REPORT OF SOCIETY 



75 



racteristics or a very limited adaptability. Under such considions, it becomes 

 necessary for the plant breeder to make use of hybridization with other types 

 possessing the desired qualifications, but lacking in their ability to resist the 

 pathogene in question. 



The process of producing disease resistant types by hybridization is neces- 

 sarily slow because of the length of time that is required to isolate and fix the 

 desired type from the miscellaneous population that will appear as the result of 

 crossing. This diversity of the resulting population, while it constitutes a 

 hindrance to rapid progress, is one of the factors in favor of the hybridization 

 method of plant improvement in that the diverse population obtained affords a 

 good opportunity of isolating a plant possessing the maximum of desirable 

 qualities. 



A few examples will suffice to illustrate the work that is being done, mainly 

 by our plant pathologists, in the production of resistant strains by the isolation 

 of resistant individuals from commercial varieties. Blinn, (9) by selection 

 within commercial varieties, was able to isolate a cantaloupe resistant to rust. 

 Hansen (10) has secured by selection a type of sand cherry resistant to mildew. 



Figure 2.— The condition of the roots of four varieties of beans (hffering in their resistaJice to the 



(iry rot organism. 



Shamel and Cobey (11) o]:)tained a strain of tobacco resistant to wilt by one 

 year's selection. Bain et al. (12) selected a strain of Red Clover apparently 

 resistant to anthracnose. Norton (13) found that the tomato varieties Stone 

 and Stirling Castle possessed considerable resistance to the causal organism Oi" 

 leaf mold. Jones (14) developed a strain of cabbage possessing resistance to 

 yellows. Barrus (15) reports a strain of beans, obtained by a grower from an 

 individual plant selection, which is resistant to both strains of the bean anth- 

 racnose fungus. 



The possibilities of the slower and more difficult method of securing disease 

 resistant plants by means of hybridization, will be dealt with somewhat more 

 fully. In this connection the work done in securing beans resistant to the causal 



