Micropropagation of Ulmus minor and U. minor x U. pumila from 4-year-old ramets

Abstract

As part of the Spanish breeding programme against Dutch elm disease, investigations were undertaken on reproduction of Ulmus minor by means of tissue culture. Microshoots were obtained from nodal segments, collected from terminal twigs of 4-year-old ramets of selected clones of this species and of U. minor x U. pumila, and cultured on a modified Murashige & Skoog medium containing 6-Benzylaminopurine (BA). When subcultured, the microshoots or nodal segments excised from these, formed new shoots, their maximum numbers per explant (1.94 to 2) being obtained with the hybrid clone M-TC2 on media containing 3.5 to 8.8 μM BA. The number of microshoots obtained was highest with subcultures of the whole shoot, e.g. 6.9 times superior to control, against 1.5 with nodal segments of VJR1 in presence of 8.8 μM BA. The addition of 0.5 to 5.3 μM indole-acetic acid of α-naphthaleneacetic acid to the medium induced the highest percentage of root formation from the shoots. Both shoot and root formation varied greatly among clones.