Characterizing Crop Timing and Quality Traits of an Interspecific Hybrid Petunia axillaris × P. exserta F7 Recombinant Inbred Line Population

Petunia (Petunia ×hybrida) has consistently ranked among the top three bedding plants sold in the United States. Previous studies indicate that using wild species can improve commercial cultivars by providing new alleles for desired traits such as development rate and flower bud number. An interspecific P. axillaris × P. exserta F7 recombinant inbred line (RIL) population was developed and 171 RILs and the parental species were phenotyped for a wide range of crop timing and quality traits at 14, 17, and 20°C under a 16-h photoperiod.  Additionally, days to flower was evaluated under a 9-h photoperiod at 20°C only.  The number of nodes on the main stem was counted 0, 14, and 28 days after treatments (DAT) began and used to calculate development rate. The population exhibited transgressive segregation for all crop timing and quality traits evaluated.  Days to first flower ranged from 31 to 62, 37 to 70, and 46 to 93 DAT at 20°C, 17°C, and 14°C respectively.  Average flower bud number at first flowering increased from 13 to 26, and the number of flowering branches increased from 6 to 9, as temperature decreased from 20°C to 14°C.  Total flower bud number at first flowering ranged from 2 to 44, 1 to 65, and 8 to 73 for plants grown at 20°C, 17°C, and 14°C, respectively.  Days to first flower was positively correlated to total flower bud number, number of branches with flower buds, and node number below the first flower at all temperatures.  A high-density single nucleotide polymorphism-based genetic linkage map for this population has been generated using genotyping-by-sequencing. These phenotypic data will serve as the foundation for future QTL mapping and candidate gene identification efforts for crop timing and quality traits of interest.