Genome-wide association mapping of flowering time and northern corn leaf blight (Setosphaeria turcica) resistance in a vast commercial maize germplasm set

Delphine Van Inghelandt,Jean-Pierre Martinant,Benjamin Stich,Albrecht E Melchinger

doi:10.1186/1471-2229-12-56

Abstract

BackgroundSetosphaeria turcica is a fungal pathogen that causes northern corn leaf blight (NCLB) which is a serious foliar disease in maize. In order to unravel the genetic architecture of the resistance against this disease, a vast association mapping panel comprising 1487 European maize inbred lines was used to (i) identify chromosomal regions affecting flowering time (FT) and northern corn leaf blight (NCLB) resistance, (ii) examine the epistatic interactions of the identified chromosomal regions with the genetic background on an individual molecular marker basis, and (iii) dissect the correlation between NCLB resistance and FT.ResultsThe single marker analyses performed for 8 244 single nucleotide polymorphism (SNP) markers revealed seven, four, and four SNP markers significantly (α=0.05, amplicon wise Bonferroni correction) associated with FT, NCLB, and NCLB resistance corrected for FT, respectively. These markers explained individually between 0.36 and 14.29% of the genetic variance of the corresponding trait.ConclusionsThe very well interpretable pattern of SNP associations observed for FT suggested that data from applied plant breeding programs can be used to dissect polygenic traits. This in turn indicates that the associations identified for NCLB resistance might be successfully used in marker-assisted selection programs. Furthermore, the associated genes are also of interest for further research concerning the mechanism of resistance to NCLB and plant diseases in general, because some of the associated genes have not been mentioned in this context so far.

Highlights

Setosphaeria turcica is a fungal pathogen that causes northern corn leaf blight (NCLB) which is a serious foliar disease in maize
The population background structure accounted for 21, 6, and 2% of the genetic variation in flowering time (FT), NCLB and NCLB resistance corrected for FT (NCLBFT ), respectively
Our observation explains why we found neither for the whole set of genotypes nor in the individual heterotic pools any overlap between single nucleotide polymorphism (SNP) associated with FT and NCLB (Table 2, 3, 4; Figure 3), and no evidence of a pleiotropic effect of FT on NCLB resistance at the SNP level which is in accordance with results of [16]

Summary

Introduction

Setosphaeria turcica is a fungal pathogen that causes northern corn leaf blight (NCLB) which is a serious foliar disease in maize. In order to unravel the genetic architecture of the resistance against this disease, a vast association mapping panel comprising 1487 European maize inbred lines was used to (i) identify chromosomal regions affecting flowering time (FT) and northern corn leaf blight (NCLB) resistance, (ii) examine the epistatic interactions of the identified chromosomal regions with the genetic background on an individual molecular marker basis, and (iii) dissect the correlation between NCLB resistance and FT. Setosphaeria turcica (anamorph Exserohilum turcicum, formerly known as Helminthosporium turcicum) is a fungal pathogen that causes northern corn leaf blight (NCLB) in maize. Plants have evolved qualitative and quantitative resistance to combat pathogens. All these aspects limit the practical value of the Ht genes and have hampered their use in maize breeding programs

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Conclusion