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Description:
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The region of eastern and southern Africa is very diverse in environments and
agronomic practices . The region has one of the highest per capita consumption of maize (Zea
mays . L ) , which is predominantly produced by smallholder farmers . Some important constraints
facing these farmers include drought and low fertility . For decades , the International Center for
Wheat and Maize Improvement (CIMMYT ) has been involved in developing maize genotypes
that have high grain yields and are tolerant to drought , low fertility and other important
constraints . This germplasm is developed for wide adaptation . However , the development of
superior germplasm is significantly affected by interaction between genotypes and the
environment (i .e . , genotype by environment interaction , GEI ) . To estimate and understand GEI
maize genotypes are evaluated in a range of environments representing as much variability of the
target growing areas as possible . Because of dwindling resources needed to conduct testing in
the region , it may not be possible to test in all potential target areas . Therefore , a careful process
of site selection for testing is essential to improve efficiencies in cultivar testing and deployment .
The objective of this research was to characterize the maize testing locations of the
eastern and southern Africa region . Historical data from CIMMYT Regional Trials from 1999 to
2003 was used to characterize the environments and estimate genetic parameters .
Environmnent and GEI showed consistently high contributions to the total variation
observed among genotypes for grain yield . Environment contributed over 60 % and sometimes
up to 85 % of total variation observed . Sequential retrospective pattern analysis (Seqret ) was
conducted on the adjusted standardized grain yield .
A total of 7 groups of environments were identified . Repeatabilites , a measure of the
proportion of phenotypic variation that is due to genetic differences , was reduced under stress
conditions . The relationship among traits showed that anthesis -silking interval (ASI ) is an
important selective trait , which can improve selection efficiency for grain yield under stress conditions . Stability analysis provided an opportunity to observe the response and adaptation of
genotypes to a wide range of environments . Variety ZM621 was a stable and high yielding
genotype . |