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used to develop improved varieties in a cost-
effective manner? Major challenges constraining
adoption include lack of capacity in the use of
these tools, motivation on the part of breeders to
learn these technologies and then make the nec-
essary changes in the general workflow and cost
structure of their breeding programs to accom-
modate MAB activities, and realizing a favor-
able cost/benefit ratio compared to conventional
breeding. Part of achieving cost-effectiveness
will be to develop breeding strategies that min-
imize the amount of genotyping while maxi-
mizing overall marker information. Almost all
cowpea breeding programs worldwide are pub-
lic enterprises. Thus, the question arises as to
who will absorb the costs of capacity building
and, in some cases, infrastructure development
for these efforts. With the increased potential of
MAB there are costs beyond those for genotyp-
ing. These include learning costs for the imple-
mentation of new breeding plans and methods.
More detailed planning and logistics are needed,
as well as new ways of operating, greater design
complexity, including knowledge about genotyp-
ing, marker-trait association, marker platforms,
and a several-fold increase in the amount of
genotypic and phenotypic data that need to be
managed effectively. Training in modern cow-
pea breeding must be a key future activity, since
so few breeders are prepared now to utilize effec-
tively all the new tools of modern breeding. Cow-
pea breeders have developed a number of culti-
vars with 'stacked' resistance for traits such as
resistance to cowpea weevil, cowpea aphid, and
Striga, along with resistances to bacterial blight,
CABMV, and other pathogens. The challenge is
to incorporate all of these desirable traits into
individual cultivars with acceptable grain qual-
ity and adaptation to a diverse array of farming
systems and environments. MAB can be a key
enabling tool to realize this goal.
breeding as well as with conventional breed-
ing. Inaccurate or failed phenotyping negatively
impacts modern breeding programs more than
conventional breeding programs, in that poor
phenotyping outcomes consume resources in
generating genotypic information that cannot be
used effectively. SNP genotyping of cowpea is
now straightforward and, from a technical stand-
point, virtually error-free. For nearly all traits,
phenotyping is, by comparison, much more dif-
ficult. Yet each process must be conducted with
a level of precision adequate to capitalize on
the information content of the other for modern
breeding to be efficient and effective. Therefore,
breeders must make the necessary infrastructure
and time investments in phenotyping capability
to ensure a correct balance consistent with the
goals of the breeding program.
Improved phenotyping capability is needed
in conventional as well as modern breeding pro-
grams, but the way in which it is applied may dif-
fer in the different types of breeding programs.
A comprehensive review of classical cowpea
breeding and phenotyping for critical biotic and
abiotic production constraints that is still relevant
was published by Hall and colleagues in 1997.
New or modified protocols have been published
more recently for phenotyping for resistance to
bacterial blight (Agbicodo et al. 2010), rust (Li
et al. 2007), ashy-stem blight (Muchero et al.
2011), and foliar thrips (Muchero et al. 2010).
MAS for Pyramiding Multiple Pest and
Disease Resistance Traits
One of the major goals of most cowpea breeding
programs is to combine resistances to numer-
ous pests and diseases and other desirable traits
such as those governing maturity, photoperiod
sensitivity, plant type, and seed quality. Until
recently these programs have lacked modern
breeding tools and an array of elite parental lines
that are fixed for most of the desired resistance
factors. The elite lines can be used to recom-
bine traits and generate lines with multiple pest
and disease resistance, high yield, appropriate
Phenotyping
Accurate phenotyping for biotic stress resistance
or tolerance is central to success with modern
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