WHITE BURLEY TOBACCO RESISTANT TO ROOT-ROT. 7 



in some northern districts tobacco lias been given a definite and per- 

 manent place in rotation with other farm crops. 



DEVELOPMENT OF BURLEY STRAINS RESISTANT TO ROOT-ROT. 



Although a high measure of control of the root-rot in the Burley 

 section is attained by the system of rotation in use it is evident 

 that, on account of the extreme susceptibility of the Burley variety, 

 considerable disease occurs annually. The susceptibility of this 

 variety not only prevents continued culture when desired, but also 

 makes the growing of second and third crops on the soil quite a 

 game of chance. A type of Burley as resistant as some of the cigar 

 varieties and still possessing the yield and quality of the ordinary 

 Burley strains therefore would be extremely valuable in reducing 

 the annual loss from disease. Two possible means of producing such 

 a type are selection for disease resistance among commercial varie- 

 ties now grown and crossing resistant green types, such as some of 

 the cigar tobaccos, with White Burley, for the purpose of adding 

 disease resistance to the White Burley characteristics. The first 

 method, that is, selection for resistant strains in diseased fields, has 

 been resorted to in obtaining the results presented here. All tobacco 

 growers have seen fields in which the crop has made a very uneven 

 growth, though all the plants apparently had an equal chance to 

 start and develop. It sometimes happens that these fields behave in 

 this manner because of the presence of the root-rot and the use of 

 impure seed. Those plants which grow rapidly and stand out dis- 

 tinctly from their neighbors may be resistant to the disease. A 

 large number of these have been selected and the seeds saved from 

 the individual plants and grown in separate rows on sick soils the 

 following } T ear. A few of these selections have shown very distinct 

 resistance when compared with ordinary Burley, and these strains 

 propagated and tested over a period of several years under many 

 varied conditions have continued to maintain their original- degree 

 of resistance. In some cases these strains have been tested on a 

 rather large scale on both healthy and sick soils for the purpose of 

 comparing the quality of the cured leaf produced with that of the 

 ordinary White Burley. The results on the whole have been very 

 encouraging, although the ideal in mind has not yet been reached. 

 The resistant strains thus far produced and given commercial trial 

 are all of the drooping-leaf type and not stand-up Burleys, which 

 many growers prefer. Encouraging results have now been secured 

 in developing resistance in the stand-up types also, and it is expected 

 that these strains will soon be ready for testing commercially. 



A more important feature, however, is the quality of the resistant 

 Burleys obtained, as compared with the best strains of ordinary 



