2019 ASHS Annual Conference

Petunia hybrida is an important flower in the floriculture industry. Fungal and virus diseases pose a major threat to petunia plants in commercial production and landscape use. Improving disease resistance has become an important objective in petunia breeding. The nucleotide-binding site leucine-rich repeat (NBS-LRR) genes play an important role in recognizing pathogens and conferring disease resistance in plants. The released genomes of P. axillaris and P. inflata, the two parental species of P. hybrida, have made it possible to conduct a comprehensive characterization of this group of disease resistance genes in Petunia in a genome-wide manner. Using multiple bioinformatic tools, we discovered a total of 267 and 388 NBS genes in the genomes of P. axillaris and P. inflata, respectively. These NBS genes were characterized for the presence of the Toll/Interleukin-1 receptor (TIR), coiled coil (CC) and/or LRR domains. For all classes of NBS genes, there are more genes in P. inflata than in P. axillaris. Surprisingly, most of the Petunia NBS genes are of the non-TIR type, and only very few of the TIR type. More than half (55.9%) of the NBS genes contain the LRR domain while the remaining lack a typical LRR region. P. inflata has 146 CC-NBS-LRR genes, more than double of the number (68) in P. axillaris. With further phylogenetic and gene expression analysis, our study shall provide important insights into disease resistance in Petunia and a valuable genomic resource for future improvement of disease resistance in this important flower. This resource may enable Petunia to become a new model system for molecular genetic study of disease resistance genes in plants.