Tuesday, August 9, 2016
Georgia Ballroom (Sheraton Hotel Atlanta)
Impatiens downy mildew (IDM), incited by Plasmopara obducens, is a devastating disease to the bedding plant and landscape industries in the United States and many other countries in the world. A good understanding of the molecular basis for the IDM resistance in New Guinea impatiens (Impatiens hawkeri) and its interspecific hybrid cultivars (Impatiens xhybrid hort) is of significant value for genetic improvement of garden impatiens (Impatiens walleriana) for resistance to IDM. This study was conducted to reveal the differences in gene expression between leaves of I. walleriana cv. Super Elfin® XP Pink and I. xhybrid hort cv. SunPatiens® Compact Royal Magenta, which are susceptible and resistant to IDM, respectively. Total RNA was extracted from fully expanded leaves of the two cultivars and their leaf transcriptomes were sequenced on Illumina HiSeq2000. Transcriptome assembly resulted in 121,497 unigenes with an average length of 1,156 nucleotides and N50 of 1,778 nucleotides. A total of 78,919 unigenes were differentially expressed between the two cultivars. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Clusters of Orthologous Groups (COG) database searches predicted that 248 and 758 of the differentially expressed unigenes were related to plant immunity or defense. A total of 22,484 simple sequence repeats (SSRs) were identified in these unigenes, and trinucleotide SSRs, especially the AAG/CTT type, were most common. Searching for single nucleotide polymorphisms (SNPs) resulted in the identification of 245,936 and 120,073 SNP sites in SunPatiens® Royal Magenta and Super Elfin® XP Pink, respectively. The A-G and C-T transition type SNPs were most common in both cultivars. The obtained transcriptome sequences, the list of differentially expressed genes, and the SSR and SNP sites will be used to identify the gene(s) that are responsible for the resistance to IDM in I. hawkeri and its interspecific hybrids.