81
BH660 is the most popular maize hybrid in Ethiopia but is over 20 years old and
was not developed for drought tolerance. Between 2010 and 2012, annual certified
seed production of this variety peaked at 6000 tonnes—an amount sufficient to
cover more than 240,000 ha. Replacing the dominant but ageing crop varieties with
new climate-smart varieties is a critical step in reducing the risks of climate change
in SSA.
7.3 Research Efforts to Develop New Hybrids
The Ethiopian maize breeding programme was initiated in 1952 by first collecting
germplasm from various national and international sources (Tolessa et al. 1993).
The programme later focused on using germplasm of East African origin, owing to
agro-ecological similarity (Harrison 1970; Tolessa et al. 1993). BH660 was developed using early generation inbred lines (Harrison 1970; Tolessa et al. 1993; Ertiro
et al. 2015) derived from Kitale Synthetic II and ECU573. The current breeding
strategy is to exploit CIMMYT, International Institute of Tropical Agriculture, and
locally developed inbred lines—separately or in combination—to develop new DT
hybrids in Ethiopia.
Because of its wide cultivation and popularity, the replacement of BH660 with a
DT variety was considered crucial to address the increased frequency of drought as
a result of climate change in Ethiopia. The first approach was aimed at replacing
only the female parent of the single cross (SC) seed parent of BH660 with CIMMYT
DT inbred lines, and then replacing the third (male) parent with other ECU573derived inbred lines. This, however, was not successful as none of the hybrids outyielded the commercial checks. The second approach focused on a complete
replacement of the SC seed parent with a CIMMYT DT SC tester with excellent
general combining ability for drought stress, while maintaining the original male
parent. Over a period of 4 years (2006–2009), 9–12 hybrid combinations were
tested in more than 30 optimum and random drought environments (Table 7.1).
Among the tested hybrids, BH661 consistently outperformed the commercial
checks (BH660 and BH670) in most trial sites. In head-to-head comparison, BH661
showed an average grain-yield advantage (GYA) of 10.2% and 12.9% over BH660
and BH670, respectively. The new hybrid also showed an average of 2% reduction
in plant height, 6% reduction in ear placement and, crucially, 34% reduction in
lodging over BH660 (Fig. 7.1).
7.3.1 Release and Adoption of BH661
Unlike the established practice of embarking on variety demonstration only following official release, breeders conducted popularisation, demonstration and pilot
seed production concurrently with the variety verification trial of BH661. The variety verification trial is the final stage of variety evaluation in Ethiopia, whereby
7 Fast-Tracking the Development and Dissemination of a Drought-Tolerant Maize…
BH660 is the most popular maize hybrid in Ethiopia but is over 20 years old and
was not developed for drought tolerance. Between 2010 and 2012, annual certified
seed production of this variety peaked at 6000 tonnes—an amount sufficient to
cover more than 240,000 ha. Replacing the dominant but ageing crop varieties with
new climate-smart varieties is a critical step in reducing the risks of climate change
in SSA.
7.3 Research Efforts to Develop New Hybrids
The Ethiopian maize breeding programme was initiated in 1952 by first collecting
germplasm from various national and international sources (Tolessa et al. 1993).
The programme later focused on using germplasm of East African origin, owing to
agro-ecological similarity (Harrison 1970; Tolessa et al. 1993). BH660 was developed using early generation inbred lines (Harrison 1970; Tolessa et al. 1993; Ertiro
et al. 2015) derived from Kitale Synthetic II and ECU573. The current breeding
strategy is to exploit CIMMYT, International Institute of Tropical Agriculture, and
locally developed inbred lines—separately or in combination—to develop new DT
hybrids in Ethiopia.
Because of its wide cultivation and popularity, the replacement of BH660 with a
DT variety was considered crucial to address the increased frequency of drought as
a result of climate change in Ethiopia. The first approach was aimed at replacing
only the female parent of the single cross (SC) seed parent of BH660 with CIMMYT
DT inbred lines, and then replacing the third (male) parent with other ECU573derived inbred lines. This, however, was not successful as none of the hybrids outyielded the commercial checks. The second approach focused on a complete
replacement of the SC seed parent with a CIMMYT DT SC tester with excellent
general combining ability for drought stress, while maintaining the original male
parent. Over a period of 4 years (2006–2009), 9–12 hybrid combinations were
tested in more than 30 optimum and random drought environments (Table 7.1).
Among the tested hybrids, BH661 consistently outperformed the commercial
checks (BH660 and BH670) in most trial sites. In head-to-head comparison, BH661
showed an average grain-yield advantage (GYA) of 10.2% and 12.9% over BH660
and BH670, respectively. The new hybrid also showed an average of 2% reduction
in plant height, 6% reduction in ear placement and, crucially, 34% reduction in
lodging over BH660 (Fig. 7.1).
7.3.1 Release and Adoption of BH661
Unlike the established practice of embarking on variety demonstration only following official release, breeders conducted popularisation, demonstration and pilot
seed production concurrently with the variety verification trial of BH661. The variety verification trial is the final stage of variety evaluation in Ethiopia, whereby
7 Fast-Tracking the Development and Dissemination of a Drought-Tolerant Maize…