Effects of temperature, water activity, and fungal isolate on ochratoxin A accumulation in oat grain inoculated with Penicillium verrucosum and development of a methodology to screen oat cultivars for ochratoxin A accumulation

Abstract

Background and objectives Ochratoxin A (OTA) is one of the most prevalent mycotoxins in cereal grains. In temperate climates, Penicillium verrucosum is the primary OTA producer. Our objectives were (a) to determine the effects of various factors on OTA accumulation in oat grain inoculated with P. verrucosum and (b) to develop a method to screen oat cultivars for OTA accumulation. Findings Grain samples from three oat cultivars were inoculated with three different isolates of P. verrucosum, incubated at two water activity levels (0.85 and 0.90 aw) and two temperatures (22.5 and 27.5°C) for 4, 7, and 10 weeks. A water activity of 0.90 and a temperature of 22.5°C provided the highest level of OTA accumulation. Isolate C1136‐1 was the highest OTA producer among the isolates of P. verrucosum studied. The longer the incubation period, the higher the OTA accumulation in oat grain samples was. Conclusions The P. verrucosum isolate, the water activity and temperature during incubation, and the incubation period, all had an effect on the level of OTA accumulation. Inoculating grains with isolate C84‐2 and incubating at 22.5°C and 0.90 aw for 7 weeks provided adequate conditions to screen oat cultivars for OTA accumulation. Significance and novelty A new protocol was developed that can be used for discriminating among oat cultivars for level of OTA accumulation. It would ultimately help breeders and pathologists in selecting genotypes with reduced OTA accumulation.

Statistical approach to evaluate effect of temperature and moisture content on the production of antioxidant naphtho-gamma-pyrones and hydroxycinnamic acids by Aspergillus tubingensis in solid-state fermentation

“…The influence of moisture content and temperature is essential in the growth and secondary metabolite production of fungi [5,6]. However, although some tendencies have been described regarding the effects of moisture content and temperature on secondary metabolism, each fungal strain has its own behavior when facing environmental conditions changes [7,8]. It is, therefore, important to empirically study those effects when dealing with a strain of industrial interest to optimize the production.…”

Effect of oat cultivar on ochratoxin A accumulation following grain inoculation with Penicillium verrucosum

“…Competition between P. verrucosum and other fungal species such as Aspergillus flavus may inhibit OTA production (Ramakrishna, Lacey, & Smith, ); therefore, all the oat samples were sterilized with gamma irradiation prior to inoculation with P. verrucosum strain C84‐2. Following inoculation, samples were incubated in humidity chambers maintained at a relative humidity of 90% using a saturated salt solution of CaCl 2 and a temperature of 22.5°C to promote an environment favorable to OTA production (Dhungana et al, ).…”

“…A seven‐day‐old culture of a OTA producing strain (C84‐2) of P . verrucosum in DYSG media was used to inoculate gamma irradiated oat samples (30 g) by spraying 4 ml of spore suspension (Dhungana et al, ). Sterile water (amount calculated from moisture adsorption curve) was added to adjust inoculated grain samples to 0.90 a w .…”

“…It is not clear whether different oat genotypes also respond differently to infection with P. verrucosum (Dhungana et al, ), and if so, how grain characteristics and grain composition affect OTA accumulation. Oats contain avenanthramides, a phenolic antioxidant that exhibit antimicrobial activity (Wise, ).…”