Abstract: This study was intended to clarify the effect of hydroxyoctadecaenoic acid (HODE) on the spore production and ochratoxin A (OTA) synthesis of Aspergillus ochraceus at different population densities. Here we measured the yields of 9S-HODE, 13S-HODE and OTA during the culture process of A. ochraceus, and we also determined the production of spores and OTA after adding 9S-hydroxy-10E,12Z-octadecadienoic acid (9S-HODE) or 13S-hydroxy-9Z,11E-octadecadienoic acid (13S-HODE) and the infection degree of grain seeds with different densities of A. ochraceus. The results showed that the ratio of 9S-HODE/13S-HODE and the yield of OTA were higher at lower inoculation density (103 spores/mL); the addition of 9S-HODE inhibited the sporulation of A. ochraceus and promoted OTA synthesis, while 13S-HODE just had the opposite effect. After infection with A. ochraceus at initial spore density of 103 and 106 spores/mL, the germination rates of peanut, soybean, corn and wheat were reduced by 29%, 21%, 17% and 14%; and by 35%, 29%, 20% and 22%, respectively. These findings indicated that the population density of A. ochraceus could affect 9S-HODE, 13S-HODE and OTA production. 9S-HODE and 13S-HODE may both be A. ochraceus quorum sensing signal molecules, which had opposite effects on A. ochraceus spore production and OTA synthesis. High population density of A. ochraceus was more infectious to grain seeds. Seeds with high levels of fat and protein content were more susceptible to A. ochraceus.

Key words: hydroxyoctadecaenoic acids, oxylipins, ochratoxin A, quorum sensing, Aspergillus ochraceus