Construction of the First Genetic Linkage Map and QTL Analysis for Morphological Traits in Bougainvillea glabra Choisy

Bougainvillea (Bougainvillea glabra) is a perennial woody species belonging to the Nyctaginaceae family, native to South America. It is widely recognized for its brightly colored bracts and strong adaptability, and is widely cultivated as a major ornamental plant in tropical and subtropical regions. However, QTL mapping studies on morphological traits remain limited in the genus Bougainvillea, and the genetic basis underlying its key ornamental traits is still largely unclear. In this study, an F1 segregating population was constructed using the cultivars ‘Mrs Eva White’ and ‘Formosa’ as parents, and was used for high-density genetic map construction and quantitative trait locus analysis. Fourteen leaf and thorn-related traits were investigated, with coefficients of variation ranging from 8.16% to 64.54%. Based on specific-locus amplified fragment sequencing (SLAF-seq), a total of 1,133,206 SLAF markers were developed, among which 479,488 were polymorphic. Using the inclusive composite interval mapping (ICIM) algorithm in the GACD 1.2 software, a high-density genetic linkage map was constructed for B. glabra, consisting of 17 linkage groups and 3256 markers. The genetic map spanned 1797.64 cM, with an average marker interval of 0.55 cM. A total of 22 QTLs were detected for the measured leaf and thorn traits, including 16 major QTLs with a PVE ≥ 8%. Collectively, this study identified stable genetic loci for important morphological traits and provides a valuable theoretical foundation for marker-assisted selection and genetic improvement of ornamental traits in Bougainvillea.