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Published on: September 2, 2019
QTL mapping with near-isogenic lines in maize
S J Szalma1, B M Hostert, J R Ledeaux
1USDA-ARS Plant Science Research Unit and Department of Crop Science, North Carolina State University, Raleigh, NC 27695, USA.
Summary
Maize near-isogenic lines (NILs) were developed using marker-assisted selection to map quantitative trait loci (QTLs) for flowering time. These NILs significantly reduced background introgression, providing a valuable resource for maize genetics research.
Area of Science:
- Plant Genetics
- Maize Breeding
- Quantitative Genetics
Background:
- Developing near-isogenic lines (NILs) is crucial for dissecting complex genetic traits in crops.
- Marker-assisted selection (MAS) enhances the efficiency of NIL development by precisely tracking introgressed genomic regions.
Purpose of the Study:
- To create a set of maize NILs with targeted introgressions from donor line Tx303 into the B73 background.
- To utilize these NILs for mapping quantitative trait loci (QTLs) associated with flowering time in both inbred and hybrid maize.
- To assess the efficiency of MAS in minimizing background introgression during NIL development.
Main Methods:
- Generated 89 maize NILs through three generations of backcrossing with MAS.
- Utilized restriction fragment length polymorphism (RFLP) and simple sequence repeat (SSR) markers to genotype NILs and estimate introgression sizes.
- Conducted field evaluations of NILs and their testcross hybrids over two years to map QTLs for flowering time traits (days to anthesis, days to silking, anthesis-silk interval).
Main Results:
- Tx303 introgressions averaged 60 cM, with 89% of the donor genome represented across NILs.
- Achieved significantly lower background introgression (average 2.5%) compared to conventional methods (expected 9.4%).
- Identified QTLs for flowering time in both inbred NILs and their hybrids, with distinct QTLs detected across different environments (including drought stress) and genetic backgrounds.
Conclusions:
- The developed maize NILs are a valuable resource for genetic mapping and dissecting the genetic architecture of flowering time.
- MAS is highly effective in producing high-quality NILs with minimal background introgression.
- Flowering time in maize is genetically complex, influenced by environment and genetic background, necessitating diverse mapping populations for comprehensive analysis.
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02:27Trihybrid Crosses
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Some of Mendel’s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A trihybrid cross is a combination of three individual monohybrid crosses. For example, plant height (tall vs. short), seed shape (round vs. wrinkled), and seed color (yellow vs. green).
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Some of Mendel’s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A trihybrid cross is a combination of three individual monohybrid crosses. For example, plant height (tall vs. short), seed shape (round vs. wrinkled), and seed color (yellow vs. green).
The F1 generation plants of a trihybrid cross are heterozygous for all three traits and produce eight gametes. Upon self-fertilization, these gametes have an equal chance to...