Sweet Immunity: The Effect of Exogenous Fructans on the Susceptibility of Apple ( Malus × domestica Borkh.) to Venturia inaequalis

• Published in: International journal of molecular sciences Vol. 21; no. 16; p. 5885
• Main Authors: Svara, Anze, Tarkowski, Łukasz Paweł, Janse van Rensburg, Henry Christopher, Deleye, Evelien, Vaerten, Jarl, De Storme, Nico, Keulemans, Wannes, Van den Ende, Wim
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 16-08-2020; MDPI
• Subjects: Aluminum; Antifungal Agents - pharmacology; apple; Biochemistry, Molecular Biology; Carbohydrates; Cultivars; Deoxyribonucleic acid; Disease; Disease Resistance; DNA; Fructans; Fructans - pharmacology; Fungal Genus Venturia - drug effects; Fungal Genus Venturia - pathogenicity; Fungal Genus Venturia - physiology; Fungicides; Infections; Inulin; Leaves; Levan; Levans; Life Sciences; Malus; Malus - drug effects; Malus - immunology; Malus - microbiology; Malus domestica; Metabolism; Mycelia; Ontogeny; Orchards; Pathogens; Pesticides; Plant Leaves - drug effects; Plant Leaves - immunology; Plant Leaves - parasitology; Plant resistance; Potassium; Scab; Seedlings; Signs and symptoms; Spores, Fungal - drug effects; Spores, Fungal - physiology; Sporulation; Spraying; Sugar; Vegetal Biology; Venturia; Venturia inaequalis; apple; priming; fructans; Venturia; leaves; scab; fungicides; Malus; biocontrol
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms21165885

There is an urgent need for novel, efficient and environmentally friendly strategies to control apple scab (
), for the purpose of reducing overall pesticide use. Fructans are recently emerging as promising "priming" compounds, standing out for their safety and low production costs. The objective of this work was to test a fructan-triggered defense in the leaves of apple seedlings. It was demonstrated that exogenous leaf spraying can reduce the development of apple scab disease symptoms. When evaluated macroscopically and by
-specific qPCR, levan-treated leaves showed a significant reduction of sporulation and
DNA in comparison to mock- and inulin-treated leaves, comparable to the levels in fosetyl-aluminum-treated leaves. Furthermore, we observed a significant reduction of
mycelial growth of
on plates supplemented with levans when compared to controls, indicating a direct inhibition of fungal growth. Variations in endogenous sugar contents in the leaves were followed during priming and subsequent infection, revealing complex dynamics as a function of time and leaf ontogeny. Our data are discussed in view of the present theories on sugar signaling and fructan-based immunity, identifying areas for future research and highlighting the potential use of fructans in apple scab management in orchards.