The integrated domain nucleotide-binding leucine-rich repeat (NLR-ID) gene, TaAdnr1, underlies Russian wheat aphid and stripe rust.

Mkhize, N. S.*1, Boshoff, W.2, Visser, B.2, Venter, E.1

1 Department of Botany and Plant Biotechnology, University of Johannesburg, Auckland Park, 2006
2 Department of Plant Science, University of the Free State, Bloemfontein, 9301

Plant defence against pests and pathogens depends on intracellular immune receptors. However, the mechanism of how wheat recognise and respond to pathogens and pests through these receptors lacks a comprehensive understanding. Global wheat production in several major production regions is challenged by rust and aphid infestations leading to major economic and agricultural losses. Thus, the emergence of resistance breaking rust races and aphid biotypes increases the threat to food security. Recognition of pest and pathogen effectors in plants often depends on the presence of nucleotide-binding leucine-rich repeat (NLR) immune receptor proteins. The wheat NLR-ID gene TaAdnr1, containing atypical integrated WRKY and Ankyrin repeat domains, contributes to Dn1 and Dn7-mediated resistance response in the hexaploid wheat Triticum aestivum, against all five South African biotypes of Diuraphis noxia (Russian wheat aphid, RWA). Transcript level knockdown of the stripe rust resistance homologue of TaAdnr1, YrU1,/i> from the diploid wheat T. urartu,/i>, was shown to compromise the plant’s resistance response to Puccinia striiformis f. sp. tritici (stripe rust, Pst). To identify if a link exists between both pest and pathogen recognition by TaAdnr1, Gamtoos R containing both Pst and D. noxia resistance was studied. Preliminary results indicate that VIGS-mediated (virus-induced gene silencing) knockdown of TaAdnr1 in the typical Dn7-based resistance, exhibited a susceptible phenotype in D. noxia infestation as well as rust infections with P. striiformis, P. triticina (leaf rust, Pt) and P. graminis f. sp. tritici (stem rust, Pgt). These findings suggest that TaAdnr1 underlies resistance to the South African D. noxia biotypes as well as the three known virulent wheat rust pathogen races in Dn7-mediated resistance in wheat. This raises the possibility that TaAdnr1 recognises effectors from both aphids and pathogens during activation of a resistance response.