Light quality regulates shoot cluster growth and development of MM106 apple genotype in in vitro culture

The interaction between shoot proliferation and regulative action of light quality was investigated in terms of cluster growth and development. In the commercial laboratory, the shoot multiplication procedure is normally conducted by growing clusters of shoots during several sub-cultures. Thus in this work the regulative action of light quality was evaluated by analysing the shoot cluster proliferation rate, the evolution of axillary bud differentiation, the axillary shoot development on both initial explant stem (order 1 axis) and three representative lateral branches (order 2 axes), growing from the lateral buds located at the bottom of the initial explant. Experiments showed that light qualities regulate bud differentiation and interact with apical dominance, leading to strong control of axillary bud outgrowth, and, finally, resulting in a differentiated architectural formation of clusters and type of branching.