Qtl associated with maize kernel traits among illinois high oil b73 backcross derived lines
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QTL Associated with Maize Kernel Traits among Illinois High Oil × B73 Backcross-Derived Lines. By J.J. Wassom, J.C. Wong, and T.R. Rocheford University of Illinois, Department of Crop Sciences. Illinois High Oil Maize. Recurrent selection for oil in Illinois High Oil (IHO) since 1896.

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Qtl associated with maize kernel traits among illinois high oil b73 backcross derived lines l.jpg

QTL Associated with Maize Kernel Traits among Illinois High Oil × B73 Backcross-Derived Lines

By

J.J. Wassom, J.C. Wong, and

T.R. Rocheford

University of Illinois,

Department of Crop Sciences


Illinois high oil maize l.jpg
Illinois High Oil Maize Oil

  • Recurrent selection for oil in Illinois High Oil (IHO) since 1896.

    • 4.7% of kernel weight at start.

    • 19.3% of kernel weight at cycle 90.


Slide3 l.jpg

IHO Oil


Practical advantages of grain from high oil maize l.jpg
Practical Advantages of Grain from High-oil Maize Oil

  • Livestock feeding value is improved.

    • More calories.

    • Improved amino acid balance.

  • Improved oil quality.

    • Oleic acid tends to increase with higher oil.

      • a mono-unsaturated fatty acid.

  • Oil: one factor in overall improvement.


Selection for oil l.jpg
Selection for Oil Oil

  • Ample genetic variation for oil.

  • High-oil maize typically has:

    • Small kernels.

    • Large embryo and small endosperm.

    • Reduced starch and increased protein.

  • Heritable, but high-oil hybrids yield less.

    • About 8% less for the current market leader.


Kernel oil protein and starch interact l.jpg
Kernel oil, protein, and starch interact Oil

  • Most stored lipids of the maize kernel accumulate in the scutellum of the embryo.

  • High oil maize typically has:

    • Large embryo and small endosperm.

    • Small kernels.

    • Reduced starch and increased protein.



Previous kernel qtl studies l.jpg
Previous Kernel QTL Studies Oil

  • IHO × ILO markers for oil, protein, and starch (Berke and Rocheford, 1995).

  • But this population is not representative of modern hybrids.


Objectives in this study l.jpg
Objectives in This Study Oil

  • In a population more relevant to practical hybrids:

    • Analyze variation for kernel traits.

    • Develop a molecular map.

    • Identify QTL for kernel oil, protein, starch, and related traits and determine their effects in genetic models.

    • Identify QTL with potential in MAS.


Materials and methods l.jpg
Materials and Methods Oil

  • 150 backcross1-derived S1 lines (BC1S1).

  • High oil donor: IHO cycle 90.

    • One plant.

  • Recurrent parent: B73.

    • Historically important BSS inbred line.

  • Testcrosses (TC) with Mo17.

    • Historically important Lancaster inbred line.


Materials and methods11 l.jpg
Materials and Methods Oil

  • Field trials at Urbana, IL.

  • BC1S1 : 1993, 1994, 1996, 2000, and 2001.

  • TC:1995 and 1996.

  • Kernel oil, starch, and protein each year.

  • Fatty acids in BC1S1 in 1993 and 1994.


Materials and methods12 l.jpg
Materials and Methods Oil

  • Linkage map:

    • 110 markers, 38 RFLP and 72 SSR.

    • Total length = 1486 cM.

    • Average distance between markers = 14.9 cM.

  • Composite interval mapping.

    • LOD 2.5 for detection.

    • Models developed with genome-wide  = 0.05.

    • Additive and additive × additive effects.


Materials and methods13 l.jpg
Materials and Methods Oil

  • Heritability: h2 = 2g/ (2 /re + 2ge/e +2g).

    • (Hallauer and Miranda, 1981)

  • Adjusted R2: R2adj = R2 – [z/(n-z-1)](1-R2).

