Occurrence, isolation and biological activity of phytotoxic metabolites produced in vitro by Sphaeropsis sapinea, pathogenic fungus of Pinus radiata

Abstract

Sphaeropsis sapinea was repeatedly isolated in Sardinia from symptomatic samples of the upper part of declining pine (Pinus radiata) plants. Observed symptoms mainly consisted of foliage chlorosis, drying of needles and cankers on branches. The S. sapinea strains were shown to produce phytotoxic metabolites in culture filtrates. Three metabolites were isolated for the first time from this fungus and identified by their spectroscopic and optical properties as R-())-mellein, (3R,4R)-4-hydroxymellein and (3R,4S)-4-hydroxymellein. When assayed for phytotoxic and antifungal activities on host and non-host plants and on some phytopathogenic fungi, the R-())-mellein showed significant activity, while the other two 3,4-dihydroisocoumarins showed only a synergic activity in both tests.

An In Planta -Expressed Polyketide Synthase Produces ( R )-Mellein in the Wheat Pathogen Parastagonospora nodorum

“…Above all, the most commonly reported bioactivity of mellein and its derivatives is their non-host-specific toxicity against plants. (R)-Mellein and hydroxymelleins have been isolated as phytotoxins of the apple and grapevine pathogen Botryosphaeria obtusa (53,65), the pine pathogen S. sapinea (57), the citrus pathogen Phoma tracheiphila (54), and the grapevine canker agent N. parvum (39). It has also been shown to induce phytotoxic symptoms on tomato cuttings when it is used at 100 g/ml (54) and causes necrosis on detached grape (Vitis vinifera) leaf at concentrations as low as 3 g/ml (65).…”

“…In addition, it has been observed that mellein slows the cell cycle, with the cell having an extended mitotic phase (68). Interestingly, the biological sources of (R)-mellein are overrepresented in fungal plant pathogens (39,53,54,57,65) and endophytes (51,52,58,59). Whether mellein plays a role in this plant-fungus interaction and why SN477 is strongly upregulated in planta are questions that warrant future investigation.…”

Extracellular compounds produced by fungi associated with Botryosphaeria dieback induce differential defence gene expression patterns and necrosis in Vitis vinifera cv. Chardonnay cells

“…Mellein and its derivatives are not produced by esca-associated pathogens such as Pal, Pch and Fme (Djoukeng et al 2009). Mellein was the cause of frogeye leaf spot and black rot of apple (Venkatasubbaiah et al 1990 and1991) and was also produced by D. pinea, another Botryosphaeriaceae species, and caused the decline of Pinus radiata in Italy (Cabras et al 2006). However, mellein and its derivatives seem not to be produced exclusively by botryosphaeriaceous fungi, given that other studies have also associated these compounds with non-botryosphaeriaceous fungi such as the genera Phoma, Pezicula, Septoria, Sphaeropsis and Xylaria (Cabras et al 2006;Turner and Aldridge 1983).…”

Phytotoxic metabolites from Neofusicoccum parvum, a pathogen of Botryosphaeria dieback of grapevine

“…Dihydroisocoumarins have been isolated from several fungi, including species from the Aspergillus, Cercospora, Cryptosporiopsis, Hypoxylon, Phoma, and Xylaria genera (the list is not exhaustive) with phytotoxic, zootoxic and moderate antifungal activities (Turner and Aldridge, 1983;Cabras et al, 2006). Compounds 8, 9 and 10 were isolated from N. parvum (Evidente et al, 2010) with 7-hydroxymellein and 4,7-dihydroxymellein, which are phytotoxins produced by (D. seriata) B. obtusa from grapevine (Djoukeng et al, 2009).…”