Identification of Alleles Conferring Resistance to Gray Leaf Spot in Maize Derived from its Wild Progenitor Species Teosinte

Abstract

Gray leaf spot (GLS; causal agent Cercospora zeae‐maydis and Cercospora zeina) is an important maize (Zea mays L.) disease in the United States. Current control methods for GLS include using resistant cultivars, crop rotation, chemical applications, and conventional tillage to reduce inoculum levels. Teosinte (Z. mays subsp. parviglumis) is the wild progenitor of maize and easily forms hybrids with current maize inbreds. The aims of this study were to identify alleles from teosinte that, when introduced into temperate maize germplasm, conferred significant levels of GLS resistance. A population of 693 BC4S2 near isogenic lines (NILs), developed by crossing nine different teosinte accessions into the background of the maize inbred B73, were evaluated for GLS resistance in replicated field trials over 2 yr. Six markers significantly associated with GLS resistance were identified using 768 single nucleotide polymorphism (SNP) markers used to genotype this population. Twenty‐seven individual NILs that differed significantly from B73 for GLS resistance and that carried teosinte introgressions at the significantly associated SNPs at bins 2.04, 3.06, 4.07, 5.03, 8.06, and 9.03 were selected for follow‐up studies. F2:3 populations were developed by crossing each selected NIL to B73 followed by self‐pollinating the progeny twice. These F2:3 populations were evaluated for GLS resistance and genotyped at the loci of interest. In most cases, single‐marker analysis validated predicted allelic substitution effects from the original NIL populations.

Identification of Teosinte Alleles for Resistance to Southern Leaf Blight in Near Isogenic Maize Lines

“…Gevers and Lake (1994) identified a GLSresistance allele in a line derived from two teosintes (Z. mays subsp. Soybean leaf blight resistance may be a case in point since, in contrast to our GLS resistance study (Lennon et al, 2015), we have no evidence that the alleles identified in this study are superior to or distinct from resistance alleles that were previously identified in cultivated maize. Maize breeders and plant breeders in general are often reluctant to introduce sources of exotic germplasm into their programs since, as well as a few valuable alleles, many deleterious alleles may be introduced.…”

“…Of the six DTA-QTLs identified in this study, two of them, those on chromosome 8 and 10, were also found as DTA-QTL in our previous study which assessed the same populations for GLS resistance (Lennon et. al., 2015).…”

“…B73 is a known susceptible line while the two NC developed lines carry resistance to SLB. Lennon et al 2015. ) planted on 2 May 2011, 20 and 27 Apr.…”

“…Imputed scores for non-informative (i.e., monomorphic) or missing markers in specific populations were based on the flanking marker genotypes as previously described (Buckler et al, 2009). The model was optimized and support intervals were found using the same method as described in Lennon et al (2015). The NAM genetic map was used for the QTL analysis (McMullen et al, 2009).…”

QTL mapping for resistance of maize to grey leaf spot

“…() constructed an F 2 population with Y32 × Ye478 and detected QTLs on chromosomes 2, 3, 4, 5, and 8 that were related to GLS resistance and explained 2.9%‐19.9% of the phenotypic variation. Lennon, Krakowsky, Goodman, Flint‐Garcia, and Balint‐Kurti () obtained RILs by hybridizing teosinte with B73 for resistance QTL mapping and found that resistance genes were located in bins 2.04, 3.06, 4.07, 5.03, 8.06, and 9.03. Mammadov et al.…”