Linkage map construction and QTL mapping for morphological traits in Ipomoea trifida, a diploid sweetpotato relative.

Ipomoea trifida G. Don (2n = 2x = 30) is considered the closest known diploid relative and a wild ancestor of the autohexaploid sweetpotato, Ipomoea batatas (L.) Lam. (2n = 6x = 90). This study aimed to map quantitative trait loci (QTLs) in a diploid full-sib population (M9 × M19) consisting of 210 progenies based on a high-density genetic linkage map constructed with single-nucleotide polymorphisms (SNPs). In a randomized complete block design with four replications, the phenotypic evaluation of 11 morphological traits was conducted for 188 individuals in 2016 at the International Potato Center under screenhouse conditions in San Ramón, Peru. Heritabilities ranged from 0.30 to 0.80, and genetic correlations varied from -0.22 to 1. An integrated genetic map was constructed with 15 linkage groups and 6410 SNPs spanning 2440.47 cM using the Onemap v.3.0 R package. Major misassemblies were identified and properly fixed on chromosomes 2, 3, and 7. QTL mapping was performed using the composite interval mapping approach for each trait with fullsibQTL v.0.0.901 R package. A total of 37 QTLs were identified, with up to 42.39% of the proportion of phenotypic variance explained by a major QTL on chromosome 3 for a leaf shape-related trait. Reference genome refining and QTL-linked markers contribute to advancing genetic and genomic research on I. trifida and may support sweetpotato breeding programs targeting ornamental traits.