Title: An exploratory study on the fungal agents of storage rots on organically grown apples in Flanders
Authors: Naets, Matthias
Dams, Stan
Deslypere, Mathias
Verstreken, Heleen
Van Riet, Stefanie
Keulemans, Wannes
Van Hemelrijck, Wendy
Geeraerd, Annemie
Issue Date: 15-Sep-2016
Conference: Twenty-first Conference on Food Microbiology edition:21 location:Brussels (Belgium) date:15-16 September 2016
Abstract: Introduction.
Because of increasing societal worries about the impact of synthetic pesticides on human health and envi¬ron-ment, organic farming has been gaining in market share. Still, important economic losses are frequently observed due to fungal pathogens. For apple, as much as 60 % of the harvest can be lost due to fungal infections [1]. Therefore, the goal of this work was to investigate which fungal pathogens are associated with storage losses for organically grown apples. Also ripening parameters were measured to investigate correlations with prevailing pathogens, cultivars or maturity stage.
Material and methods.
Organically grown apples with visible rot symptoms were obtained directly from participating growers and auctions after 4-5 months of ultra low oxygen storage. Six batches, each consisting of 30 visibly infected apples and 16 unaffected apples were examined. There were 3 batches of Jonagold and one of Jonagored, Topaz and Elstar. Jonagold, Jonagored and Topaz are the main produced organic cultivars in Flanders. Infections were isolated on solid medium (167 mL apple juice, 1.67 g CaCO3, 6.25 g agar, 6.25 g PDA, 833 mL dH2O). Identification was performed based on macro¬scopic and microscopic morphology. Ripening para¬meters were determined for the unaffected fruit: respiration rate (RO2), ethylene production rate (RETH), firmness, total soluble solids (TSS) and hue angle.
All affected apples investigated contained Penicillium expansum. Neofabraea was found on Jonagored, Elstar and Topaz, but not on any of the Jonagold apples. Botrytis cinerea and Monilinia fructigena were found only on Jonagold. Fusarium, Mucor, Phytophthora and Neonectria were also encountered, but could not be identified with certainty due to inconsistency between the different determination levels.
Interestingly, although the Jonagored apples were more mature (higher RO2, RETH, TSS and lower firmness) than the Jonagold apples, we did not find any Botrytis cinerea on Jonagored apples while we did on Jonagold. This contrasts with the fact that fruit maturation is known to increase susceptibility to B. cinerea [2]. Jonagored is a color mutant of Jonagold that has a more intense red color. This could explain this contradiction, because anthocyanin content has been found to negatively correlate with susceptibility [3], because anthocyanins can act as antioxidants and one of the attack strategies of B. cinerea consists in disturbing redox processes in the fruit [4]. Neofabraea was found on all cultivars except for Jonagold. The Jonagold apples had the highest firmness, which might be related to differences in cell wall structure.
[1]Wenneker et al. (2015).
[2]Dean R. et al. (2012). Molecular Plant Pathology 13(4): 414-430.
[3]Zhang Y. et al. (2013). Current Biology 23(12): 1094-1100.
[4]Lyon G. D. et al. (2004). In Botrytis: Biology, Pathology and Control. 119-141.
Publication status: accepted
KU Leuven publication type: AMa
Appears in Collections:Division of Crop Biotechnics
Division of Mechatronics, Biostatistics and Sensors (MeBioS)

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