Frenching Symptoms Produced in Nicotiana Tabacum and Nicotiana Rustica with Optical Isomers of Isoleucine and Leucine and with Bacillus Cereus Toxin

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Abstract
N. tabacum (Maryland Medium Broadleaf and Havana 142) and N. rustica (Mahorka 1) were grown aseptically on mineral agar under about 500 fc. of white fluorescent light. Addition of either L-isoleucine or L-alloisoleucine produced symptoms of frenching in both spp. L-Leucine was also effective with N. rustica. Relative effectiveness on tobacco was alloisoleucine > isoleucine; on N. rustica, alloisoleucine > leucine > isoleucine. L-Alloisoleucine was 4 times more effective (minimal range 2 to 8 ppm.) than L. isoleucine with tobacco. D-Isoleucine, D-leucine, and D-alloisoleucine did not cause frenching symptoms. Neither did glycyl-L-leucine nor L-leucyl-glycine. A heat stable toxin from B. cereus also caused production of frenching symptoms in tobacco.