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Pomona College Journal op Economic Botany. 



INOCULATION EXPERIMENTS 



These experiments were carried on in order to determine the parasitic 

 nature of the different strains of Fusarium studied; and to determine if 

 strains isolated from the carnation were capable of producing disease in the 

 potato, and vice versa to determine if potato strains were capable of pro- 

 ducing disease in the carnation. The plants used in the experiments were 

 kept in one of the University of California greenhouses, and unless other- 

 wise stated, they were given ordinary treatinent. Two methods of inocula- 

 tion have been tried. The first consisted in simply burying pure cultures 

 of the strain under investigation in the soil, and in contact with the stem 

 of the plant. The second consisted in making a narrow .slit, with a sterile 

 knife, in the stem of the plant, even with the surface of the ground, plac- 

 ing the spores and mycelium of a pure culture in it, and sealing the wound 

 with paraffin. The details of each experiment follow: — 



February 5th — Two Prosperity carnation plants, about six weeks old, 

 were inoculated by the first method. One j)]ant was inoculated with a pure 

 culture of strain (IV) and the other with a pure culture of .strain (VII). 

 Neither plant became infected with the disease. Two other i)lants of the 

 same variety were kept under .similar conditions for control. 



February 21st — Two Encliantress carnation plants, twelve weeks old, 

 were inoculated with strains (IV) and (VII), respectively, by means of the 

 "slit" method. In eleven days the plant inoculated with strain (IV) wilted, 

 its foliage had a yellowish cast, and its .stem was affected with the disease. 

 An examination of the stem beneath the paraffin revealed the presence of 

 freshly developed spores and mycelium. The plant inoculated with strain 

 (VII) remained normal. Two plants of the same variety were used for 

 control and given the same treatment, except that their stems were not 

 cut and sealed with paraffin. 



February 21st — Three carnation plants of the Estelle variety, about 

 one year of age, were inoculated with pure cultures of strains (IV), (VII), 

 and (H), respectively, by the "slit" method. These inoculations were not 

 successful. 



March 7th — An Enchantress carnation, about one year of age, was inocu- 

 lated with a pure culture of strain (R) by the "slit" method. The prog- 

 ress of the disease in this plant was slow, and no signs of injury were 

 noticed until April 5th, then the lower branches became yellowish and one 

 side of the stem was affected with a dry rot. On April 15th the plant, 

 although it was not dead, was removed from its pot and a microscopical 

 examination made of the diseased tissues of the stem. One-half of the 

 stem was decayed at the point of infection, and, with the exception of a 

 slender brown streak, consisting of broken-down parenchyma tis.sue, the 

 decay extended only about one and one-fourth inches above and below 

 this point. An abundance of mycelium could be observed in cross sections 

 of the decayed and partially-decayed areas. Segments of the affected stem 



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