2018 ASHS Annual Conference

Sinningia speciosa (Gesneriaceae) is a perennial, herbaceous flowering plant native to the Atlantic Coastal Forests of Brazil. After the species was introduced into England in 1815 its cultivation as an ornamental house plant developed quickly. Within only a few short years it gained popularity across London and soon after specimens reached several parts of the world, including the U.S. Modern cultivars exhibit a broad range of phenotypes. Their large, colorful, upright, bell-shaped (actinomorphic) flowers differ markedly from the smaller, lavender, nodding (zygomorphic) flowers commonly found in the wild forms. Given its short history of cultivation, S. speciosa can serve as a model to understand the significant genomic changes that are associated with the process of plant domestication. The genome of the wild accession ‘Avenida Niemeyer’ (~ 400 Mb) was sequenced and assembled (PacBio corrected with Illumina reads) as a reference for subsequent alignments. A collection of 128 individuals within the tribe Sinningieae was genotyped using the Genoyping by Sequencing (GBS) method. Sixty-two individuals were S. speciosa (41 commercial cultivars and 21 wild accessions) and the remaining 66 represented 35 species sampled across the tribe. We retained 9,913 high quality non-missing SNPs across all species, and 25,083 within S. speciosa. Additionally, we phenotyped and genotyped (GBS) 160 individuals from an F₂ population derived from the cross of ‘Buzios’ (wild) by ‘Empress’ (cultivar). Principal component analysis on genetic distances clustered all the species according to the three major clades in the tribe: Sinningia, Corytholoma, and Dircaea. Cultivated and wild accessions of S. speciosa clustered together with no signs of interspecific hybridization events driving the process of domestication. We also detected a reduction of between 40 and 58% in genetic diversity across the cultivars relative to their wild counterparts. This bottleneck is likely the result of the limited number of individuals originally brought into cultivation (founder effect). In fact, distance clustering and ADMIXTURE analysis revealed only two wild accessions in the background of cultivated material: ‘Avenida Niemeyer’ and ‘Antonio Dias’. Quantitative Trait Loci analysis of flower symmetry (actinomorphic vs. zygomorphic) and flower color (purple vs. red) revealed highly significant single loci for each trait. Under the QTL responsible for flower symmetry we located a CYCLOIDEA-Like (CYC) gene with two small deletions that correlate with the trait. CYC encodes a transcription factor that controls floral symmetry in the snapdragon (Antirrhium majus).