Abstract
SUMMARY The use of secondary traits such as number of ears per plant, grains per ear, the interval from anthesis to silking, leaf senescence and leaf rolling, together with management of water stress and recurrent selection, have permitted a considerable increase in drought tolerance in the CIMMYT maize source germplasm populations Drought Tolerant Population (DTP) and La Posta Sequía (LPS). Inbred lines were extracted from DTP C 9 and LPS C 7 cycles and then used for generating single and three-ways hybrids. These were evaluated under normal irrigation and managed drought conditions. A weak, and in some cases no longer significant, correlation was found between grain yield and the traits initially used for selection. Most prominently, the relationship between anthesis-silking interval and grain yield became much weaker in these hybrids. Conversely, significant negative correlations were found between tassel dry weight and grain yield. Three-way hybrids involving two DTP lines yielded more than those involving one only, indicating the feasibility of gene pyramiding for drought tolerance. Overall, the results suggested that the relationship between grain yield and secondary traits has been modified due to continuous selection in the LPS and DTP populations. Some long-established secondary traits have become less important, while others have become more relevant. Mean grain weight, previously not used within a drought selection index, was strongly correlated with yield in the present study. The importance of traits related to the availability in C products for the development of ears and grains are discussed. The results indicate that the traits of source organs contribute marginally to drought tolerance; variation of leaf or root traits seems to be less important than variation in tassel parameters for increasing drought tolerance. For ensuring further progress in drought tolerance in maize, the solution might reside in the manipulation of sink organs. It is therefore suggested that selection for even greater number of ears, bigger grains and smaller tassels may help to increase grain yield under water limited environments in the near future. A short discussion on the optimal choice of parental lines for developing hybrids with maximum expression of drought tolerance concludes the paper.
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Claims 11
Claim · model-written summary
The correlation between grain yield and the traits initially used for selection was weak and in some cases no longer significant.
- Outcome
- grain yielde1
- Qualifier
- in some cases no longer significante1
- Comparator
- the traits initially used for selectione1
Zea maysNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e1“A weak, and in some cases no longer significant, correlation was found between grain yield and the traits initially used for selection”
Claim · model-written summary
The relationship between anthesis-silking interval and grain yield became much weaker in the hybrids evaluated under managed drought.
- Outcome
- relationship between anthesis-silking interval and grain yielde2
- Direction
- much weakere2
- Setting
- managed drought conditionse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e1“These were evaluated under normal irrigation and managed drought conditions”
e2“Most prominently, the relationship between anthesis-silking interval and grain yield became much weaker in these hybrids”
Claim · model-written summary
Tassel dry weight was significantly negatively correlated with grain yield.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e3“significant negative correlations were found between tassel dry weight and grain yield”
Claim · model-written summary
Three-way hybrids with two DTP lines yielded more than those with one DTP line.
- Treatment
- Three-way hybrids involving two DTP linese4
- Outcome
- yieldede4
- Direction
- moree4
- Qualifier
- indicating the feasibility of gene pyramiding for drought tolerancee4
- Comparator
- those involving one onlye4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e4“Three-way hybrids involving two DTP lines yielded more than those involving one only, indicating the feasibility of gene pyramiding for drought tolerance”
Claim · model-written summary
Mean grain weight, not used before in a drought selection index, was strongly correlated with yield.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e5“Mean grain weight, previously not used within a drought selection index, was strongly correlated with yield in the present study”
Claim · model-written summary
The relationship between grain yield and secondary traits has been modified by continuous selection in the LPS and DTP populations.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e6“Overall, the results suggested that the relationship between grain yield and secondary traits has been modified due to continuous selection in the LPS and DTP populations”
Claim · model-written summary
Some long-established secondary traits have become less important, while others have become more relevant, under continuous selection.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e6“Overall, the results suggested that the relationship between grain yield and secondary traits has been modified due to continuous selection in the LPS and DTP populations”
e7“Some long-established secondary traits have become less important, while others have become more relevant”
Claim · model-written summary
Traits of source organs contribute only marginally to drought tolerance.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e1“The results indicate that the traits of source organs contribute marginally to drought tolerance”
Claim · model-written summary
Variation of leaf or root traits is less important than variation in tassel parameters for increasing drought tolerance.
- Organ / stage
- leaf or roote1
- Outcome
- variation of leaf or root traitse1
- Direction
- less importante1
- Comparator
- variation in tassel parameterse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e1“variation of leaf or root traits seems to be less important than variation in tassel parameters for increasing drought tolerance”
Claim · model-written summary
Selection for more ears, bigger grains and smaller tassels may increase grain yield under water-limited environments.
- Outcome
- selection for even greater number of ears, bigger grains and smaller tasselse1
- Setting
- water limited environmentse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e1“It is therefore suggested that selection for even greater number of ears, bigger grains and smaller tassels may help to increase grain yield under water limited environments in the near future”
Claim · model-written summary
Secondary-trait selection and water-stress management with recurrent selection increased drought tolerance in the CIMMYT maize DTP and LPS populations.
- Material
- Drought Tolerant Population (DTP)e1
- Treatment
- management of water stress and recurrent selectione1
- Outcome
- drought tolerancee1
- Direction
- increasee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“drought tolerance in maize”
e1“together with management of water stress and recurrent selection, have permitted a considerable increase in drought tolerance in the CIMMYT maize source germplasm populations Drought Tolerant Population (DTP) and La Posta Sequía (LPS)”
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