Production and characterization of a novel interspecific somatic hybrid combining drought tolerance and high quality of sweet potato and Ipomoea triloba L.

A novel interspecific somatic hybrid combining drought tolerance and high quality of sweet potato and Ipomoea triloba L. was obtained and its genetic and epigenetic variations were studied. Somatic hybridization can be used to overcome the cross-incompatibility between sweet potato (Ipomoea batatas (L.) Lam.) and its wild relatives and transfer useful and desirable genes from wild relatives to cultivated plants. However, most of the interspecific somatic hybrids obtained to date cannot produce storage roots and do not exhibit agronomic characters. In the present study, a novel interspecific somatic hybrid, named XT1, was obtained through protoplast fusion between sweet potato cv. Xushu 18 and its wild relative I. triloba. This somatic hybrid produced storage roots and exhibited significantly higher drought tolerance and quality compared with its cultivated parent Xushu 18. Transcriptome and real-time quantitative PCR (qRT-PCR) analyses revealed that the well-known drought stress-responsive genes in XT1 and I. triloba were significantly up-regulated under drought stress. The genomic structural reconstructions between the two genomes of the fusion parents in XT1 were confirmed using genomic in situ hybridization (GISH) and specific nuclear and cytoplasmic DNA markers. The DNA methylation variations were characterized by methylation-sensitive amplified polymorphism (MSAP). This study not only reveals the significance of somatic hybridization in the genetic improvement of sweet potato but also provides valuable materials and knowledge for further investigating the mechanism of storage root formation in sweet potato.