Identification of quantitative trait loci for sorghum leaf blight resistance

Abstract

Sorghum leaf blight and northern corn leaf blight, both caused by Exserohilum turcicum {(Pass.) K. J. Leonard and Suggs [syn. Setosphaeria turcica (Luttr.) K. J. Leonard and Suggs.]}, are major diseases of sorghum [Sorghum bicolor (L.) Moench] and maize (Zea mays L.), respectively. Examining the genetic architecture of resistance in sorghum will lead to a better understanding of the relationship between resistance in sorghum and maize, which can ultimately enhance management options in both crops. In 2018 and 2019, we evaluated two sorghum recombinant inbred line (RIL) populations for resistance to E. turcicum. The BTx623 × IS3620C and BTx623 × SC155 populations consisted of 235 and 81 RILs, respectively. Resistance in both populations was moderately to highly heritable. We identified a total of six quantitative trait loci (QTL) across the two populations. Three QTL with smallto moderate-effect sizes were identified in the BTx623 × IS3620C population. Three QTL, including a large-effect QTL on chromosome three that explained 24% of the variation, were identified in the BTx623 × SC155 population. We compared the identified QTL with the position of northern corn leaf blight candidate genes and found eight candidate resistance gene orthologs that colocalize with the sorghum leaf blight QTL. There were also several nucleotide-binding leucine-rich repeat encoding genes within the candidate intervals. Understanding host resistance in multiple species furthers our understanding of the Exserohilum turcicum patho-system.

A Genome-Wide Association Study of Nigerien and Senegalese Sorghum Germplasm of Exserohilum turcicum, the Causal Agent of Leaf Blight

“…In a maize GWAS study, multiple genes associated with SANT, WRKY, inositol-pentakis-phosphate 2-kinase, potassium uptake protein TrkA, and 4 phosphopante theinyl transferase were listed as top candidates against E. turcicum [24]. Lipps et al [25] used two sorghum recombinant-inbred-line (RIL) populations for resistance to E. turcicum and identified a total of six quantitative trait loci (QTLs) across the two populations. In this study, we examined E. turcicum resistance to over one hundred accessions originally collected from Niger and Senegal and evaluated in three locations in Senegal.…”

“…Likewise, many genes linked to our top candidate genes through network nodes are also associated with plant stress and defense responses, indicating the importance of the identified genes in this study. Overall, limited GWAS work has been conducted on sorghum leaf blight, compared to Northern corn leaf blight (NCLB) in Maize [24,25,37,38]. A GWAS on NCLB caused by Setosphaeria turcica (perfect stage of E. turcicum) identified 22 SNPs significantly associated with NCLB in three tropical maize germplasm mapping panels [38].…”

“…Using a GWAS on NCLB in maize, 81 genes were revealed, and 12 of these genes were shown to play a role in plant defense [24]. Recently, Lipps et al [25] detected six QTLs across two sorghum recombinant inbred line populations when evaluated for resistance against the leaf blight pathogen. All these GWAS on sorghum and maize against E. turcicum will continue to enhance our knowledge of the resistance mechanisms in these two economically important crops, thereby increasing our food security globally.…”