A faba bean line showing a high degree of resistance was
identified by Egyptian scientists early in the 1970s (Nassib
et al. 1982) and subsequently confirmed in laboratory and
field experiments. Further resistance studies in faba bean
have revealed a purely quantitative genetic system with strong
additive and very weak dominance effects (Cubero 1983).
Improvement of crop species for quantitative traits is difficult
because the effects on individual genes controlling the
traits cannot be readily identified