The Dry Root-Rot of the Bean 1031 



lead to the belief that the strain is closely related to the Blue Pod Medium. 

 The seeds are smaller and flatter than in the Marrow, but seldom are 

 they the shape of those of the Burlingame. During the early part of 

 the season these plants are difficult to distinguish from the Marrow, but 

 a few weeks before harvest time they may readily be distinguished from 

 the other varieties. This is due practically to the fact that the resist- 

 ance to root-rot is remarkably noticeable (Plate LVI, 3). The Flat Mar- 

 row cannot be grown commercially in New York State, however, because 

 of several objectionable characters. It is later than the White Marrow 

 and, altho very productive, it frequently is injured by frosts. Another 

 undesirable character is the length of its podding season. When the first 

 pods are ripe the later ones are still small and green. Nevertheless its 

 character of resistance to root-rot makes it a valuable bean. 



It has been shown by the writer (1918) that resistance to anthracnose 

 in beans can be transferred from one variety to another by hybridization. 

 It was therefore hoped that by crossing the Flat Marrow with any of 

 the common commercial varieties of bean, strains of the latter might 

 be obtained resistant to the dry root-rot. In making selections among 

 the Flat Marrow for parent stock, other characteristics besides disease 

 resistance were considered. These were, earliness of maturing, and 

 tendencies toward a White Marrow or a Medium type of bean. In 1915 

 only nineteen individuals were selected. The progeny of these were tested 

 for resistance in the greenhouse during the following winter and in the field 

 during the seasons of 1916 and 1917. Only seven strains were discarded. 

 Numerous crosses have been made by the writer between the Flat Marrow 

 and the White Marrow, and more recently E. W. Lindstrom and G. P. 

 McRostie have hybridized the resistant type with a number of other 

 commercial varieties of dry shell beans. The F 2 generation of all the 

 first hybrids have been grown, and part of the F 3 generation. These 

 have exhibited a very complex segregation, and it is the opinion of the 

 writer that the character of disease resistance in this case is not governed 

 by simple factors. 



As yet no White Marrow strain has been isolated resistant to the dry 

 root-rot. Insufficient knowledge concerning the genetical behavior of 

 the characters of resistance to this disease, however, renders it impossible 

 to state with certainty what may be done. Nevertheless it is hoped 

 that desirable types possessing root-rot resistance may be obtained from 

 the above crosses. 



