xxii Report of the Dean 



The bean-disease expert employed in the investigation had had a previous 

 experience of two years in studying bean diseases. He had already estab- 

 lished the fact that dry root rot is caused by a parasitic fungus and that 

 it is one of the very important diseases of the bean, and had determined 

 from extensive experimentation that none of the common methods of soil 

 disinfection or sanitation are of value in its control. It seemed that the 

 method of control of this and of some other bean diseases lay in the pos- 

 sibility of finding plants resistant to disease, and in the improvement of 

 such strains either by selection or by hybridization. The disease expert 

 and the breeder, therefore, have joined forces in work of this nature. 



A few bean plants of a non-commercial variety have been discovered 

 which are resistant to the dry root rot. These have been crossed with the 

 commercial white marrow bean, and the second generation was grown 

 in disease-infested soil this season. 



One hundred and thirty varieties of beans and nearly five hundred 

 plant selections, made the preceding year, were tested in disease-infested 

 soil to determine their relative value and their susceptibility to the dry 

 root rot disease. Records were made on all, and some were found which 

 apparently resisted the disease. . 



Numerous crosses of different bean varieties were made with the idea 

 of isolating a good commercial type resistant to root rot. Seed from these 

 crosses is being grown in the greenhouse so that the results can be tested 

 in the field in 191S. 



About one thousand plants of a cross between the anthracnose-resistant 

 red kidney bean and the white marrow bean were grown this season, 

 in order to secure a white marrow which would not be susceptible to 

 anthracnose. 



Connected with the above lines of experimentation is a great amount 

 of technical detail that need not be mentioned here. In addition to the 

 above work, the disease expert has studied two other root diseases of the 

 bean, black root rot and Rhizoctonia root rot, and has found that they 

 are of less economic importance than the dry root rot. He has also obtained 

 records for a study of the relation of weather conditions to the prevalence 

 of root rot, and is now engaged in a study of the relation of soil moisture 

 and soil temperature to infection of the bean plant by the fungus causing 

 dry root rot. 



The plant breeder has taken records on over five hundred rows (ten 

 feet each) of beans selected for increased yield. Extensive selections in 

 various bean sections have been made. A great number of exceptional 

 plants have been found which give promise for improvement in yield 

 and in uniformity. Additional selections were made also for disease- 

 resistant ])lants. 



