The Influence of Citrinin on TMV Infection

Citrinin isolated from cultures of Penicillium sp. AK-019 had a markedly inhibitory effect on local lesion formation on Nicotiana glutinosa leaves caused by tobacco mosaic virus (TMV). This paper reports the influence of this antibiotic on TMV infection. (1) When 100μg/ml of citrinin were infiltrated into N. glutinosa leaves through the petioles or by placing the lower surfaces of detached leaves on the solution, local lesion formation was almost completely inhibited. Even though by dipping the inoculated leaves into the solution for a few minutes, a considerable inhibitory effect on lesion formation was observed. On the other hand, citrinin did not affect TMV infection when TMV and citrinin were mixed in vitro and inoculated on N. glutinosa leaves. (2) Although local lesions were not formed on N. glutinosa leaves by the treatment with citrinin of 100μg/ml, infectious TMV apparently multiplied in the leaves and the TMV concentration gradually decreased with the prolonged times of treatment. In the case of citrinin concentration below 10μg/ml, however, TMV multiplied at the same rate as did in nontreatment. (3) The effect of citrinin, which inhibits or delays the local lesion production by TMV on N. glutinosa leaves, is presumably caused by the delay of the rate of TMV multiplication in the leaves. It is suggested that this antibiotic acts simply on the surface of inoculated leaves.