title: Combined linkage and association mapping identifies a major QTL (qRtsc8-1), conferring tar spot complex resistance in maize.
abstract: A major QTL ( qRtsc8 - 1 ) conditioning resistance to tar spot complex of maize and occurring at a frequency of 3.5 % across 890 maize inbred lines. Tar spot complex (TSC) is a highly destructive disease of maize found in some countries in America. Identification of TSC resistant germplasm and elucidating the genetic mechanism of resistance is crucial for the use of host resistance to manage this disease. We evaluated 890 elite maize inbred lines in multiple environments and used genome wide association analysis (GWAS) with genotypic data from Illumina MaizeSNP50 BeadChip containing 56 K SNPs to dissect the genetics of TSC resistance. GWAS results were validated through linkage analysis in three bi-parental populations derived from different resistant and susceptible parents. Through GWAS, three TSC resistance loci were identified on chromosome 2, 7 and 8 (-log10 (p) > 5.99). A major quantitative resistance locus (QTL) designated qRtsc8-1, was detected on maize chromosome bin 8.03. qRtsc8-1, was confirmed in three independent bi-parental populations and it accounted for 18-43 % of the observed phenotypic variation for TSC. A rare haplotype within the qRtsc8-1 region, occurring at a frequency of 3.5 % increased TSC resistance by 14 %. Candidate gene analysis revealed that a leucine-rich repeat receptor-like protein (LRR-RLKs) gene family maybe the candidate gene for qRtsc8-1. Identification and localization of a major locus conditioning TSC resistance provides the foundation for fine mapping qRtsc8-1 and developing functional markers for improving TSC resistance in maize breeding programs. To the best of our knowledge, this is the first report of a major QTL for TSC resistance.
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), ICRAF Campus, UN Avenue, Gigiri, PO Box 1041-00621, Nairobi, Kenya. g.mahuku@cgiar.org.|International Institute of Tropical Agriculture (IITA), P.O.Box, 34443, Dar es Salaam, Tanzania. g.mahuku@cgiar.org.
authors.forename: George
authors.identifier: http://orcid.org/0000-0001-8444-8651
authors.initials: G
authors.lastname: Mahuku
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600, Mexico, DF, Mexico.|College of Agronomy, Henan Agricultural University, Zhengzhou, 450002, China.
authors.forename: Jiafa
authors.initials: J
authors.lastname: Chen
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600, Mexico, DF, Mexico.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Shrestha
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Aereo 67-13, Cali, Colombia.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Narro
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Aereo 67-13, Cali, Colombia.
authors.forename: Karen Viviana Osorio
authors.initials: KV
authors.lastname: Guerrero
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Aereo 67-13, Cali, Colombia.
authors.forename: Alba Lucia
authors.initials: AL
authors.lastname: Arcos
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT) and Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
authors.forename: Yunbi
authors.initials: Y
authors.lastname: Xu
mesh_terms: D001203:Ascomycota; D002874:Chromosome Mapping; D060467:Disease Resistance / Q000235:genetics*; D056726:Genetic Association Studies; D008040:Genetic Linkage; D005838:Genotype; D006239:Haplotypes; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci; D003313:Zea mays / Q000235:genetics*