ARS | Publication request: A Consensus Linkage Map that Identifies Genomic Regions Controlling Beta-Carotene Quantity and Fruit Maturity in Melon (Cucumis Melo L.)

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 3, 2009
Publication Date: August 15, 2010
Citation: Cuevas, H.E., Staub, J.E., Simon, P.W., Zalapa, J.E. 2010. A Consensus Linkage Map that Identifies Genomic Regions Controlling Beta-Carotene Quantity and Fruit Maturity in Melon (Cucumis Melo L.). Theoretical and Applied Genetics. 119:741-756.

Interpretive Summary: Carotenoids are a class of compounds produced by most photosynthetic (undergoing conversion of light to chemical energy which allows for plant life) organisms that are essential to both plants and animals. Thus, they play essential functions in plants. Some carotenoid pigments (e.g. a-carotene, B-carotene) are important for human health and nutrition due to their function in Vitamin A biosynthesis (a vitamin essential for human health). Strong evidence suggests that diets rich in carotenoids (e.g. B-carotene Lycopene) can prevent the onset of some chronic diseases and certain cancers (e.g. prostate cancer). Melon is an economically important vegetable species that is grown worldwide with variable amounts of Vitamin A depending upon the market class (e.g., cantaloupe and honeydew) and growing environment. Fruit of orange-fleshed market types [e.g., U.S. Western Shipping cantaloupes) are a rich source of dietary carotenes (primarily B-carotene), therefore, is an important source of Vitamin A. It would be useful to increase the Vitamin A content of cantaloupes, and thus a study was initiated to determine the genes (hereditary units on chromosomes) controlling Vitamin A content. If such genes could be identified and characterized, then plant breeders and geneticists could more effectively manipulate such genes to produce melons with enhanced amounts of Vitamin A through natural cross pollination (hybridization). The study allowed for the identification of genes on chromosomes and also provided information as to which genes were most important in the production of Vitamin A in melon fruit. Plant breeders and geneticists can use this information directly to increase the Vitamin A content of novel cultivars to improve human health of U.S. citizens. These improved cultivars will increase the marketability of U.S. melons, thus making the U.S. grower more competitive globally.

Technical Abstract: The nutritional value and yield potential of U.S. Western Shipping melon (Cucumis melo L.) could be improved through the introgression of genes for early fruit maturity (FM) and the enhancement of the quantity of B-carotene (QBC) in fruit mesocarp (i.e., orange mesocarp). Therefore, a set of 116 F3 families derived from the early FM Chinese line 'Q 3-2-2' (non-B-carotene content, white mesocarp) and the andromonecious, late FM U.S. Western Shipping (USWS) line 'Top Mark' (B-carotene content, orange mesocarp), were examined during two years in Wisconsin, USA to identify quantitative trait loci (QTL) assiciated with FM and QBC. A 171-point F2-3-based map was constructed and used for QTL analysis. Three QTL associated with QBC were detected which explained a significant portion of the observed phenotypic variation (R2 = 4.0 to 50.0%). The map position of one QTL (B-carM.E.9.1) was uniformly aligned with the carotenoid-related gene Or, suggesting its likely role in QBC in this melon population and putative relationship with melon white flesh (wf) gene. Two major (FM.6.1 and FM.11.1; R2 = >20%) and one minor QTL (FM.2.1; R2 = 8%) were found to be associated with FM. This map was then merged with a previous recombinant inbred line (RIL)-based map (256-point) used to identify seven QTL associated with the QBC in fruit. This consensus map [300 molecular markers (187 co-dominant melon and 14 interspecific)] provides a framework for the further dissection and cloning of published QTL, which will consequently lead to more effective trait introgression melon.