Abstract
Carthamus tinctorius L. (safflower) is an important oilseed crop producing seed oil rich in unsaturated fatty acids. Scarcity of identified marker-trait associations is a major limitation toward development of successful marker-assisted breeding programs in safflower. In the present study, a safflower panel (CartAP) comprising 124 accessions derived from two core collections was assayed for its suitability for association mapping. Genotyping of CartAP using microsatellite markers revealed significant genetic diversity indicated by Shannon information index (H = 0.7537) and Nei's expected heterozygosity (I = 0.4432). In Principal Coordinate Analysis, the CartAP accessions were distributed homogeneously in all quadrants indicating their diverse nature. Distance-based Neighbor Joining analysis did not delineate the CartAP accessions in consonance with their geographical origin. Bayesian analysis of population structure of CartAP demonstrated the unstructured nature of the association panel. Kinship analysis at population (Gij) and individual level (Fij) revealed absence of or weak relatedness between the CartAP accessions. The above parameters established the suitability of CartAP for association mapping. We performed association mapping using phenotypic data for eight traits of agronomic value (viz., seed oil content, oleic acid, linoleic acid, plant height, number of primary branches, number of capitula per plant, 100-seed weight and days to 50% flowering) available for two growing seasons (2011–2012 and 2012–2013) through General Linear Model and Mixed Linear Model. Our study identified ninety-six significant marker-trait associations (MTAs; P < 0.05) of which, several MTAs with correlation coefficient (R2) > 10% were consistently represented in both models and in both seasons for traits viz., oil content, oleic acid content, linoleic acid content and number of primary branches. Several MTAs with high R2-values were detected either in a majority or in some environments (models and/or seasons). Many MTAs were also common between traits (viz., oleic/linoleic acid content; plant height/days to 50% flowering; number of primary branches/number of capitula per plant) that showed positive or negative correlation in their phenotypic values. The marker-trait associations identified in this study will facilitate marker-assisted breeding and identification of genetic determinants of trait variability.
Highlights
Carthamus tinctorius L., commonly known as “safflower,” contains seed oil with significantly high levels of nutritionally desirable unsaturated fatty acids, which is unique among oilseed crops (Fernandez-Martinez et al, 1993)
The present study describes evaluation of a safflower panel of 124 accessions derived from two core collections for its suitability for association mapping and identification of Simple Sequence Repeats (SSRs) loci associated with eight traits of agronomic value in the crop
We merged accessions from these two core collections, removed redundancy (44 accessions were common to the two core collections) and included five Indian cultivars (Sharda, Manjira, Annigeri, PBNS-12 and TSF-1) assembling a final association panel with a non-redundant set of 124 accessions, which will hereafter be referred to as “CartAP” collection
Summary
Carthamus tinctorius L., commonly known as “safflower,” contains seed oil with significantly high levels of nutritionally desirable unsaturated fatty acids, which is unique among oilseed crops (Fernandez-Martinez et al, 1993). Safflower is cultivated in around 20 countries in a total area of 1,140,002 hectares and production of 948,516 tons (FAOSTAT). The major producers of safflower are the Russian Federation (286,351 tons), Kazakhstan (167,243 tons), Mexico (121,767 tons), USA (99,830 tons), Turkey (58,000 tons), and India (53,000 tons) accounting for ∼71% of total production (FAOSTAT). In spite of significant fluctuations in acreage under safflower cultivation, India was the highest average producer of the crop during 1994 to 2016. Safflower has not been able to create a niche for itself as a major oilseed crop. Genetic improvement of safflower is essential to increase its acceptability and utility as an oilseed crop of global importance
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