Mouse toxicty of fungi of tobacco.

A bioassay for fungal toxins based on the intraperitoneal injection of test materials into mice was used to screen 976 cultures isolated from tobacco and grown in a high-protein baby cereal and also to determine whether samples of tobacco damaged by fungi are more toxic than samples of apparently sound tobacco. Of 236 fungal isolates from noncured tobacco, 79% were lethal when homogenized cultures of these isolates were tested. Forty-nine per cent of 740 fungi isolated from cured tobacco were lethal.

Fungi Isolated from Flue-cured Tobacco at Time of Sale and After Storage.

The fungi isolated from 100 samples of flue-cured tobacco from 12 markets in 2 tobacco belts comprised 11 genera, including 10 species of Aspergillus. The mean percentage per sample isolated from 62 samples of tobacco from Middle Belt markets was Alternaria, 40.6%; Aspergillus niger, 47.

Fungi isolated from tobacco leaves and brown-spot lesions before and after flue-curing.

Discs of tissue excised from ripe nonflue-cured and flue-cured tobacco leaves, harvested on six dates and cultured on three selective media, yielded 21 and 24 genera of fungi, respectively. Of 5,094 fungi isolated from 3,240 pieces of nonfluecured leaf tissue, 89.5% comprised five genera, Alternaria, Cladosporium, Epicoccum, Trichoderma, and Nigrospora.

Fungi Isolated from Damaged Flue-cured Tobacco.

Species of Aspergillus were the most prevalent fungi isolated from 51 samples of damaged flue-cured tobacco of the 1966 U.S. crop, comprising 57% of the total isolates.