title: Acidification of apple and orange hosts by Penicillium digitatum and Penicillium expansum.
abstract: New information about virulence mechanisms of Penicillium digitatum and Penicillium expansum could be an important avenue to control fungal diseases. In this study, the ability of P. digitatum and P. expansum to enhance their virulence by locally modulating the pH of oranges and apples was evaluated. For each host, pH changes with a compatible pathogen and a non-host pathogen were recorded, and the levels of different organic acids were evaluated to establish possible relationships with host pH modifications. Moreover, fruits were harvested at three maturity stages to determine whether fruit maturity could affect the pathogens' virulence. The pH of oranges and apples decreased when the compatible pathogens (P. digitatum and P. expansum, respectively) decayed the fruit. The main organic acid detected in P. digitatum-decayed oranges was galacturonic acid produced as a consequence of host maceration in the rot development process. However, the obtained results showed that this acid was not responsible for the pH decrease in decayed orange tissue. The mixture of malic and citric acids could at least contribute to the acidification of P. digitatum-decayed oranges. The pH decrease in P. expansum decayed apples is related to the accumulation of gluconic and fumaric acids. The pH of oranges and apples was not affected when the non-host pathogen was not able to macerate the tissues. However, different organic acid contents were detected in comparison to healthy tissues. The main organic acids detected in P. expansum-oranges were oxalic and gluconic and in P. digitatum-apples were citric, gluconic and galacturonic. Further research is needed to identify the pathogenicity factors of both fungi because the contribution of organic acids has profound implications.
authors.affiliation: IRTA, XaRTA-Postharvest, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Vilanova
authors.affiliation: Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Viñas
authors.affiliation: IRTA, XaRTA-Postharvest, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Torres
authors.affiliation: IRTA, XaRTA-Postharvest, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Usall
authors.affiliation: Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Buron-Moles
authors.affiliation: IRTA, XaRTA-Postharvest, Rovira Roure 191, 25198 Lleida, Catalonia, Spain. Electronic address: neus.teixido@irta.cat.
authors.forename: N
authors.initials: N
authors.lastname: Teixidó
mesh_terms: D000143:Acids / Q000032:analysis*; D032084:Citrus sinensis / Q000382:microbiology*; D005516:Food Microbiology; D005638:Fruit / Q000737:chemistry / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D027845:Malus / Q000382:microbiology*; D015999:Multivariate Analysis; D010407:Penicillium / Q000254:growth & development / Q000378:metabolism*; D037521:Virulence Factors / Q000032:analysis
chemical_list: D000143:Acids; D037521:Virulence Factors
keywords: Blue mould; Green mould; Host acidification; Maturity stage; Organic acid; pH