1. W. Wen, T. Guo, V.H. Chavez T., J. Yan, S. Taba CIMMYT
The strategy and potential utilization of temperate germplasm for tropical germplasm improvement—a case study of maize (Zea Mays L.)
W. Wen, T. Guo, V.H. Chavez T., J. Yan, S. Taba
CIMMYT

2. Heterotic groups A, B, C, D……X B C X D
Heterosis exploitation
Organization of germplasm in genetically divergent heterotic groups is beneficial for a systematic and optimum exploitation of heterosis (Melchinger 1999).
Well-developed heterotic patterns of mature breeding programs are artificial constructs created by breeders and enhanced by the process of breeding hybrids (Tracy and Chandler 2006)

3. CML: CIMMYT Maize Lines ,Tropical
GEM: US Germplasm Enhancement of Maize (GEM) lines, Temperate

4. The CMLs originated from 35 mostly broad-based populations and pools with mixed origins, which are carefully selected inbred lines with good general combining ability (GCA) and a significant number of value-adding traits such as drought tolerance, nitrogen (N) use efficiency, acid soil tolerance, resistance to disease and insect pests (
To date, the total number of CMLs held in trust in CIMMYT genebank is 530.

5. The Germplasm Enhancement of Maize project (GEM) is a cooperative effort of the United States Department of Agriculture’s Agricultural Research Service (USDA-ARS), land-grant universities, private industry, international, and non-governmental organizations.
The objective is widening the germplasm base of commercial hybrid corn in the United States through introduction and incorporation of novel and useful germplasm gathered from around the globe (

6. Features of CMLs
The lack of structure within CMMYT lines and lower genetic distance between current heterotic groups due to the mixed genetic constitution of CIMMYT germplasm used to extract the inbred lines.

7. Why use temperate germplasm?
Some favorable alleles may be unique to temperate germplasm, for instance, the allele of the gene encoding β-carotene hydroxylase (crtRB1), associated with β-carotene concentration and conversion in maize kernels, which was detected most recently (Yan et al. 2010)
Some GEM lines performed well in tropical and subtropical areas.
There should be favorably unique alleles or genomic regions in temperate germplasm that can be helpful in tropical maize improvement as well as utilization of tropical lines in temperate areas.

8. Traditional MAS
Including two steps: identifying QTL and then estimating their effects.
Weakness of QTL identification methods:
Biparental populations, not representative, do not have the same level of allelic diversity and phase as the breeding program as a whole
Costly
Additional effort is needed to validate the mapping results
Biased estimation

9. Genomic selection
Genomic selection which involves calculating breeding values for all markers and utilizes all markers in selection without testing them for their significance may dramatically change the role of phenotyping especially with the rapid development of high through-put genotyping platform (Jannink et al. 2010)
Heffner et al. 2009

10. Objectives
to detect the potential of utilizing temperate germplasm in tropical maize breeding
to construct a simple model using information of phenotypic values and molecular markers to predict single crosses (hybrid) performance
to compare the efficiency of hybrid performance prediction by using random markers and selective markers with association analysis

11. Material Summary Heterotic Pattern Number Description CML A 48
Dent kernel B 38
Flint kernel
A/B 8
Dent/Flint kernel
GEM SS 35
Stiff stalk
NSS 19
Non-stiff stalk
Total
148 F1
654
F1: CML (A) X GEM (SS), CML (B) X GEM (NSS)

12. CML
GEM F1

13. Phenotyping F1/TL F1/AF Inbreds/TL Inbreds/AF Trait Range Mean
DA (day)
76-103
92.11 ±4.66
60-82
71.44 ±4.04
80-103
92.01 ±4.13
71.31 ±3.71
DS (day)
76-106
93.09 ±4.82
61-82
71.01 ±3.74
80-106
92.98 ±4.30
61-80
70.92 ±3.46
PH (cm)
±21.48
±18.25
±17.30
±14.21
EH (cm)
50-170
112.1 ±18.68
±17.82
70-150
112.6 ±15.43
85-165
±14.36
EW (kg)
0.87 ±0.37
0.85 ±0.46
0.92 ±0.34
0.95 ±0.49
EWP (kg)
0.27 ±0.09
0.43 ±0.14
0.28 ±0.08
0.43 ±0.09

14. SNPs used for genotyping
Chromosome
No. of SNPs 1
217 2
132 3
140 4
134 5
154 6 98 7 77 8
115 9 96 10 83
Unknown 20
Total
1,266

15. The frequency of the same specific allele of each SNP in GEM lines, CMLs and all 148 lines.

16. Principal component analysis (PCA) of 148 maize inbred lines based on 1266 SNPs

17. Principal component analysis (PCA) of 654 maize F1 lines based on 872 SNPs

19. Prediction of hybrid performance
Training sample set: n=430
Testing sample set: n=215

20. Prediction of hybrid performance
Marker type A: marker selection referring to association results from inbreds, and starting from the marker with highest significance.
Marker type B: marker selection referring to association results from F1s, and starting from the marker with highest significance.
Marker type C: markers selected randomly from the genome-covering 1,266 SNPs

21. Implication and discussion
Utilizing temperate lines in tropical breeding program
In this study, unique alleles harbored within the temperate lines imply the utilization of temperate lines in tropical breeding program and the potential of mutual improvement
Clear heterotic patterns of the GEM lines can broaden the genetic divergence between heterotic groups within CMLs

22. The potential and strategy of genomic selection in maize breeding
The high prediction accuracy indicates the potential and efficiency of genomic selection based on our model, for predicting hybrid performance.
Replacing a larger number of genome-covering markers with a smaller number of trait-associated markers may be more effective because the latter produces less noise

23. PPB in Oaxaca Project
Trails of landrace collections, hybrids, CIMMYT gene pools
Seed production of hybrids and inter-varietal hybrids in Central Valley of Oaxaca
Seed processing and Declared seeds for distribution
Low cost seed bags: pesos for 20kg.
Good yield and plant performance of some gene pools: potential useful gene flow into the local maize production communities

24. PPB in Valle Central, Oaxaca

25. End.
Thank you very much.