you have only one material number, and this is the material number of the material that you want extend. A direct input program works much different to a user transaction. you are writing entries directly into a table, just minimal checks from SAP, you have to secure that you move all field values and that all field values are consistent and valid.
Why should the MARA field be copied? they are already present, MARA is only there once.
if you only extend then you do not need to consider the basic data view (BMMH0-XEIK1 = ' ')