Asymmetric somatic hybridisation between the annual legumes Medicago truncatula and Medicago scutellata

 Interspecific asymmetric somatic hybrids have been produced between the sexually incompatible annual Medicago species Medicago truncatula and M. scutellata using only one regenerable parent and improved protoplast techniques. Regenerable M. truncatula leaf protoplasts were inactivated by lethal doses of iodoacetamide. Cotyledon protoplasts of non-regenerable M. scutellata were produced from 9 to 13 day old γ-irradiated cotyledons. Polyethylene glycol was used for protoplast fusion, and its successful use depended on a strategy to eliminate toxic effects. More than 50 mature regenerated plants were obtained from the fusion products and amplified fragment length polymorphism and chromosome analysis of a sample of 20 plants allowed the identification of two asymmetric hybrid plants. This technique is suitable for transferring characters from incompatible annual Medicago species to Medicago truncatula. Received: 23 July 1998 / Revision received: 21 December 1998 / Accepted: 15 January 1999