Studies On The Production Of Interspecific Hybrids Of Ipomoea Section Batatas By Somatic Hybridization

Sweetpotato (Ipomoea batatas (L.) Lam.) and its related species are called plants of Ipomoea section batatas, which are classified into two groups based on the cross-compatibility with sweetpotato: Group I cross-compatible with sweetpotato and Group II cross-incompatible with sweetpotato. Most of the related species belong to Group II. I. triloba of Group II possesses some potential useful genes of drought-tolerance, and root rot and other fungous disease resistance. It can grow under the condition of extreme drought and absolute wetness. However, I. triloba has not been successfully utilized in sweetpotato breeding due to the cross-incompatibility with sweetpotato. In this study, the interspecific cross-incompatibility between sweetpotato and I. triloba was successfully overcome by somatic hybridization, and the hybrids were obtained in two combinations of Lizixiang and I. triloba, Nongdahong and I. triloba, which laid a strong foundation for the further exploitation of useful genes of I. triloba. The somatic hybrids were transplanted to the fields to explore the usefulness in sweetpotato breeding by observing and evaluating the upper-ground and under-ground traits. The results were as follows:1. Embryogenic calli were induced from the shoot tips of sweetpotato cvs. Lizixiang and Nongdahong. Embryogenic suspension cultures of these two cultivars were established. Such embryogenic suspension cultures provided the ideal material for somatic hybridization of sweetpotato.2. Protoplasts isolated from embryogenic suspension cultures of sweetpotato cvs. Lizixiang and Nongdahong were fused with petiole protoplasts of I. triloba by PEG method. Interspecific somatic hybrids were obtained from the fused products. Twenty-four of the 33 regenerated plants from the fused products of Lizixiang and I. triloba, 132 from Nongdahong and I. triloba were proved to be somatic hybrids by cytological observation, peroxidase isozymes and random amplified polymorphic DNA (RAPD) analyses.3. Some interspecific somatic hybrid plants were transplanted to the fields to observe the upper-guound and under-ground traits. Most of the hybrids showed a weak growth vigor and a part of the hybrids had the phenomena of physiological atrophy or death. But a small number of the hybrids showed the good growth potential. The leaf shape and plant type of the hybrids were the middle of two parents. Up to date, no hybrids were found to form thickened roots.