UNITED STATES %i*"'™«t 



DEPARTMENT of AGRICtflL' 



DEPARTMENT CIRCULAR 264 



Washington, D. C. May, 1923 



FROST RESISTANCE IN FLAX. 



ROBERT L. DAVIS, 



Assistant Plant Breeder, OflBce of Fiber-Plant Investigations, Bureau of Plant Industry. 



Page. 



Introduction 1 



The temperature range for f rest tests 



with flax 2 



The external nature of. frost injury- 3 



CONTENTS. 



Page. 



Varietal differences in frost resist- 



aDoe 5 



Conclusions 7 



INTRODUCTION. 



A study of frost injury in flax is important to the breeder because 

 it is best to plant flax early in the spring, and at this time frost in- 

 jury is often quite severe. The early seeding of flax gives it a num- 

 ber of advantages. It can compete with weeds and disease organisms 

 more successfully and is less susceptible to injury from drought or 

 lodging. Flax will grow at a lower temperature than most weeds, 

 and early seeding gives it a head start so that it can shade out the 

 weeds. The high soil temperatures of July and August favor the 

 development of flax wilt and flax rust. The stems of late-seeded flax 

 are more succulent at this time than those of early-seeded flax, and 

 hence the former are more susceptible to the attack of fungi. Under 

 greenhouse conditions flax is not infected with flax wilt below 59° F., 

 although flax thrives well at 55° F. The optimum range of tem- 

 perature for the growth of Fusarium lini Bolley, the organism that 

 causes flax wilt, is 79° to 82° F., and it may be regarded as a high- 

 temperature organism.^ Early-seeded flax can take advantage of 

 the spring rains and make a steady growth during cool weather that 

 gives stiffness to the stems ; late-seeded flax may either be stunted by 

 drought or a very rapid growth induced by heavy rainstorms and 

 hot weather may render it liable to lodging. 



Field observations have given indications that there are varietal 

 differences in the ability of flax to resist frost. Flax may be in- 

 jured by cold weather immediately after seeding that interferes with 



1 Tisdale, W. H. The relation of temperature to the growth and infecting power of 

 Fusarium lini. In. Phytopathology, v. 7, p. 356-360, 1 fig., pi. 11. 1917. 



33347—23 



