RA 00110.pdf - OAR@ICRISAT

S h o r t - t e r m g o a l s
I n t e r m e d i a t e range g o a l s
Long-range g o a l s
Time
Figure 1. Three populations and their expected response patterns.
genetic variation is increased. In practice compromise
is necessary. The Nebraska hybrids are very different
in breadth of adaptation: some must be grown
under very specific conditions or in only certain
areas, while others may be very broadly adapted (for
instance, the maize hybrid B73 x Mo17 has been
grown all over the world). Admittedly not much is
known about this problem because it is apparently
complex. It seems prudent that a breeder restrict the
target set of environments to a logical subset among
which G * E interaction is not too large. For maize,
Nebraska is divided into three zones that form a
logical grouping (Figure 2). Western Nebraska (Zones
I and II) requires earlier maize varieties than the
eastern portion, so population improvement is done
within these zones.
not a major problem except for the difficulty of
handling missing plots. The two analyses of variance
with and without replication at each location are
shown in Table 3. Note that the appropriate test of
significance for entries is present even without replication
at each location, assuming that locations are
random. Thus a broader array of macroenviron-
Zone I
Zone I I
Sampling Environments
Zone
I I I
To sample environments within a subset, families
may be tested with only one replication in each
location when seed quantities are restricted. This is
Figure 2. Corn-growing zones in the state of Nebraska
in the central part of U S A .
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