ARS | Publication request: The concurrence of Stagonospora nodorum blotch resistance with host-selective toxin insensitivity in tetraploid wheat

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 27, 2008
Publication Date: December 4, 2008
Citation: Chu, C., Friesen, T.L., Chao, S., Faris, J.D., Xu, S.S. 2008. The concurrence of Stagonospora nodorum blotch resistance with host-selective toxin insensitivity in tetraploid wheat. National Wheat Genomics Conference. p. 9 (NWGC), December 4-6, 2008, Indianapolis, IN

Technical Abstract: Resistance to Stagonospora nodorum blotch (SNB) in hexaploid wheat (Triticum aestivum L.) is associated with insensitivity to host-selective toxins (HSTs) produced by the pathogen. In this research, we evaluated the association between HST insensitivity and SNB resistance in tetraploid wheat (T. turgidum L.). From two natural populations that consisted of 172 wild emmer (T. dicoccoides) accessions and 206 cultivated tetraploid wheat accessions including T. carthlicum, T. polonicum, T. turgidum, T. dicoccum and T. turanicum, the associations between SNB resistance and HSTs insensitivity were 43% and 30%, respectively. To further investigate the correlation between SNB resistance and insensitivity to specific HSTs, a doubled haploid (DH) population consisting of 146 lines was developed from the cross between the SNB susceptible durum cultivar Lebsock and the SNB resistant T. carthlicum accession PI 94749. The whole genome map constructed based on this DH population spanned 2036.7 cM and consisted of 283 markers that covered all 14 chromosomes from the A and the B genomes. We inoculated the population with the S. nodorum isolates Sn2000 and Sn4 to evaluate the development of SNB. We also infiltrated the population with the purified HSTs SnToxA and SnTox3, and with crude culture filtrate from isolates Sn4 and Sn2000KO6-1 (a mutant derived from Sn2000 with a disrupted ToxA gene) to evaluate reaction to the HSTs and identify corresponding host genes conferring sensitivity. QTL analysis revealed that genomic regions on chromosome arms 2BS, 4BS and 5BL governed resistance to isolate Sn2000, and loci on chromosome arms 2BS, 3AS, 5BS and 5BL conferred resistance to isolate Sn4. The effects of the 5BS and 5BL QTLs were due to the underlying toxin sensitivity loci Snn3 and Tsn1, which confer sensitivity to the previously characterized toxins SnTox3 and SnToxA, respectively. There was no evidence for a host-toxin interaction associated with the 3AS QTL, but the effects of the 2BS and 4BS QTLs were due to novel host-toxin interactions that have not been previously reported. Therefore, these results led to the identification of two new S. nodorum HSTs and their corresponding host sensitivity genes, and they demonstrate that these novel host-toxin interactions, along with previously characterized host-toxin interactions, play important roles in the development of SNB in this population. This research indicates that host-toxin interactions in the wheat-S. nodorum pathosystem are major disease conferring factors in tetraploid wheat, just as they are in hexaploid wheat.