QTL analysis of heterostyly in Primula sieboldii and its application for morph identification in wild populations

Abstract

Background and aims: Primula sieboldii is a perennial clonal herb that is distributed around the Sea of Japan and is endangered in Japan. Its breeding system is characterized by heteromorphic self-incompatibility, and the morph ratio within a population is very important for reproductive success. The aims of this study were to construct a linkage map, map the S locus as a qualitative trait and quantitative trait loci (QTLs) for floral morphological traits related to heterostyly, and predict the morph type in wild populations by using molecular markers for devising a conservation strategy.

Methods: A linkage map was constructed with 126 markers. The QTLs for four floral traits and the S locus were mapped. Using the genotypes of loci that were located near both the S locus and the QTLs with large effects, morphs of 59 wild genets were predicted.

Key results: The linkage map consisted of 14 linkage groups (LGs). The S locus was mapped to LG 7. Major QTLs for stigma and anther heights were detected in the same region as the S locus. These QTLs exhibited high logarithm of the odds scores and explained a high percentage of the phenotypic variance (>85 %). By analysing these two traits within each morph, additional QTLs for each trait were detected. Using the four loci linked to the S locus, the morphs of 43 genets in three wild populations could be predicted.

Conclusions: This is the first report of a linkage map and QTL analysis for floral morphology related to heterostyly in P. sieboldii. Floral morphologies related to heterostyly are controlled by the S locus in LG 7 and by several QTLs in other LGs. Additionally, this study showed that molecular markers are effective tools for investigating morph ratios in a population containing the non-flowering individuals or during the non-flowering seasons.

Fig. 1.

Schematic diagram of the four floral traits investigated in this study. (1) Corolla tube length, (2) stigma height, (3) anther height, and (4) anther length.

Fig. 2.

Linkage map of P. sieboldii. Abbreviations: A, mapped using all individuals from both morph classes; L, mapped within a long-styled morph; S, mapped within a short-styled morph. Thick vertical lines indicate QTLs with P < 0·05; double vertical lines indicate suggestive QTLs (0·05 < P < 0·20).

Fig. 3.

Frequency distributions of the four traits assessed in the mapping population. Short-styled (Short) and long-styled morphs (Long) as indicated. Values on each graph show means and variances (in parentheses).