POTENTIAL OF SOMATIC EMBRYOGENESIS IN PRUNUS-AVIUM IMMATURE ZYGOTIC EMBRYOS

For the purpose of developing somatic embryogenesis in Prunus avium L., immature zygotic embryos, collected from five donor trees and sorted into two size classes (C1: 2.5-3.5 and C2: 3.6-4.5 mm), received various experimental treatments. When cultured for 10 days on an inductive medium containing 18.1 muM 2,4-dichlorophenoxyacetic acid (2,4-D) and 9.3 muM kinetin, then transferred to fresh medium without growth regulators, 2.5% of the Cl class cotyledons expressed direct somatic embryogenesis. C2 class cotyledons were less responsive. The response was also influenced by the chosen donor tree. In a few cases, spontaneous germination occurred. The presence of a root meristem was clearly demonstrated by histological examination of longitudinal sections. The replacement of half the amount of 2,4-D, present in the inductive medium mentioned above, by the same quantity of naphthaleneacetic acid reduced the incidence of somatic embryogenesis. Conversely, a rhizogenic response was strongly enhanced. When submitted to an inductive medium containing indoleacetic acid and zeatin without any subcultures for 3 months, C1 class cotyledons were the most morphogenic and developed leaves and cotyledon-like structures.