RUST RESISTANCE IN WINTER- WHEAT VARIETIES. 15 



sceptible variety. The inoculation method used was described by 

 Melchers {28) and was a modification of the method proposed and 

 used by Kellerman {22) and Carleton (7) in their studies of cereal 

 and other rusts. This is a satisfactory method where the supply of 

 rust is limited, as there is little chance for loss of spores. The spore 

 supply was collected in a Petri dish and applied to the seedlings by 

 means of a flattened or a rounded needle. The leaves to be inocu- 

 lated were first thoroughly dampened by stroking them several 

 times between the fingers previously moistened in water. Tap 

 water was used with satisfactory results, although Melhus and Dur- 

 rell {32) have shown that tap water may have a toxic effect on the 

 germination of certain kinds of rust spores. 



In the studies in the greenhouse the seedlings were grown in 24-inch 

 pots, illustrated in figure 2. Fifteen pots, each containing 2 seed- 

 lings, or 30 seedlings in all, constituted one series of each variety. 



Fig. 2. — Seedlings grown to determine rust resistance of wheat varieties under greenhouse conditions. 

 Pots 1 and 2 contain seedlings of a susceptible variety used as a check; Nos. 3 to 6 contain seedluigs of 

 P1068. Each of the two seedlings in each pot is trimmed to a single leaf blade which is inoculated. 



In most cases it was not necessary to inoculate more than one series 

 of plants, but if the results were at all doubtful a second series was 

 inoculated. Hundreds of inoculations were made on seedlings of 

 Kanred, P1066, and P1068. Two to four seedlings of Improved 

 Turkey (Kansas No. 2382) were used as checks for each series. 



After inoculation, the seedlings were kept in damp chambers for 

 48 hours, after which they were removed and placed on the green- 

 house bench. Bell jars were first used, but these proved impracti- 

 cable. An inexpensive and effective damp chamber, shown in 

 Plate VII, was devised. It consisted of a galvanized-iron washtub 

 with a pane of glass for a cover." 



About one-quarter of an inch of water was placed in the bottom of 

 each chamber, to keep the air saturated. The chambers were kept 

 in the shade, so as to maintain a temperature of 50° to 70° F. In 

 warm weather, a spray of water was directed upon the damp cham- 

 bers to reduce the temperatures. Difficulty was experienced during 



9 Cylinders made of galvanized iron (without permanent top or bottom), with a diameter of 15 inches 

 and a height of 12 inches, have been used more recently. A removable piece of glass is used for a top. If 

 these cylinders stand on damp sand, sufficient moisture is supplied to keep the chamber saturated, and 

 the potted seedlings do not stand in water. Damp chambers of this type have proved very satisfactory. 



