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Regeneration of Virus-Free Plants From Dark-Green Islands of Tobacco Mosaic Virus-Infected Tobacco Leaves. Harry H. Murakishi, Professor, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; Peter S. Carlson, Professor, Department of Crop and Soil Sciences, Michigan State University, East Lansing 48824. Phytopathology 66:931-932. Accepted for publication 15 December 1975. DOI: 10.1094/Phyto-66-931.

About 50% of plantlets regenerated from dark-green islands of tobacco leaves systemically infected with tobacco mosaic virus were virus-free. An obvious advantage of using these virus-free areas is that they are visually distinguishable and can be rapidly excised and plated to initiate regeneration. Leaf sap from such virus-free plantlets apparently contains a factor which is inhibitory to TMV infection. Our findings lend support to the hypothesis of Atkinson and Matthews that green islands are delimited by an as yet unidentified diffusible agent.