JOIMALOFAGRICDLTIJRALESEARCH 



DEPARTMENT OF AGRICULTURE. 



Vol. IV Washington, D. C, April 15, 1915 No. i 



PHOMA DESTRUCTIVA, THE CAUSE OF A FRUIT ROT 



OF THE TOMATO 



By Clara O. Jamieson, 

 Scientific Assistant, Cotton- and Truck-Disease and Sugar-Plant Investigations, 

 Bureau of Plant Indttstry 



OCCURRENCE AND GENERAL APPEARANCE OF THE DISEASE 



In March, 191 2, specimens of tomatoes (Lycopersicon esculentum) 

 affected with a fruit rot were sent in for examination from Cutler, Fla. 

 Mr. James B. Brown, who selected and sent in the specimens, stated in 

 an accompanying letter that great loss had been caused among the 

 farmers of Dade County, Fla., by this fruit-spotting. When received, 

 some of the fruit was green, some ripe, and some just beginning to color. 

 Most of the tomatoes had conspicuous dark spots on the side and at 

 the stem end. These spots, occurring on both green and ripe fruit and 

 measuring i to 3 cm. in diameter, were brownish black in color, with 

 definite outlines, while on the surface of the largest spots tiny dark 

 pustules could be seen. The firm, discolored tissue of the spots was 

 somewhat sunken, forming slight depressions, the surface of which was 

 membranous or crustlike, according to the stage of development. On 

 the ripe fruit the dark tissue was surrounded by a more or less watery- 

 looking zone. Plate A, figure i, shows the fruit-spotting as it appeared 

 upon one of the Cutler specimens. 



A microscopic examination of tissue cut from diseased areas occurring 

 on both green and ripe tomatoes showed a dense network of fungous 

 mycelium within the cells. The hyphae were septate, branched, and 

 hyaline to brown in color, while scattered over the surface of the myce- 

 lial growth numerous small dark pycnidia could be seen (PI. I, fig. i). 

 These pycnidia, varying considerably in size, were for the most part 

 round in outline, with a distinct central pore, out of which issued masses 

 of hyaline i -celled spores in long coils. The structure of a pycnidium 

 with its relation to the host cells is shown in Plate I, figure i, and a few 

 single hyphal strands in Plate I, figure 2. Bacteria were also numerous 

 in the tissue of the diseased area, and in some of the spots spores of 



Journal of Agricultural Research, Vol. IV, No. i 



Dept. of Agriculture, Washington. D. C. Apr. is, 191s 



G— 42 



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