Gains in maize genetic improvement in Eastern and Southern Africa : II. CIMMYT open-pollinated variety breeding pipeline
2017
Open-pollinated varieties (OPVs) still represent
a significant proportion of the maize (Zea mays
L.) seed system in many countries of sub-
Saharan Africa. The International Maize and
Wheat Improvement Centre (CIMMYT) has
been breeding improved maize varieties for the
stress-prone environments experienced by most
smallholder farmers in eastern and southern
Africa for over 30 yr. Hybrid breeding is now the
major focus of the CIMMYT breeding pipeline.
However, OPVs are generated within the hybrid
pipeline. This is the first study to document
genetic gain for maize grain yield under both
optimal and stress (random and managed
drought, low nitrogen [N], and maize streak virus
[MSV]) conditions within the CIMMYT eastern
and southern African OPV breeding pipeline.
Genetic gain was estimated using the slope of
the regression on the year of OPV release in
regional trials over a 12-yr period (1999–2011).
Open-pollinated varieties were separated into
two maturity groups, early (<70 d to anthesis)
and intermediate-late (>70 d to anthesis).
Genetic gain in the early maturity group under
optimal conditions, random drought, low N, and
MSV was 109.9, 29.2, 84.8, and 192.9 kg ha−1
yr−1. In the intermediate-late maturity group,
genetic gain under optimal conditions, random
drought, low N, and MSV was 79.1, 42.3, 53.0
and 108.7 kg ha−1 yr−1. No significant yield gains
were made under managed drought stress
for both maturity groups. Our results show
continued improvement in OPVs for both yield
potential and stress tolerance.
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