BROWN ROT OF SOLANACEAE. 



Synonyms: Tomato-wilt, Potato-rot, Blight of Egg-plant, Pepper-blight, Granville 

 Wilt of Tobacco, etc. 



DEFINITION. 



This is a specific communicable disease of potatoes, tomatoes, egg-plants, etc., char- 

 acterized by a sudden wilting and shriveling of the foliage, with drooping of the softer shoots 

 and a brown stain in the vascular bundles, which are filled with a great number of bacteria. 

 It also causes more or less disorganization of the parenchyma, especially of the pith. Young 

 watery plants are much more subject to general infection than old and woody ones. The 

 internal browning is frequently visible on the surface of stems, etc., as dusky patches or 

 streaks. In woody plants the leaves may become yellow and die without wilting. In 

 potato tubers it rots the region of the vascular ring with a brown stain (pi. 23, figs. 8, 10). 



HOST-PLANTS. 



This disease has been observed in the United States in potatoes (Solanum tuberosum), 

 a wild plant obtained from Montevideo, Uraguay, and supposed to be Solanum commersoni 

 (pi. 24, fig. 2), egg-plant (5. melongena), tomato (5. lycopersicum) , and in tobacco. Hunger 

 has reported its occurrence on tomatoes, tobacco, and peppers in the Dutch East Indies and 

 Honing in a variety of non-solanaceous plants see History and also a separate chapter on 

 Tobacco-wilts (p. 220) and on a disease of peanuts (p. 151). The disease has been successfully 

 inoculated by the writer into potatoes and tomatoes many times over, and also into the 

 following: Nicotiana tabacum (recent experiments), Solanum nigrum, Datura stramonium, 

 D. metelloidcs, Physalis crassi/olia, P. philadelphica, and Petunia sp. (hybrid). 



In heliotrope, Ricinus communis, Vigna catjang, and Portulacca oleraceae, the organism 

 lived for some weeks in the inoculated area, but no general disease of the plant was devel- 

 oped. Inoculations into the following plants were unsuccessful: Cucurbita foetidissima, 

 Cucumis sativus (stem and fruit*), Nicotiana tabacum (1895, 1896, 1901, 1905}), Capsicum 

 annum, Solanum muricatum, S. carolinense, S. dulcamara, Pyrus communis, Eleusine indica, 

 Abutilon avicennae, and Pelargonium zonale. 



Beyond one unsuccessful trial no attempts have been made to inoculate it into egg- 

 plants, because none happened to be at hand when the writer was making his experiments, 

 but he obtained numerous infections on tomato and potato with bacteria taken from the 

 egg-plant, and Rolfs has inoculated into the latter very successfully. Inoculations into the 

 stems of cucumber plants caused no general sickening, but in some cases (not all) there was 

 a local enlargement of the inoculated part. The surfaces of these stems were not, however, 

 sterilized before inoculation (by needle-puncture), and only two cases of this kind occurred. 

 Local enlargements have been very frequent on tomato stems inoculated with old isolations 

 and feebly virulent strains. Inoculations in the summer of 1 903 showed Datura metelloides 

 (vol. I, fig. 4) to be very susceptible. Datura fastuosa and D. cornucopiae were stunted, but 

 managed to overcome the disease. A specimen of Datura tatula inoculated in 1896 resisted 

 a virulent strain of the organism, i. e., one that destroyed D. stramonium and other plants. 



'Inoculations in 1896 into full-grown, green cucumber fruits removed from the parent plant and placed under bell- 

 jars led in several cases to a soft watery rot involving the whole interior of the fruit and similar to that sometimes 

 observed in the field in ripening cucumbers. Inasmuch, however, as plate-cultures were not made from the bacteria 

 swarming in the interior of these fruits, the possibility of this phenomenon being due to other bacterial organisms was 

 noted at the time as not excluded. This experiment was repeated in the summer of 1 901 on six ripe and ripening cucum- 

 bers, in the open air, attached to the vine, with entirely negative results. Each fruit was inoculated copiously by means 

 of a dozen or more deep needle-punctures. The check-plants, consisting of the growing shoots of tomatoes and pota- 

 toes, contracted the disease promptly, but the cucumbers showed no signs. 



fFor later successful inoculations, see Wilt-Diseases of Tobacco. 



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