The influence of ethyl methanesulfonate (EMS) and N-nitrose-N´-ethyl urea (ENU) mutagenic treatments was investigated on three time sub-cultured calli and on regenerating shoots coming from roots and leaf petiole explants of 7-day old sterile plants respectively. Calibrated sterile seeds of Bulgarian the common bean variety “Plovdiv 11M” were precultivated on MS basal medium supplemented with 1 μM BAP. Different concentrations of mutagens (2.5 . 10-2, 1.25 . 10-2, 6.2 . 10-3 M for EMS, and 6.2 . 10-3, 3.1 . 10-3, 1.55 . 10-3 M for ENU) were applied for 60 min to the treated explants.
Mutagenic concentrations influenced both the callus growth and regeneration, these increasing at the lowest concentrations. ENU showed a stronger effect than EMS in both processes, while the lowest EMS concentrations (6,2·10-3 M) stimulated significantly shoot formation and plant regeneration.
Morphological and chlorophyll changes (chlorina and viridissima types) in shoots and regenerates were found but whole plants did not develop from them. The effect of subcultures on callus growth was higher than that of mutagenic treatments. Interactions between these factors were quite low.