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Effect of Detached Leaf Treatment on Tobacco Mosaic Virus Multiplication in Tobacco and Bean Leaves. Yoichi Nakagaki, Plant Pathology Laboratory, Faculty of Agriculture, Nagoya University, Chikusa-ku, Nagoya 464-00, Japan, Present address of senior author: Plant Pathology Laboratory, Faculty of Agriculture, Kinki University, Higashi Osaka, Osaka 577-00; Tokuzo Hirai, Plant Pathology Laboratory, Faculty of Agriculture, Nagoya University, Chikusa-ku, Nagoya 464-00, Japan. Phytopathology 61:22-27. Accepted for publication 15 July 1970. DOI: 10.1094/Phyto-61-22.

Effect of host senescence on tobacco mosaic virus (TMV) multiplication and local lesion formation was investigated by using attached and detached tobacco and bean leaves. In the systemic host, detachment of leaves before inoculation caused remarkable decrease in the amount of nucleic acids and dry weight, but not in chlorophyll and soluble protein per day weight. In leaves detached for 2 days, however, TMV concentration increased 42% over attached leaves, but after longer periods virus concentration was lower than in attached leaves. Detachment of leaves after inoculation promoted chlorophyll degradation, whereas TMV infectivity was slightly increased over that in attached leaves until 4 days after inoculation. TMV concentration was found similar in both the detached and attached leaves 5-6 days after inoculation, despite the fact that chlorophyll content was sharply lowered. In bean leaves, detachment of leaves just after inoculation decreased the number of local lesions by 33%; whereas, diameter of lesion size and TMV infectivity within the lesions increased about 2.3 and 4.3 times over that shown by attached leaves, respectively. It is suggested that moderate leaf senescence associated with partial degradation of nucleic acids and protein closely relates with increases in TMV concentration in tobacco and bean leaves.