Production of somatic hybrid plants between Japanese bunching onion (Allium fistulosum L.) and bulb onion (A. cepa L.) via electrofusion

Abstract

Interspecific somatic hybrids between Japanese bunching onion (Allium fistulosum L., 2n=2x=16) and bulb onion (A. cepa L., 2n=2x=16) were produced by the electorofusion of protoplasts. A concentration of iodoacetamide (IOA), suitable for inhibiting the formation of colonies from protoplasts in Japanese bunching onion, was used. IOA-treated protoplasts of Japanese bunching onion and untreated protoplasts of bulb onion were mixed together and fused, with the expectation that only heterokaryons would selectively develop into colonies. Four hundred and seventeen colonies had formed from fusion products after a 45- day culture, of which approximately 80% developed into calli. Plant regeneration was achieved in 33 out of 325 (10.1%) calli. Some regenerants expressed abnormalities, but two were successfully transplanted in a greenhouse. Cytogenetical and DNA analyses revealed these two regenerants to be amphidiploids (2n=4x=32). Furthermore, it was shown that another three regenerants possessed the nuclear genome of Japanese bunching onion, whereas, their chloroplasts were from bulb onion. The application of these hybrids to a breeding program for Japanese bunching onion is discussed.