TOBACCO MUTATIONS 



Sports of Great Value Apparently Not Due to Hybridization But to Some Change 

 in the Reproductive Cells After Fertilization — History of 



the Mutants.' 



H. K. Hayes 

 Associate Professor of Plant Breeding, College of Agriculture, University of Minne- 

 sota, St. Paul, Minn. 



SOME one has said that inheritance 

 is the ability to produce certain 

 characters under certain favor- 

 able conditions of environment. 

 As some plants have slightly more 

 favorable conditions than others, even 

 when all are grown under fairly uniform 

 environment, we find that there are 

 always some plants in which the char- 

 acter under observation is more fully 

 developed than in others. Permanent 

 improvement in plants by the selection 

 of these fluctuations has not, however, 

 generally been obtained, and when this 

 method has given new types the results 

 can, as a rule, be more logically ex- 

 plained as due to the isolation of the 

 better biotypes of the race than by the 

 gradual production of a new character 

 by continuous selection. The ability of 

 a breeder to produce new types is there- 

 fore dependent on the possibility^ of ob- 

 taining new inheritable variations. 



We now know that variation can be 

 produced by crossing. If we cross two 

 biotypes which differ by certain char- 

 acters, an increase in variability is ob- 

 tained in the second generation after 

 the cross. The selection in this genera- 

 tion of those plants which most nearly 

 approach the desired habit, and further 

 pedigreed breeding until the races breed 

 true for the desired characters, have 

 produced many new plant varieties of 

 economic importance. 



New types in supposedly homozygous 

 material, which suddenly appear and 

 cannot be explained by crossing, are 

 known as mutations. It is the purpose 

 of this paper to describe a constantly 

 recurring mutation in Connecticut Ha- 



vana tobacco and to give further notes 

 in regard to the sport which appeared 

 in 1912 in a field of Connecticut Cuban 

 shade tobacco. 



SHADE TOBACCO IN CONNECTICUT. 



The history of the production of the 

 Connecticut Cuban shade type is well 

 known. It was first grown in this 

 country in 1904 from seed which was 

 brought from Cuba the previous year 

 by William Hazel wood, of New York 

 City. The first few crops were variable 

 in habit, but selection soon served to 

 isolate numerous biotypes. One line 

 known as 13-29 proved' its superiority. 

 Seed from a number of self-fertilized 

 plants of this line was saved in 1908 and 

 was used for planting in 1910 at the 

 Windsor Tobacco Growers' Corporation 

 in Bloomfield, giving a crop of uniform 

 appearance in which no variations of 

 importance were noticed. A large 

 nrunber of seed plants of this crop were 

 saved, although the individual seed- 

 heads were not separately covered 

 with a manila paper bag to prevent 

 crossing, as was the plan from 1904 to 

 1909. It does not seem very likely, 

 however, that much crossing would 

 take place under the cheesecloth cover, 

 and even if some crossing took place 

 it would be between homozygous indi- 

 viduals. Thus, prior to 1910 the Cuban 

 variety was selfed for six generations and 

 gave every evidence that it was of a 

 homozygous nature. 



Further evidence that this Cuban 

 strain was homozygous for leaf number 

 may be given by the following experi- 

 ment. In 1910, 150 plants grown from 



1 This Study was made at the Connecticut Experiment Station in New Haven. 



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