RA 00110.pdf - OAR@ICRISAT

Discussion
Discussion following the paper on genetic diversity
in pearl millet covered reasons for the wide diversity
of African genetic resources (diverse climates and
agricultural systems); the maintenance and use of
that diversity by selfing, sibbing, and cluster bagging
(200 plant minimum); the widespread usefulness of
certain specific germplasm sources, and use of other
diversity that exists in wild relatives.
The performance of improved varieties under traditional
management in farmers' fields was the
primary topic following the paper on landrace
improvement. Evidence has shown no advantages to
new varieties under such conditions (compared to
trials using improved management), and it was concluded
that improvements in management would
have to accompany, or even precede, new varieties).
It was confirmed a reasonable objective to breed new
varieties which perform as well as traditional ones
under no-input management, but which respond
well to improved management.
After the paper on recurrent selection methods,
the discussion covered the choice of testers for use in
several reciprocal recurrent selection schemes in the
context of the theoretical and practical effects of
using elite or poor inbreds as testers. The role of
linkage blocks in the determination of actual gains in
response to recurrent selection which are not fully
accounted for in genetic models was discussed.
The discussion of the paper on hybrids in India
focused on the reasons for low adoption rates of
hybrids in stress environments. Adoption has been
high (85%) in Gujarat because of an intensive initial
extension effort, and the better performance of
hybrids in the drier areas, as well as in more favorable
climates. Lack of adoption elsewhere was considered
a result of insufficient education of the
farmers, insufficient seed supplies (but not the cost
of seed), and to the common necessity of resowing,
often several times.
Following the final paper dealing with breeding
male-sterile lines, the discussion dealt mainly with
the problem of downy mildew susceptibility. Early
male-steriles (and pollinators) were not thoroughly
tested for downy mildew resistance, but even though
5141A had been tested, it subsequently became susceptible.
Greater genetic diversity of male-sterile
lines was considered a necessity, but the greater
vulnerability of single-cross hybrids will probably
remain. India has a sufficiently large research,
extension, and seed production capability to exploit
hybrids, but the African countries of the Sahel do
not, and therefore the genetic stability of openpollinated
varieties may be preferable. There was
also discussion on whether the present classification
of male-sterile cytoplasm, which originated in the
1960s, is valid. Current evidence suggests a more
complicated picture.
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