REPORT OF THE SOCIETY 77 



strains of a large number of bean varieties demonstrated. For purposes of 

 discussion the strains will be alluded to as Strain A. and Strain B. Unfor- 

 tunately very few of our common field or garden varieties of beans are resistant 

 to both of these strains. A considerable number, particularly of our garden 

 beans, are susceptible to both strains of the pathcygene. The remaining varie- 

 ties are either susceptible to Strain A. and resistant to Strain B. or vice versa. 

 This condition of affairs has been both a detriment and an aid in the securing 

 of resistant types. The fact of the existence of two strains of the causal organ- 

 ism has decreased the chances of securing by selection individuals resistant to 

 both of these strains. This same fact was, however, an advantage in that it 

 presented the possibility of hybridizing a desirable variety resistant to Strain A. 

 with a desirable variety resistant to Strain B., and isolating from the offspring 

 strains resistant to both of these strains. This latter possibility was of part- 

 icular advantage in that the two types of field beans that were resistant to both 

 Strain A. and Strain B. each possessed the disadvantage of being a late maturing 

 variety. One of these varieties also had a colored seed and was in addition 

 very susceptible to bacterial blight. 



A type of White Marrow bean resistant to Strain A. was crossed with a 

 white pea bean type resistant to Strain B. The first generation plants of this 

 cross were resistant to both strains of the fungus and the second generation, 

 when inoculated with a mixture of both strains of the fungus, gave resistant and 

 susceptible plants in the proportion of nine resistant to seven susceptible. One 

 ninth of these resistant plants bred true for this character. The remaining 

 eight-ninths when grown to the third generation and re-inoculated gave a pro- 

 portion of plants that continued to breed true for resistance to both strains in 

 subsequent generations. Of the susceptible class three-sevenths were resistant 

 to Strain A, but susceptible to strain B., three sevenths resistant to Strain B, 

 but susceptible to Strain A and the remaining one-seventh susceptible to both 

 strains of the causal organism. Thus we see that by crossing the two varieties 

 of beans mentioned it was possible to isolate not only strains resistant to, but 

 also strains susceptible to, both strains of the anthracnose fungus, without 

 recource to either a homozygous resistant or a homozygous susceptible variety. 



The enormous losses entailed annually from diseases apparently beyond 

 our control by artificial means as well as the labor and expense of our sprayings 

 and seed treatments, point to the necessity of furthering as rapidly as possible 

 natural means of control. Each year we patiently submit to losses from various 

 diseases of our cereal and horticultural crops when such losses could be prevented 

 by intelligent breeding of resistant varieties. 



The need of the hour, then, is the closer co-operation between the plant 

 pathologists and the plant breeders of the country, investigators with special 

 training in pathological plant breeding, and finally sufficient moral and financial 

 support to carry this work forward to a successful termination. 



