Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 31, 2001
Publication Date: N/A
Interpretive Summary: Aflatoxins are poisonous chemicals produced by certain fungi. Aflatoxins can contaminate crops and cause them to lose value. We asked if there are reservoirs of aflatoxin-producing fungi in natural areas that might move into agricultural areas and cause aflatoxin contamination. Our study determined that both pods and debris from many desert trees harbor aflatoxin-producing fungi. We also found tree pods contaminated with aflatoxins. This is the first time aflatoxins have been reported in pods of desert trees. Desert animals frequently eat the pods and there is possible exposure of desert fauna to aflatoxins. Our results suggest that any use of pods from these trees should take into consideration possible aflatoxin contamination. The study also indicates that aflatoxin-producing fungi may move from native areas to agricultural fields.
Technical Abstract: Aspergillus section Flavi was frequently associated with desert tree legumes in uncultivated areas of the Sonoran desert. Eighty-seven percent of 270 samples of debris and fruits of mesquite, ironwood, acacia, and palo verde were positive for Aspergillus section Flavi, with two species present: A. flavus (S and L strains) and A. tamarii. Aspergillus flavus was the most common member of section Flavi with an incidence of 87 among 3763 isolates examined. Quantities of A. flavus were highest on mesquite pods with an average of 2.3 x 10**6 CFU/g. In vitro, most desert legumes allow significant growth, reproduction, and aflatoxin production by A. flavus, with mesquite pods supporting production of 1 x 10**10 propagules/g and 5,000 ug/kg of aflatoxin B1. Twenty percent of legume pods collected in the desert contained measurable quantities of aflatoxin ranging from 1 to >2500 ug/kg. The highest incidence (33%) and average aflatoxin accumulation (891 ug/Kg) was found on mesquite pods. Insect damaged mesquite pods had significantly higher aflatoxin than undamaged pods. Legume debris may be an important reservoir of aflatoxin-producing fungi and pods a significant source of aflatoxin exposure in native Sonoran desert habitats.