to pathogens and the presence of Pto-SNAP markers in Phalaenopsis properly.