UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 1015 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



S L^^LTt, 



Washington, D. C. 



March 28, 1922 



DEVELOPMENT OF WILT-RESISTANT TOMATOES. 



By Feed J. Pritchaed, Physiologist, Office of Cotton, Truck, and Forage Crop 



Disease Investigations. 



CONTENTS. 



Prevalence and characteristics of 

 tomato wilt 



Development of resistant varieties 



Selection of material 



Preparation of the breeding 



plats 



Method of selection 



Varietal resistance 



Intravarietal variation 



Behavior of selections 



Page. 



Development of resistant varieties — 

 Continued. 



Behavior of resistant varieties- 9 



Effect of continuous selection 9 



Duration of resistance J. 10 



Results of field tests 11 



Origin and description of wilt-re- 

 sistant varieties 15 



Summary 17 



PREVALENCE AND CHARACTERISTICS OF TOMATO WILT. 



Tomato wilt {Fustwium lycopersici) causes an estimated annual 

 loss of more than 115,000 tons of tomatoes in the Middle Atlantic, 

 Gulf, and lower Mississippi Valley States. 1 As it is prevalent also in 

 the Ohio River Valley, in California, and in parts of Colorado and 

 Utah, it reduces the yield even more than is expressed by these fig- 

 ures. This loss can and should be overcome by the use of wilt-re- 

 sistance varieties. 



Wilt is characterized in its early stage by a wilting of the plant 

 and an upward and inward rolling of the leaves (PL I, fig. 1) . Later 

 the lower and finally the upper leaves turn yellow and slowly die. 

 When a branch is thus deprived of its foliage it dies back from the 

 tip, turns brown, and shrivels. Some of these final changes and the 

 varied progress of the disease in different branches are shown in 



1 The loss from wilt in the canning crop of tomatoes estimated by the Plant-Disease 

 Survey of the Bureau of Plant Industry from reports of State and Federal pathologists 

 for the year 1918 was 115„000 tons, but this did not cover the whole area infested by 

 wilt nor did it include the loss in the crop grown for trucking and home gardening. 

 68713° — 22 1 



