Plant & Animal Genome IX Conference

Poster: Sequencing & EST
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EST DEVELOPMENT IN SWEETPOTATO FROM cDNA LIBRARIES OF PENCIL AND STORAGE ROOTS

¹ Potato Research Centre, Agriculture and Agri-Food Canada, P.O. Box 20280, 850 Lincoln Road, Fredericton, New Brunswick, E3B 4Z7 CANADA

² International Potato Center, P.O. Box 1558, Lima 12, Peru

Sweet potato [Ipomoea batatas (L.) Lam.] is the seventh most important food crop in the world. It is well recognized that this crop has a great potential to contribute to the improvement of food security in the developing countries. There is large variation of dry matter content in the sweetpotato germplasm, ranging from 18-44%. Starch is the predominant carbon sink of the storage roots. The ability to synthesize starch in the sink may play a central role in the control of the storage root development and photosynthate partitioning. Our objective is to identify genes involved in the process of starch synthesis; the storage roots initiation, enlargement, and the partitioning of assimilate in sweetpotato. Two cDNA libraries using mRNAs from differentiated pencil and storage roots of a high starch Japanese breeding line Kyukei No. 63 have been constructed in the lambda Uni-ZAP XR vector. A portion of the libraries was used for in vitro excision to generate pBluescript SK- phagemid clones for sequencing. BLAST search using the first set of ESTs (expressed sequence tags) has identified several putative candidate genes involved in carbohydrate metabolism and storage root development. These selected ESTs will also be located to the sweetpotato genetic map using a population segregating for dry matter content. Differential expression and map coincidence with QTL for dry matter will provide good evidence that such candidate ESTs belong to key genes for starch synthesis and storage root development.