Spencertoxin and spencer acid, new phytotoxic derivatives of diacrylic acid and dipyridinbutan-1,4-diol produced by Spencermartinsia viticola, a causal agent of grapevine Botryosphaeria dieback in Australia

Spencermartinsia viticola is one of the most widespread Botryosphaeriaceae species isolated from grapevines in South Australia and New South Wales vineyards in Australia. A new phytotoxic dipyridine-butane-1,4-diol and a new diacrylic acid derivatives, here named spencertoxin (1) and spencer acid (2), were isolated from the culture filtrates of S. viticola isolate DAR78870 together with p-hydroxybenzaldehyde (3) and 2-(4-hydroxyphenyl) acetic acid (4). Spencertoxin and spencer acid were characterized as 2,3-di(pyridin-3-yl)butane-1,4-diol and (2Z,2′Z)-3,3′-(carbonylbis(oxy))diacrylic acid, respectively, by spectroscopic methods (essentially NMR and HRESIMS). Spencertoxin (1), p-hydroxybenzaldehyde (3) and 2-(4-hydroxyphenyl) acetic acid (4) showed phytotoxicity when the pure compounds were assayed on grapevine leaves of Vitis lambrusca and Vitis vinifera cv. Shiraz. Keywords: Grapevine, Botryosphaeria dieback, Spencermartinsia viticola, Phytotoxins, Spencertoxin and spencer acid