  Motivated by the relationship between numerical Grothendieck groups induced
by the embedding of a smooth anticanonical elliptic curve into a del Pezzo
surface, we define the notion of a quasi del Pezzo homomorphism between
pseudolattices and establish its basic properties. The primary aim of the paper
is then to prove a classification theorem for quasi del Pezzo homomorphisms,
using a pseudolattice variant of the minimal model program. Finally, this
result is applied to the classification of a certain class of genus one
Lefschetz fibrations over discs.
