Cactus / Astrophytum hybrid

This is 1st filial Astrophytum hybrid, capricorn v niveum x asterias cv super kabuto.
I sowed seeds on 28/08/2010.
The success ratio of germination was not too bad but the growing speed of seedlings were extremely slow. I think this problem is affected by hybridization of different flower colors.
I grafted 1 seedling last summer.
The scion has started to grow as shown on the attached photo.
The scion is variegated becuse of hybridization stress.