Mycotoxins and Related Fungi in Italian Paddy Rice During the Growing Season and Storage

Abstract

Mycotoxigenic fungi and relative mycotoxins contamination were monitored in Italian paddy rice samples both in field during the growing season and the first five months of storage. Three experimental fields, nine rice varieties and three sowing densities were considered; then, different lots of paddy rice were stored in warehouses at different temperature regimes. Fusarium spp. and Aspergillus spp. were found to be the fungi most likely to produce mycotoxins throughout the growing season. In particular, A. flavus and A. niger were found only rarely both in field and in post-harvest, while A. versicolor was always present although in low concentrations. Penicillium spp. strains were isolated sporadically and were found to be irrelevant in Italian rice fungal contamination. Sterigmatocystin (STC) was the main mycotoxin found in Italian rice, while aflatoxin (AFB1), deoxynivalenol (DON) and ochratoxin A (OTA) were rarely detected. Contamination generally increased from post-flowering to ripening; considering rice varieties, significant differences (p ≤ 0.01) were found in fungal contamination and STC production; no differences were observed between sowing densities. During storage, an increase in STC content was observed in higher temperature regimes, while all the other considered mycotoxins remained unchanged. These results indicated that contamination by STC, an emerging mycotoxin not legislatively regulated by the European Union, can be relevant in rice.

Efficacy of Azoxystrobin on Mycotoxins and Related Fungi in Italian Paddy Rice

“…Among the considered mycotoxins considered, OTA and AFs were never detected; DON was found in 46% of the samples at levels always lower than 100 µg/kg, while STC occurred in almost all the paddy rice samples, showing a maximum value of 15.5 µg/kg. These data partially accord with a previous study, carried out on rice samples collected in the same area, that found DON and AFs only sporadically and in low amounts, while STC was always detected, appearing as crucial in rice contamination [10].…”

“…The highest DON contamination was found in the rice variety CL15 while the lowest was in the rice variety Centauro (Table 1); none of the rice varieties considered in the study showed a DON contamination above the limits fixed by the European Commission of 1250 µg/Kg for paddy rice (EU Regulation 1881/2006). These results seem to confirm the findings of a previous study where DON was found only in low amounts [10] suggesting that this mycotoxin could be considered a minor risk for Italian paddy rice.…”

“…The same was found in a previous study on paddy rice [10] with the only exception of Fusarium spp. that seemed to decrease in over ripening in accordance with the total fungi trend; probably, different meteorological conditions registered after full ripening, in particular the almost total absence of rain observed in the area in year 2018, could have influenced Fusarium spp.…”

“…fungi, while STC was highest at full ripening and significantly decreased in over-ripening, as happened to the presence of A. versicolor (Table 1). A similar result for STC was found in a previous research, even if this decrease was not so intensive [10]. This could be due to environmental and substrate conditions that probably reduce fungal ability to produce STC while they have no effect on DON production.…”

“…for ochratoxin A (OTA) and citrinin (CIT) [9]. Recently, sterigmatocystin (STC) produced by Aspergillus versicolor was also found in rice and resulted the most common mycotoxin in Italian rice [10]. The European Commission fixed strict limits for mycotoxins in cereals; in particular, for rice destined for human consumption limits are present for AFs (2.0 µg/kg), OTA (3.0 µg/kg), and DON (750 µg/kg), making mycotoxin containment very important for product exchanges (EU Regulation 165/2010; EC Regulation 1881/2006; EU Regulation 1006/2015).…”