Mapping non-host resistance to the stem rust pathogen in an interspecific barberry hybrid

Authors: BARTAULA, RADHIKA - University Of New Hampshire; MELO, ARTHUR - University Of New Hampshire; KINGAN, SARAH - Pacific Biosciences Inc; Jin, Yue; HALE, IAGO - University Of New Hampshire

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2019
Publication Date: 7/16/2019
Citation: Bartaula, R., Melo, A.T., Kingan, S., Jin, Y., Hale, I. 2019. Mapping non-host resistance to the stem rust pathogen in an interspecific barberry hybrid. Biomed Central (BMC) Plant Biology. 19:319. https://doi.org/10.1186/s12870-019-1893-9.
DOI: https://doi.org/10.1186/s12870-019-1893-9

Interpretive Summary: The use of non-host resistance (NHR) to plant diseases presents a compelling long-term plant protection strategy for global food security, yet the genetic basis of NHR remains poorly understood. For many plant diseases, including stem rust of wheat, NHR is largely unexplored due to the inherent challenge of developing a genetically tractable system within which the resistance segregates. In this study, an interspecific mapping population derived from a cross between stem rust resistant Japanese barberry and stem rust susceptible common barberry was developed to investigate the putative NHR exhibited by Japanese barberry. The first genetic linkage maps for the two parental species were constructed, and a chromosome-scale reference genome for Japanese barberry was assembled. QTL analysis resulted in the identification of a single genomic region associated with resistance. Differential gene expression analysis, combined with sequence variation analysis between the two parental species, led to the prioritization of several candidate genes within that region, some of which belong to gene families previously implicated in disease resistance. Through this research, publicly- available foundational genetic and genomic resources were developed for the barberry-stem rust pathosystem. Although subsequent validation and fine mapping studies are needed, this study demonstrates the feasibility of and lays the groundwork for dissecting NHR to stem rust in the alternate host of one of agriculture's most devastating pathogens. These research findings will be highly valuable for scientists who are developing long-term strategies for disease control.

Technical Abstract: Non-host resistance (NHR) presents a compelling long-term plant protection strategy for global food security, yet the genetic basis of NHR remains poorly understood. For many diseases, including stem rust of wheat [causal organism Puccinia graminis (Pg)], NHR is largely unexplored due to the inherent challenge of developing a genetically tractable system within which the resistance segregates. In this study, an interspecific mapping population derived from a cross between Pg-resistant Berberis thunbergii (Bt) and Pg-susceptible B. vulgaris was developed to investigate the Pg-NHR exhibited by Bt. To facilitate QTL analysis and subsequent trait dissection, the first genetic linkage maps for the two parental species were constructed and a chromosome-scale reference genome for Bt was assembled (PacBio + Hi-C). QTL analysis resulted in the identification of a single 13 cM region (~5.1 Mbp spanning 13 physical contigs) on the short arm of Bt chromosome 3. Differential gene expression analysis, combined with sequence variation analysis between the two parental species, led to the prioritization of several candidate genes within the QTL region, some of which belong to gene families previously implicated in disease resistance. Foundational genetic and genomic resources developed for Berberis spp. enabled the identification and annotation of a QTL associated with Pg-NHR. Although subsequent validation and fine mapping studies are needed, this study demonstrates the feasibility of and lays the groundwork for dissecting Pg-NHR in the alternate host of one of agriculture's most devastating pathogens.