Ploidy level and molecular phylogenic relationship among novel Ipomoea interspecific hybrids

Interspecific hybridization can be used to broaden the genetic base, generate novel species, postulate genetic relationships, and to introgress elite alien genes. However, interspecific hybridizations using wild parents outside the Ipomoea section Batatas are very difficult and have not been much studied. We used an improved hybridization technology to generate three novel interspecific hybrids by crossing Ipomoea batatas (L.) Lam. × I. hederacea Jacq., I. batatas (L.) Lam. × I. muricata (L.) Jacq., and I. batatas (L.) Lam. × I. lonchophylla J.M. Black. The ploidy level of the interspecific hybrids was determined by flow cytometry. The cross, I. batatas × I. hederacea, yielded the first artificial pentaploid Ipomoea hybrid ever. The other two hybrids, I. batatas × I. hederacea and I. batatas × I. muricata were tetraploid. The first two hybrids showed normal storage roots, a significant improvement in the storage roots of currently existing interspecific Ipomoea hybrids. AFLP (Amplified Fragment Length Polymorphism) molecular markers were used to explore the genetic relationship of these three novel interspecific hybrids with three other natural diploid, tetraploid, and hexaploid species of the Ipomoea section Batatas. Cluster analysis of AFLP bands showed that these three new interspecific hybrids were closely related to cultivated sweet potato (I. batatas/L./Lam.), which indicated that these novel hybrids can be used as an interspecific bridge to transfer alien genes from wild to cultivated species.