Identification of quantitative trait loci associated with yield-related traits in sweet potato (Ipomoea batatas)

Yield-related traits in sweet potato are generally thought to be quantitative inheritance traits significantly affected by variations in environmental factors. The objective of this study was to identify inter simple sequence repeat (ISSR) markers linked to top weight, root weight, root number, root shape, root skin color, and flesh color in the sweet potato (Ipomoea batatas). Two mapping populations of nearly 120 F₁ plants were derived from a reciprocal cross between 'Nancy Hall' (NH) and 'Tainung 27' (TN27). In total, 100 ISSR primers were screened, among which 18 were identified with scorable polymorphic bands that were amplified. All of these primers were anchored at the 3′-end with 7 different types of dinucleotide, and 90.7% of them were segregated as simplex markers. Two partial linkage maps in the sweet potato which use simplex and double-simplex ISSR markers were constructed. The length of each linkage group spanned a very wide range of 10.7∼149.1 centiMorgans (cM). These maps consist of 37 NH and 47 TN27 markers with map lengths of 479.8 and 853.5 cM, respectively. The ISSR markers were fitted to a 3:1 ratio of simplex and duplex segregation for the parental alleles, as the sweet potato was expected to be autohexaploid. Fourteen and nine quantitative trait loci (QTL) linked to specific ISSR markers were detected for traits in (NH × TN27) and (TN27 × NH), respectively. Twenty-two of these QTL-mapped markers were unique to the specific traits, and two were linked to two traits in each linkage map. These markers appear to be applicable to crop improvement.