Independent Preharvest Applications of Methyl Jasmonate and Chitosan Elicit Differential Upregulation of Defense-Related Genes with Reduced Incidence of Gray Mold Decay during Postharvest Storage of Fragaria chiloensis Fruit

Abstract

The Chilean strawberry (Fragaria chiloensis) fruit has interesting organoleptic properties, but its postharvest life is affected by gray mold decay caused by Botrytis cinerea. The effect of preharvest applications of methyl jasmonate (MeJA) or chitosan on the molecular defense-related responses and protection against gray mold decay were investigated in Chilean strawberry fruit during postharvest storage. Specifically, we inoculated harvested fruit with B. cinerea spores and studied the expression of genes encoding for the pathogenesis-related (PR) proteins β-1,3-glucanases (FcBG2-1, FcBG2-2 and FcBG2-3) and chitinases (FcCHI2-2 and FcCHI3-1), and for polygalacturonase inhibiting proteins (FcPGIP1 and FcPGIP2) at 0, 2, 24, 48, and 72 h post inoculation (hpi). Remarkably, MeJA- and chitosan-treated fruit exhibited a lower incidence of B. cinerea infection than the control-treated at 48 and 72 hpi. At the molecular level, both are efficient elicitors for priming in F. chiloensis fruit since we observed an upregulation of the FcBG2-1, FcBG2-3, FcPGIP1, and FcPGIP2 at 0 hpi. Moreover, a chitosan-mediated upregulation of FcPGIPs at early times post inoculation (2–24 hpi) and MeJA upregulated FcBGs (24–72 hpi) and FcPGIP1 at later times could contribute to reduce B. cinerea incidence by differential upregulation of defense genes. We concluded that preharvest applications of MeJA or chitosan had a long-lasting effect on the reduction of B. cinerea incidence during postharvest as well as an enhancer effect on the induction of PR and PGIP gene expression.

Grey mould of strawberry, a devastating disease caused by the ubiquitous necrotrophic fungal pathogen Botrytis cinerea

“…In strawberry, JA appears to be involved in defence responses against B. cinerea . For example, strawberries treated with MeJA had a delayed and much slower progression of B. cinerea infections (Saavedra et al , ; Zhang et al , ).…”

Induced and primed defence responses of Fragaria vesca to Botrytis cinerea infection

“…However, no visible necroses was observed in F. vesca plants upon spray treatment of chemicals or the mock treatment. Also, there are reports of spray treating strawberry plants with different chemicals to study induced resistance (Terry and Joyce, 2000;Eikemo, Stensvand and Tronsmo, 2003;Hukkanen et al, 2007;Landi et al, 2017;Saavedra et al, 2017). We therefore consider the observed effects to be the plant's induced responses to priming agent treatments.…”

“…Sigma-Aldrich, #A44207-5G), R-β-homoserine (RBH, Aurum Pharmatech, #S-4676), and prohexadione-calcium (ProCa, Sigma, #31720) were dissolved in distilled H 2 O, methyl jasmonate (MeJ, Sigma-Aldrich, #392707) was prepared in 0.1% Tween-20, and gibberellic acid (GA3, Duchefa, #G0907.0001) was first dissolved in 50 µl ethanol and then diluted in H 2 O. Plants were treated in three different ways: (i) soil-drench using ten times concentrated (10×) solutions of the priming chemical(Jakab et al, 2005;Wilkinson et al, 2018), (ii) spray treatment of above-ground parts using final concentration (1×) chemical solutions(Saavedra et al, 2017), and (iii) treatment of seeds. For soil-drench treatments, 10× solutions were prepared corresponding to the concentrations given in the figure legends.Plants were treated by pouring 10% of the pot volume of the 10× solution into each pot.…”

<i>n</i>-Propyl dihydrojasmonates influence ethylene signal transduction in infected apple fruit by <i>Botrytis cinerea</i>

“…Other research showed that preharvest methyl jasmonate application reduced growth infection of B. cinerea in Chilean strawberries [F. chiloensis (L.) Mill.] through upregulation of the β-1,3-glucanase gene (FcBGs) and polygalacturonaseinhibiting protein (FcPGIP) gene (Saavedra et al, 2017). JA is associated with defense mechanisms against Alternaria altemata, Pseudomonas syringae, Hort.…”