UNITED STATES DEPARTMENT OF AGRICULTURE 



DEPARTMENT BULLETIN No. 1195 



Washington, D. C. 



March, 1924 



STERILITIES OF WILD AND CULTIVATED POTATOES WITH REFERENCE TO 



BREEDING FROM SEED. 



By A. B. Stout, Director of Laboratories, New York Botanical Garden, and C. F. Clark , 

 Horticulturist, Office of Horticultural Investigations, Bureau of Plant Industry. 



Introduction 



<5eneral survey of the types of sterility in the 



potato 



Sterility due to nonfiowering 



Sterility from one-sided impotence, or 

 intersexualism 



CONTENTS. 



Page. I Page. 



1 i General survey, etc.— Continued. 

 i Sterility in hybrids 22 



2 Sterility from incompatibiUty 23 



2 1 Results of the steriUty survey 26 



t Summary 31 



4 ' Literatiu-e cited 31 



INTRODUCTION. 



The importance of the reproduction of the potato from seed balls 

 is shown by the fact that nearly all of the most valuable varieties 

 now in cultivation have been thus obtained. A few, however, are 

 claimed to have originated as bud sports, but these have played a 

 relatively unimportant part in potato production. Through seed 

 propagation there have been developed numerous varieties, differ- 

 ing in habit of growth, in time of maturity, in size, shape, and 

 quality of tubers, and in adaptability to conditions in different 

 localities. While there is still chance for further improvement 

 regarding these characteristics, the most immediate demand for 

 seed reproduction is in the need for varieties resistant to disease. 

 The rapid spread of diseases of the potato during recent years, par- 

 ticularly the extremely infectious diseases of the mosaic and leaf- 

 roll types that are transmitted by aphids, makes breeding for resist- 

 ance to disease highly desirable, if not necessary. 



The greatest difficulty encountered in the breeding of the potato 

 from seed is the marked sterility or lack of fruitfulness very generally 

 present. This has been experienced by all who have sought to 

 breed this plant. Many observations have been made with reference 

 to the various aspects of fruitlessness, and numerous views have been 

 expressed regarding the causes and conditions involved. No clear 

 outline of this situation with reference to the distinctions between 

 the several types of sterility now known to be present in other 



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