Genome-wide association mapping of spot blotch resistance in wheat association mapping initiative (WAMI) panel of spring wheat (Triticum aestivum L.).

Ram Narayan Ahirwar,Ramesh Chand,Arun Kumar Joshi,Dwijesh Chandra Mishra,Sundeep Kumar,Vinod Kumar Mishra,Neeraj Budhlakoti,Shweta Singh

doi:10.1371/journal.pone.0208196

Abstract

Spot blotch (SB) caused by Bipolaris sorokiniana, is one of the most important diseases of wheat in the eastern part of south Asia causing considerable yield loss to the wheat crop. There is an urgent need to identify genetic loci closely associated with resistance to this pathogen for developing resistant cultivars. Hence, genomic regions responsible for SB resistance were searched using a wheat association mapping initiative (WAMI) panel involving 287 spring wheat genotypes of different origin. Genome-wide association mapping (GWAM) was performed using single nucleotide polymorphism (SNP) markers from a custom 90 K wheat SNP array. A mixed linear model (MLM) was used for assessing the association of SNP markers with spot blotch resistance in three consecutive years. Three traits were measured: incubation period, lesion number and area under the disease progress curve (AUDPC). Significant SNP markers were found linked to five, six and four quantitative trait loci (QTLs) for incubation period, lesion number and AUDPC respectively. They were detected on 11 different chromosomes: 1A, 1B, 1D, 4A, 5A, 5B, 6A, 6B, 6D, 7A, 7B with marker R2 range of 0.083 to 0.11. The greatest number of significant SNP-markers was found for lesion number and AUDPC on chromosome 6B and 5B, respectively, representing a better coverage of B-genome by SNPs. On the other hand, the most significant and largest SNP markers for incubation period were detected on 6A and 4A chromosomes indicating that this trait is associated with the A-genome of wheat. Although, QTLs for spot blotch resistance have been reported in wheat on these same chromosomes, the association of incubation period and lesion number with SB resistance has not been reported in previous studies. The panel exhibits considerable variation for SB resistance and also provides a good scope of marker-assisted selection using the identified SNP markers linked to resistant QTLs.

Highlights

Wheat (Triticum aestivum L.), one of the most widely adapted cereal crops [1], provides around one-fifth of the total calories to the human population
We detected Marker–trait associations (MTAs) that closely corresponded to fourteen loci on four chromosomes that were previously identified and single nucleotide polymorphism (SNP) markers and GWAS have been useful for QTL discovery in spring wheat
Considerable phenotypic and molecular variation was observed in the wheat association mapping initiative (WAMI) panel used suggesting the diverse genetic background of the germplasm

Summary

Introduction

Wheat (Triticum aestivum L.), one of the most widely adapted cereal crops [1], provides around one-fifth of the total calories to the human population It provides 20% of the protein to more than 4.5 billion people in 94 developing countries [2]. In south Asia, wheat is cultivated in over 40 million hectare area, out of which around 25% falls under Eastern Gangetic Plains (EGP) which contributes only 16% to the total wheat production. The EGP of south Asia is characterized as the mega environment 5A due to prevalence of high temperature and humidity during the wheat growing season [5, 6].In this region, wheat production is significantly impacted due to spot blotch disease [6, 7, 8] which may cause yield loss up to 30% [9]. The causal organism of spot blotch (SB) is Bipolaris sorokiniana, which is an anamorph (teleomorph Cochliobolus sativus)

Methods

Results

Discussion

Conclusion