UNITED STATES DEPARTMENT OF AGRICULTURE 



% BULLETIN No. 623 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



July 22, 1918 



CITRUS-FRUIT IMPROVEMENT: A STUDY OF BUD 

 VARIATION IN THE WASHINGTON NAVEL ORANGE 



By A. D. Shamel, Physiologist in Charge, L. B. Scott, Pomologist, and C. S. Pomeroy, 

 Assistant Pomologist, Fruit-Improvement Investigations, Office of Horticultural and 

 Pomological Investigations. 



CONTENTS. 



Introduction 1 



History of the Washington Navel variety — 2 



Variability within the variety 3 



Occurrence and frequency of bud variations. 5 



Objects of the investigations 7 



Plan of the investigations 7 



Methods of keeping performance records 9 



Descriptions of some of the important strains . 14 



Individual fruit variations 24 



Minor variations of fruits 27 



Lessons taught by these investigations 27 



Presentation of data 29 



Comparative value of the strains 140 



The unintentional propagation of undesirable 



strains 141 



The isolation of strains through bud selection. 142 



Top-working undesirable trees 144 



Summary 145 



INTRODUCTION. 



The Washington Navel orange is the most important citrus variety 

 grown in California. The total orange crop of the State, based upon 

 the shipments of a normal year, is about 39,500 carloads, of which 

 approximately 27,000 cars are of the Washington Navel variety. 1 

 In the report of the general manager of the California Fruit Growers' 

 Exchange for the year ended August 31, 1916, it is stated that a 

 total of 37,229 cars of oranges and grapefruit was shipped from 

 California during that period. The grapefruit crop amounted to 

 about 300 cars. It is also stated in this report that the California 

 Valencia orange crop of the year under discussion would amount 

 to between 13,000 and 14,000 carloads. No mention is made of the 

 size of the crops of the Mission Sweet Seedling, Mediterranean Sweet, 

 St. Michaels, Bloods, and other varieties, which are now grown to 

 only a very limited extent in California, probably not to exceed 1,500 



1 Wallschlaeger, F. O. The world's production and commerce in citrus fruits and their by-products. 

 Citrus Prot. League, Cal., Bui. 11, p. 70. 1914. 

 14575°— 17— Bull. 623 1 



