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Open AccessArticle

Identification and Validation of Candidate Genes Conferring Resistance to Downy Mildew in Maize (Zea mays L.)

1
Department of Life Science, Dongguk University-Seoul, Seoul 04620, Korea
2
Department of Plant Resources, College of Industrial Science, Kongju National University, Yesan 32439, Korea
*
Author to whom correspondence should be addressed.
Genes 2020, 11(2), 191; https://doi.org/10.3390/genes11020191
Received: 2 January 2020 / Revised: 5 February 2020 / Accepted: 5 February 2020 / Published: 11 February 2020
(This article belongs to the Special Issue Genetics and Epigenetics of Biotic Stress Response in Plants)
Downy mildew (DM) is a major disease of maize that causes significant yield loss in subtropical and tropical regions around the world. A variety of DM strains have been reported, and the resistance to them is polygenically controlled. In this study, we analyzed the quantitative trait loci (QTLs) involved in resistance to Peronosclerospora sorghi (sorghum DM), P. maydis (Java DM), and Sclerophthora macrospora (crazy top DM) using a recombinant inbred line (RIL) from a cross between B73 (susceptible) and Ki11 (resistant), and the candidate genes for P. sorghi, P. maydis, and S. macrospora resistance were discovered. The linkage map was constructed with 234 simple sequence repeat (SSR) and restriction fragment length polymorphism (RFLP) markers, which was identified seven QTLs (chromosomes 2, 3, 6, and 9) for three DM strains. The major QTL, located on chromosome 2, consists of 12.95% of phenotypic variation explained (PVE) and a logarithm of odds (LOD) score of 14.12. Sixty-two candidate genes for P. sorghi, P. maydis, and S. macrospora resistance were obtained between the flanked markers in the QTL regions. The relative expression level of candidate genes was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) using resistant (CML228, Ki3, and Ki11) and susceptible (B73 and CML270) genotypes. For the 62 candidate genes, 15 genes were upregulated in resistant genotypes. Among these, three (GRMZM2G028643, GRMZM2G128315, and GRMZM2G330907) and AC210003.2_FG004 were annotated as leucine-rich repeat (LRR) and peroxidase (POX) genes, respectively. These candidate genes in the QTL regions provide valuable information for further studies related to P. sorghi, P. maydis, and S. macrospora resistance.
Keywords: maize; downy mildew; QTL; qRT-PCR; RILs maize; downy mildew; QTL; qRT-PCR; RILs
MDPI and ACS Style

Kim, H.C.; Kim, K.-H.; Song, K.; Kim, J.Y.; Lee, B.-M. Identification and Validation of Candidate Genes Conferring Resistance to Downy Mildew in Maize (Zea mays L.). Genes 2020, 11, 191.

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