Petunia is a very important flower in the global floriculture industry and has played a critical role as a model in plant genetic studies. Owing to limited genetic variability in commercial germplasm, development of novel petunia phenotypes and new varieties has become increasingly difficult. To enrich petunia germplasm and facilitate genetic improvement, it is important to explore genetic variation in progenitor species that may contain highly valuable genes/alleles. In this study, an interspecific recombinant inbred population (168 recombinant inbreds) derived from Petunia integrifolia × P. axillaris were phenotyped for days to anthesis (DTA), flower count (Flower_C), flower diameter (Flower_D), flower length (Flower_L), plant height (Plant_H), plant spread (Plant_S), and plant size (Plant_Z) in 2014 and 2015. Transgressive segregation was observed for all traits in both years. The broad-sense heritability on a 2-year basis varied from 0.38 (Flower_C) to 0.82 (Flower_L). Ten QTL were consistently identified in both years and by two mapping strategies [multiple QTL mapping (MQM) in MapQTL and inclusive composite interval mapping (ICIM) in IciMapping]. Major QTL explained up to 30.2, 35.5, and 47.1% of the total phenotypic variation for Plant_S, Flower_L, and Flower_D, respectively. These findings should be of significant values for introgression of desirable genes from wild petunias into commercial varieties and future genetic improvement of this important flower.
Uncovering the genetics behind desirable traits in petunia plants could help improve commercial cultivars. While petunia plants are a key feature of the global horticultural industry, the limited genetic variability in commercial plants makes it difficult to improve desired plant traits. Zhanao Deng at the University of Florida, US, and co-workers conducted a genome-wide QTL identification study using a crossbred population combining two petunia species, P. integrifolia and P. axillaris. The team phenotyped the petunias in an open-air sub-tropical field rather than in an artificial environment like previous studies. They identified and characterized 17 genetic loci for seven important aesthetic traits, ranging from flower count to plant size. The petunia species had very different genetic backgrounds, likely stemming from their different geographic origins. The two species each can contribute novel genes for enhancing cultivated petunia cultivars.