Identification and Fine Mapping of rhm1 Locus for Resistance to Southern Corn Leaf Blight in Maize^F

Abstract

rhm1 is a major recessive disease resistance locus for Southern corn leaf blight (SCLB). To further narrow down its genetic position, F(2) population and BC(1) F(1) population derived from the cross between resistant (H95(rhm) ) and susceptible parents (H95) of maize (Zea mays) were constructed. Using newly developed markers, rhm1 was initially delimited within an interval of 2.5 Mb, and then finally mapped to a 8.56 kb interval between InDel marker IDP961-503 and simple sequence repeat (SSR) marker A194149-1. Three polymorphic markers IDP961-504, IDP B2-3 and A194149-2 were shown to be co-segregated with the rhm1 locus. Sequence analysis of the 8.56 kb DNA fragment revealed that it contained only one putative gene with a predicted amino acid sequence identical to lysine histidine transporter 1 (LHT1). Comparative sequence analysis indicated that the LHT1 in H95(rhm) harbors a 354 bp insertion in its third exon as compared with that of susceptible alleles in B73, H95 and Mo17. The 354 bp insertion resulted in a truncation of the predicted protein of candidate resistance allele (LHT1-H95(rhm) ). Our results strongly suggest LHT1 as the candidate gene for rhm1 against SCLB. The tightly linked molecular markers developed in this study can be directly used for molecular breeding of resistance to Southern corn leaf blight in maize.

Limits on the reproducibility of marker associations with southern leaf blight resistance in the maize nested association mapping population

“…The nearest annotated gene to the associated SNP is ~60 kb downstream and encodes an RNA recognition motif (RRM)-containing protein (GRMZM2G132936). Another strong variant association (RMIP = 0.40) was in the LHT1 gene (GRMZM2G127342) on chromosome 6; this gene was previously suggested to be the causal factor for the classically defined rhm1 locus based on QTL fine-mapping [ 46 ]. One of the most significant SNPs (RMIP = 0.8) is 332 bp downstream of GRMZM2G099363 encoding a caffeoyl-CoA O-methytransferase (CCoAOMT), within a QTL region on chromosome 9 identified in other populations [ 27 , 42 ].…”

Quantitative Disease Resistance: Dissection and Adoption in Maize

“…In China, northern leaf blight (NLB, caused by the fungus Setosphaeria turcica) and head smut (caused by Sphacelotheca reiliana) are two major diseases in northeast corn regions (Bai et al, 1994;Jiang et al, 2012); stalk rots (mainly caused by Pythium inflatum Matthews and Fusarium graminearum), MRDD, southern leaf blight (SLB, caused by the fungus Cochliobolus heterostrophus), and southern rust (caused by the fungus Puccinia polysora) are major concerns in Yellow-Huai-Hai River plain corn regions (Lu et al, 1995;Zhao et al, 2012bZhao et al, , 2013Tao et al, 2013b;Wang et al, 2014); banded leaf and sheath blight (BLSB, caused by Rhizoctonia solani), gray leaf spot (GLS, caused by the fungi Cercospora zeae-maydis and Cercospora zeina), and ear rot (mainly caused by Fusarium verticillioides and Fusarium graminearum) are the most important diseases in southwest corn regions (Chen et al, 2013;Liu and Xu, 2013;Duan et al, 2016); head smut, common smut (caused by Ustilago maydis), and common rust (caused by Puccinia sorghi) are major prevalent diseases in the northwest corn belt (Wang et al, 2006(Wang et al, , 2014. In the United States in 2015, the prominent corn diseases in the northern states included NLB, anthracnose stalk rot (caused by Colletotrichum graminicola), GLS, Goss's wilt, southern rust, Fusarium (F. verticillioides) and Gibberella (F. graminearum) stalk rot; and in the southern states, Fusarium stalk rot, nematodes, GLS, southern rust, seedling blights, root rot, and NLB (Mueller et al, 2016).…”

60 Years of Development of the Journal of Integrative Plant Biology

“…2012; Zhang et al. 2012; Zhao et al. 2012), and “molecular cloning” (Wang and Xue 2005; Chang et al.…”