UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 62 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



July 25, 1918 



CITRUS-FRUIT IMPROVEMENT: A STUDY OF BUD 

 VARIATION IN THE VALENCIA ORANGE. 1 



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

 Pomeroy, Assistant Pomologist, Fruit- Improvement Investigations, Office of Hor- 

 ticultural and Pomological Investigations. 



CONTENTS. 



California citrus varieties 1 



History of the Valencia variety 2 



Variability within the variety 3 



Occurrence and frequency of bud variations . 4 



Objects of the investigations 5 



Plan of the investigations 6 



Methods of keeping performance records 7 



Descriptions of some of the important strains 8 



Individual variations of fruits 12 



Minor variations of fruits 13 



Lessons taught by these investigations 13 



Presentation of data 14 



Comparative value of the strains 114 



The unintentional propagation of undesirable 



strains 115 



The isolation of strains through bud selection 116 



Top-working undesirable trees 118 



Summary 119 



CALIFORNIA CITRUS VARIETIES. 



The commercially important varieties of citrus fruits grown in 

 California are the Washington Navel 7 the Valencia, and the Mediter- 

 ranean (Mediterranean Sweet) oranges; the Dancy tangerine; the 

 Eureka and Lisbon lemons; and the Marsh (Marsh Seedless) grape- 

 fruit. Other less important varieties grown only to a limited extent 

 include the St. Michael, Navelencia, Ruby blood, and Malta blood 

 oranges, and the Villafranca lemon. Of the two leading orange 

 varieties the Washington Navel is by far the most widely cultivated, 

 producing an annual crop of about 27,000 carloads of fruit. 2 This 

 variety ripens its fruit from November to June, inclusive. The 

 Valencia ripens its fruit from June to October, inclusive, and produces 



1 This is the second in a series of publications summarizing the citrus-fruit improvement investigations of 

 the Department of Agriculture. The first report of this character was presented in the following publica- 

 tion: Shamel, A. D., Scott, L. B., and Pomeroy, C S. Citrus-fruit improvement: A study of bud varia- 

 tion in the Washington Navel orange. U. S. Dept. Agr. Bui. 623, 146 p., 16 figs., 19 pi. 1918. In that 

 bulletin the methods of conducting the investigational work are described more in detail than in the pres- 

 ent publication. 



2 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. 



14648°— 18— Bull. 624 1 



