Biocontrol Strategies for Effective Kiwifruit Post-Harvest Disease Management

In the early ’90s, the skin-pitting disease was reported in various Italian regions. Initially, its incidence was negligible however, by the year 2000, the percentage of disease was significantly increased (20–30%) in kiwifruit batches coming from the main kiwifruit-producing areas of Italy. For more than a decade, The University of Udine has been dedicated efforts to researching kiwifruit skin-pitting in Friuli Venezia Giulia (FVG) region. The initial focus was on establishing its etiology, followed by the development of diagnostic tools. In 2021, a research was planned with the principal objective of investigating the biological control strategies for the management of this postharvest skin-pitting disease as an eco-friendly approach. Additionally, the study aimed to quantify the population dynamics of causative agent Cadophora luteo-olivacea, from the surface of kiwifruit throughout the growing season. The study has been started by the collection of untreated kiwifruits from four different kiwifruit orchards in Friuli Venezia Giulia (FVG) region followed by weekly monitoring of skin-pitting disease incidence during the postharvest cold storage of these fruits. During this monitoring period, the fungal pathogen C. luteo-olivacea was isolated from the surface of symptomatic kiwifruit tissues and molecularly identified through qPCR. Several biological control organisms, including bacteria, yeast, and fungi, were selected to test their antifungal potential against C. luteo-olivacea through different in vitro and in vivo assays. Among the tested BCAs, Bacillus spp and P. synxantha emerged as the most efficient BCAs and selected to subsequent experiments. To understand the mode of action of these BCAs, an in-depth biochemical analysis was conducted using infrared spectroscopy (FT-IR) that revealed the presence of different antifungal compounds where P. synxantha showed the most intense peaks (at 988 cm−1), correlating with the highest concentration of antifungal compounds. Considerations the potential antagonistic activity of P. synxantha, further biochemical characterization of volatile organic compounds (VOCs) and the effect of single synthetic pure compounds on the mycelial growth of kiwifruit postharvest fungal pathogens, Botrytis cinerea and C. luteo-olivacea was examined. The effect of fruit biofumigation with P. synxantha VOCs on the expression of kiwifruit defense-related genes was also studied. Beyond to postharvest disease management efforts, a comprehensive investigation was conducted into the population dynamics of the fungal pathogen throughout the fruit’s growing season. The study was conducted in four kiwifruit orchards situated in the Friuli Venezia Giulia region. The research also focused on the potential correlation between the pathogen contamination on the fruit surface and the incidence of postharvest skin-pitting disease. This multifaceted thesis holds significant implications for the kiwifruit industry, selecting an effective BCA with high antifungal ability and eco-friendly strategies for the effective management of postharvest skin-pitting disease. Use of antifungal VOCs compounds produced by biological agents in postharvest offers novel approaches for biofumigation and disease control. Additionally, this study also provides a holistic understanding of the pathogen’s behavior from orchard to postharvest.