First report of the production of palmarumycins and other secondary metabolites by Lasiodiplodia exigua from Retama raetam showing cankers and dieback

Eight secondary metabolites including a new palmarumycin, exiguospirone (1), were isolated from mycelial and culture filtrate extracts of a selected strain (ex-type culture BL104) of Lasiodiplodia exigua Linaldeddu, Deidda & A.J.L. Phillips isolated in Tunisia from retem plants (Retama raetam (Forsskål) Webb & Berthelot) showing cankers and a progressive dieback of branches. Compounds obtained in enough quantities (i.e. palmarumycin JC2, nigrosphaerilactone, lasiolactols, (R)-mellein, (3R,4R)-4-hydroxymellein and (3R,4S)-4-hydroxymellein) have been tested in hypocotyl and radicle elongation bioassays on Portulaca oleracea L. At concentrations of 1.45–5.81 mM, lasiolactols and isocoumarins significantly inhibited hypocotyl and radicle elongation with a dose-response trend.