Abstract
Haploid breeding via in vivo induction of maternal haploids is rapidly replacing the pedigree breeding methods since it reduces the breeding cycle from at least 6 to 1-2 generations to reach a homozygous state. Eighty doubled haploid (DH) lines derived from nine tropical maize backcross populations were crossed to two CIMMYT single cross testers (CML312/CML442 and CML395/CML444) in a North Carolina II mating design. The resultant 160 DH testcross hybrids and five commercial checks were evaluated across four well-watered locations and two drought stressed locations in Kenya using an alpha-lattice design of 15 x 11 replicated twice. Significant differences (0.05 < p < 0.001) were observed in location, genotype and genotype by environment interaction for grain yield, days to anthesis, anthesis-silking interval and ear aspect under nonstress conditions. Combined analyses across drought stress and well-watered environments showed that the top 20 hybrids performed better for grain yield and other agronomic traits of maize compared to the commercial checks. Grain yield for the top 20 DH hybrids ranged from 8.15-8.85 t/ha under optimum management and 4.53-5.67 t/ha under drought stress conditions while the best commercial variety yielded 7.67 t/ha and 3.43 t/ha under optimum and drought stress conditions, respectively. The top ten DH testcross hybrids averaged over the four optimum locations yielded 16% higher than the best commercial check while under managed drought the top ten DH hybrids produced 62% higher grain yield than the best commercial check. Three DH testcross hybrids entries 23, 28 and 71 performed highly for grain yield under both stress and non-stress locations high stress tolerance indices (STI) and low stress susceptibility indices (SSI). These results indicated that maize hybrids developed from DH lines produced as high a grain yield and as acceptable agronomic traits as the commercial hybrids developed through conventional pedigree methods. The DH lines identified in the study should be useful in improving grain yields and in the drought prone mid-altitude areas of eastern and southern Africa.
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Claims 12
Claim · model-written summary
Location, genotype and genotype by environment interaction differed significantly for grain yield, days to anthesis, anthesis-silking interval and ear aspect under nonstress conditions.
- Outcome
- grain yield, days to anthesis, anthesis-silking interval and ear aspecte0
- Setting
- nonstress conditionse0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant differences (0.05 < p < 0.001) were observed in location, genotype and genotype by environment interaction for grain yield, days to anthesis, anthesis-silking interval and ear aspect under nonstress conditions”
e1“agronomic traits of maize”
Claim · model-written summary
The top 20 maize hybrids performed better for grain yield and other agronomic traits than commercial checks across drought and well-watered environments.
- Material
- top 20 hybridse0
- Treatment
- drought stress and well-watered environmentse0
- Outcome
- grain yield and other agronomic traitse0
- Direction
- bettere0
- Comparator
- commercial checkse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Combined analyses across drought stress and well-watered environments showed that the top 20 hybrids performed better for grain yield and other agronomic traits of maize compared to the commercial checks”
Claim · model-written summary
Top 20 DH maize hybrids yielded 8.15-8.85 t/ha under optimum management.
- Material
- top 20 DH hybridse0
- Outcome
- Grain yielde0
- Direction
- rangede0
- Value
- 8.15-8.85 t/hae0
- Setting
- under optimum managemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yield for the top 20 DH hybrids ranged from 8.15-8.85 t/ha under optimum management”
e1“agronomic traits of maize”
Claim · model-written summary
Top 20 DH maize hybrids yielded 4.53-5.67 t/ha under drought stress.
- Material
- top 20 DH hybridse0
- Outcome
- Grain yielde0
- Direction
- rangede0
- Value
- 4.53-5.67 t/hae0
- Setting
- under drought stress conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yield for the top 20 DH hybrids ranged from 8.15-8.85 t/ha under optimum management and 4.53-5.67 t/ha under drought stress conditions”
e1“agronomic traits of maize”
Claim · model-written summary
The best commercial maize variety yielded 7.67 t/ha under optimum conditions.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the best commercial variety yielded 7.67 t/ha and 3.43 t/ha under optimum and drought stress conditions, respectively”
e1“agronomic traits of maize”
Claim · model-written summary
The best commercial maize variety yielded 3.43 t/ha under drought stress.
- Material
- the best commercial varietye0
- Outcome
- yieldede0
- Value
- 3.43 t/hae0
- Setting
- drought stress conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the best commercial variety yielded 7.67 t/ha and 3.43 t/ha under optimum and drought stress conditions, respectively”
e1“agronomic traits of maize”
Claim · model-written summary
Top ten DH maize testcross hybrids yielded 16% more than the best commercial check across four optimum locations.
- Material
- top ten DH testcross hybridse0
- Treatment
- four optimum locationse0
- Outcome
- yieldede0
- Direction
- highere0
- Value
- 16%e0
- Comparator
- best commercial checke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The top ten DH testcross hybrids averaged over the four optimum locations yielded 16% higher than the best commercial check”
e1“agronomic traits of maize”
Claim · model-written summary
Top ten DH maize hybrids produced 62% higher grain yield than the best commercial check under managed drought.
- Material
- top ten DH hybridse0
- Treatment
- managed droughte0
- Outcome
- grain yielde0
- Direction
- highere0
- Value
- 62%e0
- Comparator
- best commercial checke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under managed drought the top ten DH hybrids produced 62% higher grain yield than the best commercial check”
e1“agronomic traits of maize”
Claim · model-written summary
DH maize testcross entries 23, 28 and 71 had high grain yield under both stress and non-stress conditions.
- Material
- entries 23, 28 and 71e0
- Outcome
- grain yielde0
- Direction
- highlye0
- Setting
- both stress and non-stress locationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Three DH testcross hybrids entries 23, 28 and 71 performed highly for grain yield under both stress and non-stress locations”
e1“agronomic traits of maize”
Claim · model-written summary
DH maize testcross entries 23, 28 and 71 had high stress tolerance indices.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Three DH testcross hybrids entries 23, 28 and 71 performed highly for grain yield under both stress and non-stress locations high stress tolerance indices (STI)”
e1“agronomic traits of maize”
Claim · model-written summary
DH maize testcross entries 23, 28 and 71 had low stress susceptibility indices.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Three DH testcross hybrids entries 23, 28 and 71 performed highly for grain yield under both stress and non-stress locations high stress tolerance indices (STI) and low stress susceptibility indices (SSI)”
e1“agronomic traits of maize”
Claim · model-written summary
The identified DH maize lines are proposed for improving grain yields in drought-prone mid-altitude areas of eastern and southern Africa.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The DH lines identified in the study should be useful in improving grain yields and in the drought prone mid-altitude areas of eastern and southern Africa”
e1“agronomic traits of maize”
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