JOURNAL OF AGRICDLTIJRAL RESEARCH 
Vol. XIV Washington, D. C., August 26, 1918 No. 9 
SUSCEPTIBILITY AND RESISTANCE TO CITRUS- 
CANKER OF THE WILD RELATIVES, CITRUS FRUITS, 
AND HYBRIDS OF THE GENUS CITRUS 1 
[PRELIMINARY PAPER] 
By George L. Peltier 2 
Plant Pathologist , Alabama Agricultural Experiment Station * 
COOPERATIVE INVESTIGATIONS BETWEEN THE OFFICE OF CROP PHYSIOLOGY AND 
BREEDING INVESTIGATIONS, BUREAU OF PLANT INDUSTRY, UNITED STATES 
DEPARTMENT OF AGRICULTURE, AND THE DEPARTMENT OF PLANT PATHOLOGY, 
ALABAMA AGRICULTURAL EXPERIMENT STATION 
INTRODUCTION 
While many observations (see Table I) have been made on the suscep¬ 
tibility and resistance to Citrus-canker (caused by Pseudomonas ciiri 
Hasse) of the more common commercial varieties and species of Citrus, \ 
no systematic comparison has, as yet, been attempted to determine the 
susceptibility and resistance to canker of the wild relatives, the more 
obscure species and varieties, and the hybrids of Citrus as a whole. 
Owing to the strict quarantine measures against Citrus-canker and the 
inability to get together a representative collection of plants because 
of the time and funds necessary, a comparison of this kind has been , 
impossible. Fortunately, through the efforts of Mr. W. T. Swingle, we 
now have represented in this country one of the most complete collec¬ 
tions of Citrus plants and their relatives to be found in the world. 
Through the cooperation of Mr. Swingle, the writer has been able to 
obtain plants from this collection, representing a large part of the family 
Rutaceae, to which the genus Citrus belongs. Plants have been placed 
for this study in the greenhouses at Auburn, Ala., and in the isolation 
field in the vicinity of Loxley, Ala. 
1 Published with the approval of the Director of the Alabama Agricultural Experiment Station. 
2 The writer gratefully acknowledges his indebtedness to the following personnel of the Bureau of Plant 
Industry: Dr. K. F. KeUerman, Associate Chief, and Mr. W. T. Swingle, Physiologist in Charge, Crop 
Physiology and Breeding Investigations, for their cooperation and many helpful suggestions; Mr. D. C. 
Neal, Pathologist, for assistance rendered during the progress of the work; Mr. T. Ralph Robinson, 
Physiologist, Office of Crop Physiology, for his aid in the preparation of the manuscript; and Miss Wead, 
of the same office, for the preparation of the table and bibliography. 
Journal of Agricultural Research, 
Washington, D. C. 
oy 
(337) 
Vol. XIV, No. 9 
August 26, 1918 
Key No. Ala.-4 
