Breeding
weevil-resistant maize: Is it feasible?
K. Pixley,
T. Dhliwayo & S. Munjoma
Maize weevil (Sitophilus
zeamais) causes extensive damage to stored maize (Zea mays), particularly to grain stored on-farm without chemical
protectants. Breeding of maize
varieties with improved weevil resistance, however, is not practiced to any
significant extent, because of uncertain probability of success and because
seed producers generally consider storability of grain to be outside of their
responsibility. The Rockefeller
Foundation-funded Weevil Project, at CIMMYT, has guided a total of four
graduate students through a progression of studies investigating the genetics
of weevil resistance and exploring practical methods for breeding maize with
increased resistance to weevil. Important
milestones within the five years of the project have been: 1) Identification
of significant genetic variation for weevil resistance among
regionally-adapted maize germplasm, 2) Investigations of secondary traits for
use in selecting maize with weevil resistance, 3) Successful divergent
selection for weevil resistance in several maize populations, and 4) Ongoing
investigations of per se resistance
relative to hybrid performance for maize lines at various levels of
inbreeding. This paper will
summarize recent results, describe on-going work, and offer recommendations
based on our current understanding of this important challenge. It is clear from results to date that breeding for improved
weevil resistance is possible; it remains unclear, however, what breeding
method(s), if any, are practical, effective and feasible for widespread use in
maize breeding programs.
