Genome-wide association mapping reveals novel sources of resistance to northern corn leaf blight in maize.
BACKGROUND
Northern corn leaf blight (NCLB) caused by Exserohilum turcicum is a destructive disease in maize. Using host resistance to minimize the detrimental effects of NCLB on maize productivity is the most cost-effective and appealing disease management strategy. However, this requires the identification and use of stable resistance genes that are effective across different environments.


RESULTS
We evaluated a diverse maize population comprised of 999 inbred lines across different environments for resistance to NCLB. To identify genomic regions associated with NCLB resistance in maize, a genome-wide association analysis was conducted using 56,110 single-nucleotide polymorphism markers. Single-marker and haplotype-based associations, as well as Anderson-Darling tests, identified alleles significantly associated with NCLB resistance. The single-marker and haplotype-based association mappings identified twelve and ten loci (genes), respectively, that were significantly associated with resistance to NCLB. Additionally, by dividing the population into three subgroups and performing Anderson-Darling tests, eighty one genes were detected, and twelve of them were related to plant defense. Identical defense genes were identified using the three analyses.


CONCLUSIONS
An association panel including 999 diverse lines was evaluated for resistance to NCLB in multiple environments, and a large number of resistant lines were identified and can be used as reliable resistance resource in maize breeding program. Genome-wide association study reveals that NCLB resistance is a complex trait which is under the control of many minor genes with relatively low effects. Pyramiding these genes in the same background is likely to result in stable resistance to NCLB.
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China. dingjunqiang1203@163.com.
Junqiang
J
Ding
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China. farhan_198@yahoo.com.
Farhan
F
Ali
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China. gengshencgs@126.com.
Gengshen
G
Chen
Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, 100081, China. lihuihui@caas.cn.
Huihui
H
Li
Global Maize Program, International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600, Mexico, DF, Mexico. g.mahuku@cgiar.org.
George
G
Mahuku
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China. ningyangmaizego@gmail.com.
Ning
N
Yang
Global Maize Program, International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600, Mexico, DF, Mexico. l.narro@cgiar.org.
Luis
L
Narro
Global Maize Program, International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600, Mexico, DF, Mexico. c.magorokosho@cgiar.org.
Cosmos
C
Magorokosho
Global Maize Program, International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600, Mexico, DF, Mexico. d.makumbi@cgiar.org.
Dan
D
Makumbi
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China. yjianbing@mail.hzau.edu.cn.
Jianbing
J
Yan
D000704:Analysis of Variance; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D060467:Disease Resistance / Q000235:genetics*; D017343:Genes, Plant; D056726:Genetic Association Studies; D056426:Genetic Loci; D055106:Genome-Wide Association Study; D006239:Haplotypes / Q000235:genetics; D040582:Inheritance Patterns / Q000235:genetics; D058977:Molecular Sequence Annotation; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics / Q000382:microbiology*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D003313:Zea mays / Q000235:genetics* / Q000382:microbiology*