Polyketide Derivatives in the Resistance of Gerbera hybrida to Powdery Mildew.

Anna Mascellani,Petr Marsik,Jan Tauchen,Jaroslav Havlik,Milan Malanik,Estuardo Hernandez Olesinski,Kirsten Leiss,Pavel Kloucek,Johanna Bac-Molenaar,Karel Smejkal

doi:10.3389/fpls.2021.790907

Abstract

Powdery mildew is a common disease affecting the commercial production of gerbera flowers (Gerbera hybrida, Asteraceae). Some varieties show a certain degree of resistance to it. Our objective was to identify biomarkers of resistance to powdery mildew using an 1H nuclear magnetic resonance spectroscopy and chemometrics approach in a complex, fully factorial experiment to suggest a target for selection and breeding. Resistant varieties were found to differ from those that were susceptible in the metabolites of the polyketide pathway, such as gerberin, parasorboside, and gerberinside. A new compound probably involved in resistance, 5-hydroxyhexanoic acid 3-O-β-D-glucoside, was described for the first time. A decision tree model was built to distinguish resistant varieties, with an accuracy of 57.7%, sensitivity of 72%, and specificity of 44.44% in an independent test. Our results suggest the mechanism of resistance to powdery mildew in gerbera and provide a potential tool for resistance screening in breeding programs.

Highlights

Plants as sessile organisms cannot escape from unfavorable conditions in their surroundings
Discriminating analysis of resistant and susceptible gerbera plants showed that gerberin, parasorboside, gerberinside, and 5-hydroxyhexanoic acid 3-O-β-D-glucoside can be used as biomarkers for resistance to powdery mildew
Independent of leaf age, these compounds showed greater concentrations in the resistant compared to the susceptible varieties. These polyketide-derived glycosylated molecules are compounds wellknown present in gerbera (Bohlmann et al, 1973; Teeri et al, 2006), where the aglycones are considered to play a role in defending the plant against pathogens (Koskela et al, 2001, 2011; Pietiäinen et al, 2016)

Summary

Introduction

Plants as sessile organisms cannot escape from unfavorable conditions in their surroundings For this reason, they have acquired the ability to produce a remarkable diversity of low-molecularweight compounds to protect themselves. They have acquired the ability to produce a remarkable diversity of low-molecularweight compounds to protect themselves They produce a vast range of so-called secondary metabolites, adapted to combat exposure to pathogens or herbivores both above and below the ground (Pichersky and Gang, 2000; Sirikantaramas et al, 2008). Those defensive compounds are subjected to changes as the plant continues to evolve and adapt. More than one compound is usually involved in such biological processes, providing additional if not synergistic effects and reducing the chance that pathogens and herbivores might develop resistance

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