High Chlorogenic and Neochlorogenic Acid Levels in Immature Peaches Reduce Monilinia laxa Infection by Interfering with Fungal Melanin Biosynthesis

Abstract

Chlorogenic acid (CGA) and its isomer, neochlorogenic acid (NCGA), were found to be the major phenolic compounds in the flesh and peel of three peach cultivars. Their concentrations are especially high in immature fruits (CGA, 151-548 mg/kg; NCGA, 85-380 mg/kg), whose resistance to the brown rot fungus, Monilinia laxa , is very high. The concentrations of these two phenolic compounds decline in maturing fruits (CGA, 77-181 mg/kg; NCGA, 30-82 mg/kg), and this decline is associated with a concomitant increase in susceptibility to brown rot infection. Other phenolic compounds found in the same HPLC chromatograms at 340 nm from each peach extract at varying sampling dates in each of the three peach cultivars were not correlated with the incidence of brown rot and appeared only in some cultivars. The incidence of brown rot for each cultivar at each sampling date was significantly negatively correlated with the NCGA (r > -0.85) and CGA (r > -0.90) contents. At concentrations that are similar to those in peach fruit, CGA does not inhibit spore germination or mycelial growth of M. laxa in culture but markedly inhibits the production of melanin-like pigments in the mycelia of M. laxa in culture (42% melanin reduction). Accordingly, we propose that the high concentrations of CGA and NGA in immature fruits might contribute to their reduced susceptibility or increased resistance to brown rot infection by interfering with fungal melanin production.

QTL mapping for brown rot (Monilinia fructigena) resistance in an intraspecific peach (Prunus persica L. Batsch) F1 progeny

“…BR resistance decreases in stone fruit between pit hardening and physiological maturity (Biggs and Northover 1988;Mari et al 2003). This change has been suggested to be due to a concomitant drop in the fruit phenolic content Bostock 2006, 2007;Villarino et al 2011). Based on our's and previous results, the relationship between MD and flesh BR resistance in C×EL may be linked to varying decay of fruit barriers during the ripening process.…”

“…In a previous study (Pascal et al 1994), skin-and flesh-associated resistance were not correlated in diverse stone fruit species. Biochemical effectors related to BR resistance have been described in stone fruits, such as pathogenesis-related proteins PR-5 and PR-10 in European plum (Prunus domestica;El-kereamy et al 2009;El-Kereamy et al 2011) and the antifungal activities of caffeic acid and chlorogenic acid on peach (Bostock et al 1999;Lee and Bostock 2007;Villarino et al 2011). Recently, MartinezGarcia et al (2013a) reported a first study to associate specific regions of Prunus genome with BR resistance phenotype by QTL analysis, with crosses between peach canning, nonmelting cultivars, and peach×almond interspecific hybrids.…”

Fruit maturity and post-harvest environmental conditions influence the pre-penetration stages of Monilinia infections in peaches

“…Most studies on appressorial formation by M. fructicola have focused on the surface properties of the fruit, the stage of fruit maturity, and the signaling pathways that are required for surface attachment and appressorial formation (Cruickshank and Wade, 1992;Lee and Bostock, 2006). The incidence of brown rot increases as fruit approaches maturity (Gell et al, 2008;Lee and Bostock, 2007;Villarino et al, 2011): immature fruit are more resistant to infection than mature fruit (Gell et al, 2008;Bostock, 2006, 2007;Xu et al, 2007).…”

“…The matrix glycans in the walls of peach mesocarp cells are gradually depolymerized and the polymers are deglycosylated during maturation, and the chelator-soluble polyuronides are solubilized and depolymerized after the initiation of ripening (Brummell et al, 2004). Villarino et al (2011) reported that the susceptibility of peaches to M. laxa infection was greatest when the pericarp was completely formed, and the concentrations of chlorogenic and neochlorogenic acid in the pericarp are low. Melanin production by M. laxa is inhibited when the concentrations of chlorogenic and neochlorogenic acid in the pericarp are high and melanin is essential for penetration of the pericarp by Monilinia spp.…”

“…Melanin production by M. laxa is inhibited when the concentrations of chlorogenic and neochlorogenic acid in the pericarp are high and melanin is essential for penetration of the pericarp by Monilinia spp. (Villarino et al, 2011). The presence of phenolic acids, such as chlorogenic and caffeic acids can inhibit the cutinase and polygalacturonase activity of M. fructicola in immature nectarines and peaches.…”