Identification and characterisation of eyespot resistance in wheat (PhD)

Abstract

Eyespot is an economically important disease of the stem base of wheat caused by two species of fungi,Oculimacula yallundae and Oculimacula acuformis. The aim of this work was to develop genetic tools for plant breeders so that resistances against these pathogen species can be introduced into wheat varieties to provide reliable control of the disease.

This study provided further understanding of the genetic location, function and efficacy of resistances in the variety Cappelle Desprez. The genetic location of Pch2 resistance from this variety was confirmed on the distal portion of chromosome 7AL and, using information from a previous gene expression study, two candidate genes for involvement in the Pch2 resistance response were identified. However, this study also revealed that Pch2 confers a significantly lower resistance against penetration by O. yallundae than against O. acuformis. As both pathogen species are present in the UK, this suggests that Pch2 should not be used as a ‘stand-alone’ resistance in wheat varieties.

In addition, an adult plant resistance on chromosome 5A of Cappelle Desprez was shown to also be effective in seedlings and was shown to provide protection against both O. yallundae and O. acuformis, suggesting that it could provide reliable protection against the disease in the field. This resistance was mapped on chromosome 5AL in both field trials and seedling bioassays, and the molecular marker Xgwm639 was identified to be closely associated with the resistance to aid selection by plant breeders.

Finally, this study fine-mapped the potent resistance gene Pch1, previously introduced into wheat from the relative Aegilops ventricosa. Conserved Orthologous Sequence (COS) markers were targeted to the Pch1region of chromosome 7DV. These were used to identify recombinants in the Ae. ventricosa segment and to fine map Pch1 using Brachypodium and rice as reference sequences. Molecular markers were identified for the efficient selection of the resistance and, furthermore, candidate gene regions in Brachypodium and rice were identified to enable map-based cloning of the resistance gene.