BUILDING UP RESISTANCE TO DISEASES IN BEANS 

 Donald Reddick 



The common field bean (Phaseolus vulgaris L.) as grown in New York 

 is subject to a number of diseases and insect pests (Bnrkholder and 

 Hawley, 1923). Two of the common and destructive diseases occurring 

 in the State are anthracnose (caused byColletotrichum lindemuthia.nwm. 

 I Sacc. & Magn.) Bri. & Cav.) and mosaic (cause not known). With the 

 work of Barrus (1911) it became known that there are two separate and 

 distinct races of the anthracnose fungus which morphologically are iden- 

 tical but which biologically are very different. These races were named 

 alpha and beta. From the practical standpoint, therefore, two separate 

 anthracnose diseases were shown to exist. After extended experimen- 

 tation, Barrus reported (1918) on the behavior of a large number of 

 varieties of beans when inoculated with these two races of Colletotrichum 

 and the plants placed in optimum conditions for infection and the de- 

 velopment of disease. Only two varieties of field beans were found to be 

 very highly resistant or practically immune for both races of the fungus. 

 These were Wells' Red Kidney and White Imperial. 



Subsequently, Burkholder (1923) reported a third race of Colleto- 

 trichum lindemuthianum which he named gamma and which has the 

 ability to infect, among other bean varieties, both Wells' Red Kidney 

 and White Imperial. The existence of the gamma race was not known 

 at the inception of the work to be reported below. 



Likewise the work of Reddick and Stewart (1918) has shown for the 

 mosaic disease that, of a large number of varieties tested, only one showed 

 complete immunity to the disease. This was a selection which was sub- 

 mitted for test by the late Professor Spragg, of the Michigan Agricul- 

 tural Experiment Station, and which he finally described (1921) under 

 the n^me Robust. This variety, like its progenitor Navy Pea, is suscep- 

 tible to Colletotrichum lindemuthianum, race alpha, is practically im- 

 mune to beta, and, fortunately for the outcome of this work, was found 

 by Burkholder (1923) to be immune to race gamma. 



*The work of Burkholder (1918) and of McRostie (1921) on bean 

 breeding tor disease resistance, which was in progress in 1917, was well 

 known to the writer. The progress of their work led strongly to the 

 belief that suitable hybridizations would lead to the development of 

 beans which would combine the resistance to anthracnose of each parent 

 and the immunity to mosaic of one. 



On the day (October 24, 1918) that Dr. Barrus terminated his inocu- 

 lation experiments with the variety White Imperial, from which he con- 



