Identifying  core genes  is important  to understand  evolutionary and
functional phylogenies. Therefore, in  this work we present methods to
build a genes  content evolutionary tree. More precisely,  we focus on
the following  questions considering a  collection of 99~chloroplasts
annotated from NCBI \cite{Sayers01012011} and Dogma \cite{RDogma}: how
can  we identify the  best core  genome and  what is  the evolutionary
scenario of these chloroplasts.
