Lasiolactols A and B Produced by the Grapevine Fungal Pathogen Lasiodiplodia mediterranea

Abstract

A strain of Lasiodiplodia mediterranea, a fungus associated with grapevine decline in Sicily, produced several metabolites in liquid medium. Two new dimeric γ‐lactols, lasiolactols A and B (1 and 2), were characterized as (2S*,3S*,4R*,5R*,2′S*,3′S*,4′R*,5′R*)‐ and (2R*,3S*,4R*,5R*,2′R*,3′S*,4′R*,5′R*)‐(5‐(4‐hydroxymethyl‐3,5‐dimethyl‐tetrahydro‐furan‐2‐yloxy)‐2,4‐dimethyl‐tetrahydro‐furan‐3‐yl]‐methanols by IR, 1D‐ and 2D‐NMR, and HR‐ESI‐MS. Other four metabolites were identified as botryosphaeriodiplodin, (5R)‐5‐hydroxylasiodiplodin, (–)‐(1R,2R)‐jasmonic acid, and (–)‐(3S,4R,5R)‐4‐hydroxymethyl‐3,5‐dimethyldihydro‐2‐furanone (3 – 6, resp.). The absolute configuration (R) at hydroxylated secondary C‐atom C(7) was also established for compound 3. The compounds 1 – 3, 5, and 6, tested for their phytotoxic activities to grapevine cv. Inzolia leaves at different concentrations (0.125, 0.25, 0.5, and 1 mg/ml) were phytotoxic and compound 5 showed the highest toxicity. All metabolites did not show in vitro antifungal activity against four plant pathogens.

Fatty Acids Produced by Neofusicoccum vitifusiforme and N. parvum, Fungi Associated with Grapevine Botryosphaeria Dieback

“…The most abundant component identified is linoleic acid (48.2%). Octadecenoid acids have influence in the fungal virulence because many of them are precursors of jasmonic acid [33], a plant hormone capable of inducing phytotoxic effects [12,22,[34][35][36][37]. Furthermore, Farmer and Ryan [38] tested the capacity of octadecenoid precursors of jasmonic acid, such as linolenic acid and linoleic acid (which can be converted to linolenic acid by the plant) to be inducers of proteinase inhibitors in tomato, tobacco, and alfalfa leaves.…”

“…In fact, the relationship between the botryosphaeriaceous fungi found in the diseased wood and the foliar symptoms observed in some declining vines is still not well understood [6] and the presence of these symptoms has been very sporadic in monitored Sicilian vineyards. So much so that the foliar chlorosis was only observed for plants infected by L. mediterranea strain (B6) and not for plants infected by N. parvum (B19), although both produce an assortment of different metabolites [12,13].…”

“…Strains B8 (N. vitifusiforme) and B19 (N. parvum) were isolated from stem cankers of symptomatic grapevines showing subcortical discolourations and xylematic sectorial necrosis, but in both cases without foliar symptoms, in a vineyard in western Sicily and identified in a previous study [12]. The pathogenicity of B19 strain has been reported before [13] while both pathogenicity re-isolation tests of strain B8 were performed on 2-year-old grapevine plants of cv.…”

“…In Sicily, Botryosphaeria dieback has been recently associated with botryosphaeriaceous fungi, such as D. seriata, L. mediterranea, N. vitifusiforme and N. parvum [10,11]. Furthermore, the pathogenicity in planta of some of them (i.e., L. mediterranea and N. parvum) was newly assayed [12,13].…”

“…It was hypothesized that leaf symptoms could depend on phytotoxic metabolites produced by fungi in the xylem, which are moved to the leaves, or induce a chain effect determining the expression of foliar symptoms [15][16][17][18][19][20]. In fact, several pathogens involved in GTDs produce secondary metabolites in vitro and in vivo whose mode of action is sometimes reported [12][13][14][15][16]21,22]. Many secondary metabolites (e.g., cyclohexenones, melleins, naphtalenones, and phenols) were isolated from in vitro culture of diverse species of Neofusicoccum associated with grapevine dieback [9,14,16,18,21], and some of them are reported as vivotoxins [15].…”