Genetic analysis of variation in micropropagated plants of Melia azedarach L.

Plants were regenerated by shoot multiplication from four clones of Melia azedarach L. during 12 mo. of subculturing. One hundred and one of these plants were examined by randomly amplified polymorphic DNA analysis. All regenerated plants showed at least one polymorphism. However, no chromosome number alterations were observed. The pattern of variation obtained by principal coordinated analysis showed a random distribution of variation among regenerated plants and their controls, indicating that genetic alterations were not cumulative during in vitro culture. Similar results were found using Shannon's index, which revealed that 50% of the observed diversity resided among plants coming from the same subculture generation. This high intraclonal variation does not provide a clear scenario for predicting the amount of culture time required to preserve genetic fidelity in commercially micropropagated M. azedarach plants. Our work suggests that other mechanisms, such as chimerism, contribute to intraclonal heterogeneity in vitro.