Production of Somatic Hybrid between Cultivars of Sweet Potato, Ipomoea batatas(L.) Lam. in the Same Cross-incompatible Group.

Abstract

This is the first report on successful production of somatic hybrid between cross-incompatible cultivars of sweet potato, lpomoea batatas (L.) Lam. The protoplasts of sweet potato cultivars, Koganesengan and Bitambi, belonging to the same cross-incompatible B group and not crossing with each other, were fused with Polyethylene Glycol (PEG) solution and then cultured in modified liquid MS (Murashige and Skoog 1962) medium containing 0.05 mg/l 2, 4-dichlorophenoxyacetic acid (2, 4-D) and 0.5 mg/l kinetin. Forty-five plants were obtained from the calli on the hormone-free medium by using the callus proliferation medium either supplemented with 2, 4-D and kinetin or abscisic acid (ABA), or supplemented with naphthalene aceic acid (NAA) and 6-benzylaminopurine (BAP). Two plants were considered to be the somatic hybrids by analyzing their morphology, chromosome numbers and random amplified polymorphic DNA (RAPD) markers. The hybrids showed intermediate characters in leaf shape and leaf color between the two parents and had chromosome numbers that correspond to the sum of their parents (2n= 12x (2n+2n)= 180). By RAPD assay, they expressed some of the bands from both parents. They grew slowly in the field. One of them had the pollen fertility of 12.2 % when grafted on the morning-glory for flower induction. No seed was obtained by crossing with pollen of Kyushu No. 30 (cross-incompatible C group cultivar).