    • R2 = coefficient of determination

    • z = number of QTL and interaction terms

    • n = number of individuals

  • Q2 = R2adj/h2

    • (Utz et al., 2000)


  • Kernel traits among bc 1 s 1 families l.jpg
    Kernel traits among BC Oil 1:S1families






    Summary of models in bc 1 s 1 s l.jpg
    Summary of Models Oil inBC1S1s




    Slide22 l.jpg

    Detected in BC1:S1 Oil

    Detected in TC

    B73 favors oil

    IHO90 favors oil

    QTL for kernel oil detected at LOD 2.5.


    Slide23 l.jpg

    Chromosome 6 with oil, oleic acid, protein, and starch QTL in BC1S1 highlighted.

    QTL LOD Trait Favorable Allele

    20 2.71 Oleic IHO90

    50 16.62 Oleic IHO90

    50 4.17 Starch B73

    64 17.19 Oil IHO90

    72 5.37 Protein IHO90

    92 3.77 Protein IHO90

    Oil

    Oleic acid

    B73

    Protein

    Starch

    IHO90


    Intervals affecting multiple traits l.jpg
    Intervals affecting multiple traits in BC

    • Many QTL are clustered within intervals (22 cM) affecting multiple traits.

    • Direction of the QTL effects on different traits often follow expectations based on trait correlations.


    Slide25 l.jpg

    O in BC

    S

    P

    P

    S

    S

    P

    P

    S

    O

    S

    P

    O

    S

    S

    P

    O

    Y

    S

    P

    O

    O

    P

    P

    S

    S

    P

    Y

    S

    P

    S

    Y

    O

    S

    Intervals associated with common effects on oil, protein, starch, and grain yield are highlighted.Letters at the left indicate the associated trait.


    Slide26 l.jpg

    Chromosome 6: All QTL with LOD > 2.5. Common QTL intervals are shown as rectangles. QTL outside common intervals are shown as triangles.

    Interval LOD Generation Trait Favorable Allele

    8 to 20 3.38 TC Starch B73

    8 to 20 3.51 TC Protein IHO90

    8 to 20 2.79 BC1S1 Oleic IHO90

    50 to 72 16.62 BC1S1 Oleic IHO90

    50 to 72 4.17 BC1S1 Starch B73

    50 to 72 17.19 BC1S1 Oil IHO90

    50 to 72 5.37 BC1S1 Protein IHO90

    74 5.45 TC Oil IHO90

    92 3.77 BC1S1 Protein IHO90


    Summary l.jpg
    Summary are shown as rectangles. QTL outside common intervals are shown as triangles.

    • QTL were detected for all traits.

    • Models in BC1S1s explained:

      • 47% of the phenotypic and 54% of the genotypic variation for oil.

      • 51% of the phenotypic and 60% of the genotypic variation for oleic acid.


    Summary28 l.jpg
    Summary are shown as rectangles. QTL outside common intervals are shown as triangles.

    • One QTL on chromosome 6L in BC1S1 explained:

      • 37% of the phenotypic variation for oil.

    • A nearby QTL on 6L explained:

      • 24% of the phenotypic variation for oleic acid.

    • Markers flanking these QTL show promise for MAS of high-oil, high-oleic lines.

    • Many QTL for different kernel traits are clustered within common chromosome regions.


    Marker assisted selection l.jpg
    Marker Assisted Selection are shown as rectangles. QTL outside common intervals are shown as triangles.

    • Separate oil from yield.

    • Molecular markers identify high oil genomic regions.

    • Directly select for markers.

      • Modify recurrent parent for oil-related genes only.


    Slide30 l.jpg

    Introgression of minimal chromosomal segments, especially on chromosome 6L, from a high-oil donor into conventional breeding lines may enhance the development of agronomically desirable and productive high-oil breeding lines and hybrids.


    Acknowledgements l.jpg
    Acknowledgements chromosome 6L, from a high-oil donor into conventional breeding lines may enhance the development of agronomically desirable and productive high-oil breeding lines and hybrids.

    • Funded by a grant from the Illinois-Missouri Biotechnology Alliance with matching support from Monsanto Company.

    • Lab members, past and present.

      • Jeremy Johnson

      • Joe King

      • Venu Mikkillineni

      • Chandra Paul

    • Fatty acid measurement.

      • Jan Hazebroek and associates at Pioneer Hi-Bred International


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