what test?

I have to compare several proteomic expression data of four different 
cultivar collected in two different year (4 x 2). what sort of 
statistical analysis have I to perform in your opinion?

This is a list for questions about R and teaching.  You would be
more likely to get an informative response from a more appropriate list.

Also, you should also describe your experiment in more detail.  What is the
scientific hypothesis you are interested in testing? 

For people who don't work on proteomic expression data, there would be
lots of basic questions (what's a cultivar?  are measurements from the
same cultivar in diffeent years independent, or correlated?  gaussian,
or counts, etc etc)

regards

albyn