Turnip mosaic ^ 



By Max W. Gardner, Associate in Botany, and James B. Kendrick, Assistant in 

 Botany, Purdue University Agricultural Experiment Station 



In one comer of a small field of turnips near South Bend, Ind., Octo- 

 ber 12, 1920, a considerable percentage of the plants were found affected 

 with an unmistakable mosaic disease. The symptoms were typical of 

 mosaic diseases in general. The leaves were stunted, misshapen, and a 

 lighter green with dark green blisters or puffy areas. Many of the leaves 

 were extremely distorted by crinkling and folding (PI. 20, A). The dis- 

 ease seemed to be confined to one area in the field, to some extent coin- 

 cident with a heavy infestation of tarnished plant bugs. 



Several diseased plants were transplanted to pots in the greenhouse, 

 where they continued to form new leaves during the winter. The mosaic 

 symptoms exhibited by the new foliage formed under greenhouse con- 

 ditions were not quite so extreme as had been noted in the field. One 

 of these plants, with mottled and spindling leaves, is shown in Plate 20, 

 B, as it appeared in December. 



Inoculation of a number of potted turnip and radish seedlings was made 

 by breaking off a leaf and rubbing the wound with crushed leaf tissue 

 from one of the mosaic plants. Out of 21 turnip seedlings inoculated 

 early in January, 13 developed characteristic mosaic symptoms. The 

 first symptoms were noted 26 days after inoculation. The turnips inocu- 

 lated showed some varietal difference from the plants collected in the 

 field in that the leaves were much less distinctly pinnatifid. Out of 46 

 radish seedlings, including both white and red varieties, similarly inocu- 

 lated, none developed mosaic symptoms. 



A later series of inoculations was made January 26 by wounding the 

 plants with a needle and rubbing the wounded areas with a piece of cotton 

 soaked in the juice from mosaic leaves ground up in a mortar. Ten out 

 of 14 turnip plants thus inoculated developed the mosaic disease. The 

 first symptoms were noted 16 days after inoculation. No mosaic devel- 

 oped among 13 control plants similarly treated except that sterile water 

 was substituted for the mosaic virus. Twenty-two radish plants were 

 also inoculated, and none of these developed the disease. Subsequent 

 reinoculation of turnip plants from one of these radish plants produced 

 no mosaic. The mosaic disease of turnips is therefore readily transmis- 

 sible to turnips but not to radishes. 



' Contribution from the Botanical Department of Purdue University Agricultural Experiment Station, 

 I,aFayette, Ind. 



After this article was prepared it was learned that Eugene vS. Schultz, of the Bureau of Plant Industry, 

 United States Department of Agriculture, was also working on this disease. 



Journal of Agricultural Research, Vol. XXII, No. 3 



Washington, D. C. Oct. 15, 1921 



zw Key No. Ind.- 1 1 



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