LAUSR

Hessian fly (Mayetiola destructor (Say)) is a major pest in wheat producing areas of United States, Canada, Europe, and North Africa but has not been found in Australia. Host plant resistance is thought to involve a similar strategy used against plant pathogen, and in this study, we sought to investigate whether disease-resistance gene markers can also be useful in selecting against Hessian fly attack. The genome-wide association study involved 251 wheat genotypes of diverse origin and 72 SNPs, selected on the basis of significant similarity of their associated contig sequences to putative disease resistance genes. A novel statistical approach for genome-wide scan was applied, which utilised genotype data scored as Null alleles in the mixed model, instead of deleting or treating them as missing alleles. The analyses identified four markers with significant associations at the 5% level, after applying the false discovery rate. These were located on chromosomes 4A, 4B, 5A and 7D, with the 5A locus mapping to the cluster of major genes that confer resistance to multiple Hessian fly biotypes. Amongst the diverse wheat accessions analysed, most of the susceptible phenotypes carried the A–G–C–C haplotype at the BS00064369, BS00007416, BS00077047 and HfrDrd_nt_143 loci, respectively. When heterozygotes were excluded, all the Australian wheat accessions carried this allelic combination. The combination of alleles conferring resistance depended on the origin of the wheat accessions, with ICARDA accessions carrying a preponderance of the C–C–CG–T. Of the 11 USA accessions used for this study, only Lola carried a favourable combination of alleles for resistance at these loci.