Interacting Abiotic Factors Affect Growth and Mycotoxin Production Profiles of Alternaria Section Alternaria Strains on Chickpea-Based Media

Chickpea is susceptible to fungal infection and mycotoxin contamination. Argentina exports most of its chickpea production; thus, its quality is of concern. The Alternaria fungal genus was found to be prevalent in chickpea samples from Argentina. The species within this genus are able to produce mycotoxins, such as alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TA). In this context, we evaluated the effect of water activity (0.99, 0.98, 0.96, 0.95, 0.94, 0.92, and 0.90 a(W)), temperature (4, 15, 25, and 30 degrees C), incubation time (7, 14, 21, and 28 days), and their interactions on mycelial growth and AOH, AME, and TA production on chickpea-based medium by two A. alternata strains and one A. arborescens strain isolated from chickpea in Argentina. Maximum growth rates were obtained at the highest a(W) (0.99) and 25 degrees C, with growth decreasing as the a(W) of the medium and the temperature were reduced. A. arborescens grew significantly faster than A. alternata. Mycotoxin production was affected by both variables (a(W) and temperature), and the pattern obtained was dependent on the strains/species evaluated. In general, both A. alternata strains produced maximum amounts of AOH and AME at 30 degrees C and 0.99-0.98 a(W), while for TA production, both strains behaved completely differently (maximum levels at 25 degrees C and 0.96 a(W) for one strain and 30 degrees C and 0.98 a(W) for the other). A. arborescens produced maximum amounts of the three toxins at 25 degrees C and 0.98 a(W). Temperature and a(W) conditions for mycotoxin production were slightly narrower than those for growth. Temperature and a(W) conditions assayed are those found during chickpea grain development in the field, and also could be present during storage. This study provides useful data on the conditions representing a risk for contamination of chickpea by Alternaria toxins.