Production of toxins by Alternaria alternata and A-radicina and their effects on germination of carrot seeds

A profile of toxin production by Alternaria alternata and A. radicina isolated from carrot seeds was determined. Ten isolates of each fungus were used for the study. All isolates of A. alternata produced alternariol (AOH), alternariol methyl ether (AME), altenuene (ALT) and tenuazonic acid (TeA), and eight produced altertoxin I (ATX I). The isolates varied in level of toxin production. The highest toxigenicity was observed for TeA. In isolates of A. radicina, only radicinin (RAD) was detected. As compared with single isolate cultures of A. alternata and A. radicina, a higher productivity of RAD and, in general, lower productivity of AOH, AME, ALT and TeA was observed in dual cultures of the above-mentioned fungi. Treatment with solutions of extracts containing Alternaria toxins resulted in a lower percentage of normal seedlings and increased the percentage of necrotic seedlings in most cases. TeA at high concentrations as well as the joint presence of RAD and TeA had the greatest negative effects on seed germination.