Mycotoxin production by Fusarium proliferatum isolates from rice with Fusarium sheath rot disease

Twenty samples of unpolished (rough) rice collected in Arkansas and Texas during the 1995 harvesting season from fields exhibiting Fusarium sheath rot disease or panicle blight were previously shown to include 8 samples positive for fumonisin B₁ (FB₁) in the range 2.2-5.2 ppm, and moniliformin (MON), but no beauvericin (BEA), deoxynivalenol, its derivatives or zearalenone were detected. Fifteen cultures of F. proliferatum were established from the 20 rough rice samples. Single spore isolates of each culture were grown on rice and tested for the production of fumonisins (FB₁, FB₂, FB₃, etc.), MON and BEA. All 15 isolates produced FB₁, FB₂, MON and BEA in culture on rice. No deoxynivalenol, its derivatives or zearalenone were detected. Seven cultures produced FB1 at >50 ppm (range 80-230 ppm), with the rest producing FB₁ in the range 14-43 ppm. FB₂ was produced in the range 5-47 ppm, and those cultures which produced the most FB₁ also produced the most FB₂. Of the 15 cultures producing MON, 11 produced it at > 100 ppm in the range 188-6018 ppm, with the rest producing in the range 7-64 ppm. BEA was produced in the range 109-1350 ppm. Other derivatives of fumonisins, including FA₁, FA₂ and partially hydrolyzed FB₁, as well as several unknown metabolites including a compound with MW 414, were identified in culture extracts by continuous flow fast atom bombardment with ion spray mass spectrometry (CF/FAB/MS). Further study is needed to identify the factors that control production of FB₁, MON and BEA by F. proliferatum in culture and in field samples.