10 PROTECTION OF PLANTS — 1923-24 



It may be noted however, that the chief advance so far has been in the solving 

 of many of the fundamental problems in genetics, and in the isolating of the 

 numerous biologic strains which constitute Puccinia graminis tritici. One 

 cannot refer to this important work without mentioning the names of Eriksson 

 Biffin, Stakman, Pole Evans and ]\Ielchers. One of the most promising 

 reports, in that it offers scientific evidence as to the possibility of producing 

 varieties of common wheat resistant to a large number of biologic forms of 

 stem rust, is that of Aamodt (1), in the Journal of Agricultural Science on the 

 "Inheritance of growth habit and resistance to stem rust in a cross between 

 two varieties of common wheat. He reports "That the resistance and sus- 

 ceptibility of the host to several different forms of rust, arc inherited as a 

 single genetic factor." 



The work that has been done in the breeding and selection of beans 

 resistant to anthracnose illustrates the complications of such a problem due 

 to the existence of different biologic strains of the fungus. In 1911 M. F. 

 Barrus, of Cornell, proved that there were at least two distinct binologic strain 

 of Colletotrichum lindemuthianum in New York State which he designated 

 as alpha and beta. Nearly all the varieties of beans tested by Barrus were 

 susceptible to one or the other of these strains. A few however, were resistant 

 to both, among these were Wells Red Kidney and White Imperial (2). From 

 these two varieties Burkeholder, McCrostie and Reddick developed several 

 other commercial varieties of beans resistant to anthracnose in New York. 

 Burkeholder later showed the existence in New York of a third biologic strain 

 which he called the gamma strain, and demonstrated that neither Wells Red 

 Kedney, nor White Imperial were resistant to it. In fact Wells Red Kidney, 

 which hitherto had been considered the most resistant variety of all to the 

 anthracnose fungus was especially susceptible to this third biologic strain (3). 

 J. B. Leach (1923) reports that in Minnesota there are at least eight distinct 

 biologic strains of Colletotrichum lindemuthianum (4). The piesence of 

 these distinct biologic strains in different localities complicates the problem 

 of the breeding of anthracnose resistant varieties. It would appear that the 

 biologic strains in any locality must first be isolated and varieties bred and 

 selected in relation to them. Probably the most practical progress that 

 has been made in the production of disease free beans is the work of Reddick 

 and Stewart in proving that the robust bean is immune to the mosaic disease. 

 Burkeholder states that the growing of pea beans in New York State had been 

 practically discontinued due to the mosaic disease, but as a result of the intro- 



1. Aamodt, Olaf. S. Jour. Art. Res. 24: 457-469, 1923. 



2. Barn,«, M. F. Phytopathology 1: 190-19.5, 1911. 



3. Burkeholder, W. H. Phytopathology 13 316-323, 1923. 



4. Leach, J. G. Minnesota Agr. Expt. Sta. Tech. Bui. 14, Mch 1923. 



