Sweet potato [Ipomoea batatas] is the world's seventh largest food crop cultivated worldwide due to its high yield, rich nutrition and strong resistance. Based on the integrated transcriptome database represented by 3 cultivars in China, totally 238 transcripts related to drought- and salt-tolerance were obtained, of which 9 transcripts with full-length open reading frame were selected randomly for cloning and sequencing. The similarity between assembled and cloned sequences was higher than 98%, demonstrating that the assembled transcripts are reliability. Moreover, the expression levels of these resistant genes among cultivars were analyzed and the results showed that the expressions of drought-tolerant genes were generally high in Jingshu 6 and relatively low in Xushu18, while the salt-tolerant genes had opposite expression patterns. The digital gene expression profiling was also used for analyzing these gene expressions among six tissues and development stages of Xushu18. The results displayed that these resistant genes had relatively high-expression levels in mature leaves and expanding tuberous roots. The results from q-RT PCR verified the differential expression patterns of genes detected in the digital gene expression profiling.
