VARIETAL DIFFERENCES IN ACCUMULATION OF OCHRATOXIN-A IN BARLEY AND WHEAT CULTIVARS AFTER INOCULATION OF PENICILLIUM-VERRUCOSUM

The natural content of ochratoxin A in grain samples of 6 barley, 2 br ead wheat and 1 durum wheat cultivars varied from <0.1 to 0.4 ng/g gra in. Samples of the analysed cultivars were surface sterilized and kept in humidity chambers at 20 degrees C and water activity (a(w)) 0.75 o r a(w) 0.85 for 8 days. For both environments, the resulting grain equ ilibrium water content varied between cultivars of both barley and whe at, attributable to agronomic traits. The samples were then inoculated with Penicillium verrucosum and incubated for up to 23 weeks. With ti me, all cultivars had increasing ochratoxin A content, with maximum co ntent in different barley cultivars ranging from 34 to 630 ng/g grain for a(w) 0.75, and 39 to 260 000 ng/g for a(w) 0.85. Corresponding val ues for the wheat cultivars were 25 to 2 300 ng/g and 650 to 5 200 ng/ g. Significant varietal differences in ochratoxin A accumulation were observed for barley (P < 0.0001), attributable to equilibrium water co ntent, amylose content and natural ochratoxin A; and for wheat (P < 0. 0001), attributable to protein content and natural ochratoxin A. Barle y 'SW 1306 95/1203' and 'SW 906129 Waxy', and wheat 'SW 39103' accumul ated significantly less ochratoxin A than the other cultivars.