Maize Introgression Library Provides Evidence for the Involvement ofliguleless1in Resistance to Northern Leaf Blight

Abstract

Plant disease resistance is largely governed by complex genetic architecture. In maize, few disease resistance loci have been characterized. Near-isogenic lines are a powerful genetic tool to dissect quantitative trait loci. We analyzed an introgression library of maize (Zea mays) near-isogenic lines, termed a nested near-isogenic line library for resistance to northern leaf blight caused by the fungal pathogen Setosphaeria turcica. The population was comprised of 412 BC5F4 near-isogenic lines that originated from 18 diverse donor parents and a common recurrent parent, B73. Single nucleotide polymorphisms identified through genotyping by sequencing were used to define introgressions and for association analysis. Near isogenic lines that conferred resistance and susceptibility to northern leaf blight were comprised of introgressions that overlapped known northern leaf blight quantitative trait loci. Genome-wide association analysis and stepwise regression further resolved five quantitative trait loci regions, and implicated several candidate genes, including Liguleless1, a key determinant of leaf architecture in cereals. Two independently-derived mutant alleles of liguleless1 inoculated with S. turcica showed enhanced susceptibility to northern leaf blight. In the maize nested association mapping population, leaf angle was positively correlated with resistance to northern leaf blight in five recombinant inbred line populations, and negatively correlated with northern leaf blight in four recombinant inbred line populations. This study demonstrates the power of an introgression library combined with high density marker coverage to resolve quantitative trait loci. Furthermore, the role of liguleless1 in leaf architecture and in resistance to northern leaf blight has important applications in crop improvement.

Global warming and increasing maize cultivation demand comprehensive efforts in disease and insect resistance breeding in north‐western Europe

“…However, many more genes behind the QTLs must be characterized (Martins et al, 2019) and additional breeding schemes must be developed and/or existing ones adapted (Wisser et al, 2006) in order to find a suitable way through the “jungle” of uncharacterized QTLs. One strategy is the development of an introgression library combined with high density marker coverage to resolve QTLs (Kolkman et al, 2020).…”

“…One strategy is the development of an introgression library combined with high density marker coverage to resolve QTLs (Kolkman et al, 2020).…”

Genotypic and phenotypic characterization of a large, diverse population of maize near‐isogenic lines

“…Near‐isogenic lines (NILs) have been used extensively to characterize, validate and dissect QTL in maize (Szalma et al , 2007; Pea et al , 2009; Chung et al , 2010; Eichten et al , 2011; Mideros et al , 2014; Peiffer et al , 2014; Benson et al , 2015; Lennon et al , 2016, 2017; Xiao et al , 2016; Kolkman et al , 2019; Martins et al , 2019). However, the development of NILs is time‐consuming and costly, as it requires several generations of backcrossing, selfing and genotyping.…”

“…Via the International Maize and Wheat Improvement Center (CIMMYT), Syngenta AG (Basel, Switzerland) has made public a large panel of maize NILs derived from crosses between 25 diverse inbred lines and B73, henceforth referred to as the Syngenta panel (Gandhi et al , 2008). Kolkman et al (2019) recently used a subset of 412 ‘nested’ NILs (nNILs) from the Syngenta panel, which were chosen for having introgressions surrounding disease resistance QTL, for GWA and candidate gene identification of resistance to northern leaf blight (NLB).…”

Genome-wide association studies in tropical maize germplasm reveal novel and known genomic regions for resistance to Northern corn leaf blight

“…A major QTL was identified for AUDPC on chromosome 8 between the bins 8.05–8.06 in F 2:3 populations studied for NCLB resistance 53 . Recently, a study conducted on a nested near isogenic line library for resistance to NCLB, also identified NILs with introgressions across centromeric region of chromosome 8 (bin 8.05), which overlaps two major genes ht2 and htn 54 . The fact that one of our mapping panels also identified a strongly associated set of closely located SNPs in this important chromosomal bin, indicated possible presence of a quantitatively expressed major gene or dQTL in this region present in the genetic background of the maize lines of this particular panel.…”