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Genetics
Genetics
Pages 57-63
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From page 57... ...
However, from the beginning researchers observed that, although most opaque-2 kernels are soft and chalky, a few ears have odd kernels that are partially transparent. They also noticed other rare kernels with islands or bands of hard endosperm.
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From page 58... ...
This is perhaps a more realistic process, but the ability in the early stages to remove portions so tiny that the seeds remained viable was the critical key to success. In this way, by 1974 CIMMYT had developed four basic donor stocks that were broadly adapted to typical agroclimatic zones.
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From page 59... ...
In the stress trials, each was evaluated for its ability to withstand diseases, insects, and highdensity planting. Specifically, families in the disease nursery were rated for their response to stalk rots and ear rots (under artificial inoculation)
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From page 60... ...
But when the breeding first began accumulating hard endosperm, the ears of many genotypes developed gaps between the kernel rows. Consequently, CIMMYT researchers later selected ears with less and less inter-row space, until ears filled with normal-sized kernels and near-normal numbers were obtained.
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From page 61... ...
Local checks were the best yielding local variety of common maize. The figure shows that in results from two 1983 experimental trials, QPM performed as well as (and sometimes better than)
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From page 62... ...
FUNGAL INFECTIONS The higher incidence of fungal ear rots in opaque-2 maize results, at least in part, from its soft kernels and higher moisture content. Hardening the kernels automatically reduced the incidence of ear rot.
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From page 63... ...
GENETIC INSIGHTS CIMMYT has demonstrated that significant progress in overcoming undesirable effects of otherwise desirable single genes can be made through the use of gene modifiers. The extent to which this is applicable to other species and other problems is as yet unknown.
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