Mass spectrometry-based metabolomic discrimination of Cercospora leaf spot resistant and susceptible sugar beet germplasms

Authors: HEIDARI, BAHRAM - Shiraz University; MIRAS MORENO, MARIA BEGONA - Università Cattolica Del Sacro Cuore; LUCINI, LUIGI - Università Cattolica Del Sacro Cuore; Bolton, Melvin; McGrath, Jon; BROCCANELLO, CHIARA - Universita Di Padova; ALBERTI, ILARIA - Crea; SELLA, LUCA - Universita Di Padova; CONCHERI, GIUSEPPE - Universita Di Padova; STEVANATO, PIERGIORGIO - Universita Di Padova

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2019
Publication Date: 1/19/2019
Citation: Heidari, B., Miras Moreno, M., Lucini, L., Bolton, M.D., McGrath, J.M., Broccanello, C., Alberti, I., Sella, L., Concheri, G., Stevanato, P. 2019. Mass spectrometry-based metabolomic discrimination of Cercospora leaf spot resistant and susceptible sugar beet germplasms. Euphytica. 215:25. https://doi.org/10.1007/s10681-019-2351-3.
DOI: https://doi.org/10.1007/s10681-019-2351-3

Interpretive Summary: Cercospora leaf spot is a perennial disease problem for sugar beet growers worldwide. Efforts to control the disease with fungicides often become ineffective over time as the pathogen develops resistance to previously effective treatments. Efforts to control the disease through breeding genetic resistance have been effective, but the genetics are poorly understood and widely deploying high levels of leaf spot resistance has met with numerous challenges since it is not a simple genetic system. In this work, metabolites from resistant and susceptible sugar beets were compared, and more than a dozen metabolites were identified as being in one type or the other. These described metabolites may be used as genetic markers to screen additional sugar beets for leaf spot reaction, as well as better describe the genetic basis for leaf spot resistance.

Technical Abstract: A better understanding of the plant metabolites produced in response to disease infection may be useful for the development of disease-resistant crop varieties. In the present study, ultra high-perfor- mance liquid chromatography coupled to quadrupole- time-of-flight mass spectrometry (QTOF-MS) was used to identify differentially accumulated metabo- lites in a subset of sugar beet genotypes harbouring different levels of resistance to Cercospora leaf spot (CLS), a disease caused by the fungal pathogen Cercospora beticola. Leaves of three susceptible (S1, S2 and S3) and two resistant (R1 and R2) genotypes were subjected to QTOF-MS for metabolite profiling. A wide range of metabolites was identified in sugar beet genotypes using metabolomics. Results of Partial Least Squares-Discriminant Analysis indi- cated that 15 metabolites could better discriminate resistant and susceptible genotypes. A Volcano Plot analysis indicated that the flavonoid quercetin 3-O- (600-O-p-coumaroyl)-glucoside and gibberellin A51 with the highest absolute fold change (FC = 16), were repressed in resistant samples. Among the 3 metabo- lites (isovitexin-7-O-xyloside, 3-demethylubiquinol-8 and apigenin 7-O-D-glucoside) showing significant up accumulation in CLS-resistant samples, the flavonoid isovitexin-7-O-xyloside (FC = 4825.634) is associ- ated with resistance to infection with fungal species causing the disease in other crops. Although further studies are still necessary to better elucidate the mechanism of resistance, our results suggest that breeders might exclude susceptible plants based on discriminating metabolites without the need for field inoculation tests. The results also create a solid basis for metabolite-associated reverse genetics and single nucleotide polymorphism discovery based on signif- icantly differentially accumulated metabolites, whose identification is a next strategic priority. The results obtained also underline the role of metabolic signature in CLS resistance mechanisms and provide a platform for the metabolic engineering of sugar beet with higher resistance against C. beticola pathogen.