UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 1015 
^gp' Contribution from the Bureau of Plant Industry '^&3f\ >V» 
J&F^S&U WM. A. TAYLOR, Chief *y^?">W6v 
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. 
Page, 
Development of resistant varieties — 
Continued. 
Behavior of resistant varieties. 9 
Effect of continuous selection 9 
Duration of resistance. 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 (Fmcvrium 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 
