The Collaborative International Dictionary of English v.0.48:

Dysgenesis \Dys*gen"e*sis\, n. [Pref. dys- + genesis.] (Biol.)
   A condition of not generating or breeding freely;
   infertility; a form of homogenesis in which the hybrids are
   sterile among themselves, but are fertile with members of
   either parent race.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dysgenesis
    n 1: infertility between hybrids