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CROP BREEDING & GENETICS

Quantitative Trait Loci Analysis of Endosperm Color and Carotenoid Content in Sorghum Grain

^a 157 Biotechnology Bldg., Dep. of Plant Breeding and Genetics, Cornell Univ., Ithaca, NY 14853
^b Institute for Genomic Diversity, 156 Biotechnology Bldg., Cornell Univ., Ithaca, NY, 14853
^c USDA-ARS, Plant, Soil, and Nutrition Lab., Dep. of Plant Breeding and Genetics, Cornell Univ., Ithaca, NY 14853
^d Dep. of Soil & Crop Science, Texas A&M Univ., 2474 TAMU, College Station, TX 77843-2474
^e Dep. of Agronomy, 2004A Throckmorton Hall, Kansas State Univ., Manhattan, KS, 66506
^f Institute for Genomic Diversity, 158 Biotechnology Bldg., Cornell Univ., Ithaca, NY 14853

^* Corresponding author (sk20{at}cornell.edu).

Vitamin A deficiency affects approximately 250 million people in semiarid regions of Africa and Asia, where sorghum (Sorghum bicolor Moench) is a major staple crop. Yellow endosperm sorghums contain carotenoids, some of which can be transformed by humans into vitamin A. Our objective was to study the genetic basis of variation in carotenoid levels in sorghum endosperm by mapping quantitative trait loci (QTL) associated with carotenoid content and endosperm color, as a putative predictor of carotenoid concentration. A recombinant inbred line population developed from a yellow (‘KS115’) by a white endosperm (‘Macia’) parental cross was evaluated in two locations in 2005. A genetic map was generated using 112 molecular markers including nine carotenoid candidate genes. Lutein, zeaxanthin, and β-carotene were the major carotenoids identified. Several QTL were detected for each compound as well as for color and total carotenoids. Color was significantly correlated with the levels of all compounds, and color QTL co-localized with carotenoid QTL. For β-carotene (provitamin A), five QTL were localized on chromosomes 1, 2, and 10. One of them, on chromosome 2, was stable across both environments, had positive additive effects (1.179 and 1.379), explained large proportions of the phenotypic variance (11.6% and 15.15%), and was associated with a new phytoene synthase gene (Psy3). This first report of QTL for carotenoid content in sorghum grain provides a starting point for breeding high-provitamin A sorghums.

Abbreviations: CCD, carotenoid cleavage dioxygenase • CIM, composite interval mapping • CRTISO, carotenoid isomerase • GGDP, geranylgeranyl diphosphate • HPLC, high performance liquid chromatography • INDELS, insertion or deletion • LCYB, lycopene β-cyclase • LCYE, lycopene -cyclase • LOD, logarithm of the odds • LR, likelihood ratio • MAS, marker-assisted selection • PDS, phytoene desaturase • PSY, phytoene synthase • RFLP, restriction fragment length polymorphism • RIL, recombinant inbred line • SMA, single marker analysis • SSR, simple sequence repeat • QTL, quantitative trait loci • ZDS, -carotene desaturase • ZISO, 15-cis--carotenoid isomerase