Plant regeneration after long-term callus culture in clones of Asparagus officinalis L.

Callus growth and plant regeneration from long-term callus cultures were studied in two elite clones of Asparagus officinalis cv. Argenteuil, to establish a suitable protocol for a prospective in vitro selection program. Callus initiation and growth was evaluated on MS medium with 3% sucrose, 0.9% agar, 1 mg x l(-1) kinetin, and three levels of 2,4-D. The highest callus relative growth was obtained on medium with 1.5 mg x l(-1) 2,4-D and 1 mg x l(-1) kinetin. Shoot primordia (SP) induction from > 18-months-old calluses was evaluated on several media; the highest percentage of SP induction (89%) and average number of SP per callus (8.6) were obtained with clone "265" on MS medium with 5 mg x l(-1) 2iP, 1 mg x l(-1) IAA, 3% sucrose and 0.9% agar. The highest percentage of root induction (100%) was achieved with clone '265' on MS medium with 0.1 mg x l(-1) kinetin, 0.1 mg x l(-1) NAA, 1.32 mg x l(-1) ancymidol, 7% glucose and 0.8% agar. Important medium x genotype interactions were detected, pointing to the need of adjusting this and other in vitro protocols for specific asparagus genotypes.