LOCALIZATION OF QTLs FOR DOMESTICATION-RELATED TRAITS IN SUNFLOWER

Abstract

Improvement of cultivated sunflower (Helianthus annuus L.) depends largely on the introduction of genetic diversity from wild species. The purpose of the present study was to construct a linkage map based on AFLP markers from an F_2:3 population derived from a sunflower inter-subspecific cross (H. annuus var. macrocarpus x H. annuus ssp. texanus Heiser), as well as to detect quantitative trait loci (QTL) positions by interval mapping. The following contrasting traits between cultivated and wild sunflowers, putatively related to domestication, were evaluated: plant height, head number (branching), and head diameter per plant, number and weight of achenes per head, days to flowering, days to physiological maturity, and seed oil content. The phenotypic evaluation was carried out in field conditions, by using an incomplete block design with two replications. A genome-wide statistical significance of 0.05 was used to detect QTLs. To establish the empirical significance threshold values, permutation tests were performed only in linkage groups showing a LOD (logarithm of odds) score >1.5. Moreover, single marker analyses using analysis of variance per unlinked individual locus for each trait were carried out, which identified four unlinked loci for number of achenes per head and days to physiological maturity with P < 0.001. We identified one QTL with genome-wide significance of 0.017 for achene weight, which could be representative of a genome region produced by domestication, plus five putative QTLs in five characters. All the detected QTLs, including putative ones at the chosen significance level, explained from 7.1 to 11.9 % of the phenotypic variance.