4 BULLETIjST 1046, U. S. DEPARTMENT OF AGEICULTUEE. 



NURSERY EXPERIMENTS. 



METHODS AND MATERIALS. 



Because of the infrequent occurrence of natural epidemics of stem 

 rust under Kansas conditions/ it was necessary to study varietal 

 resistance in a rust nursery (PL I, figures 1 and 2), following the gen- 

 eral plan suggested by Johnson (20). This rust nursery was located 

 near Manhattan, Kans., on land which is low and slopes slightly 

 toward the south and west. Along the south side of the nursery is 

 a hedge of common barberry bushes (PI. I, fig. 2). A large drainage 

 ditch on the south side carried off the surplus water. Because of 

 the likelihood of frequent heavy rains during the crop season, the 

 rust nursery was sown in slightly elevated plats, separated by de- 

 pressed alleys, which received the surplus water and carried it into 

 the main ditch. The rust nursery has been sown in various ways. 

 At first a plat 1 rod square was used for each variety, but it was 

 found impossible to produce severe epidemics of stem rust on large 

 areas under Kansas conditions. The plats, therefore, were reduced 

 to a single rod row and in 1915 to 5-foot nursery rows spaced 10 

 inches apart. The seeds are sown 3 inches apart in the row. A 

 small hand plow was used for opening a furrow and a seeding board 

 with notches at regular intervals served to obtain uniformity in 

 spacing the seed. 



The spring varieties generally were sown during the last week in 

 March or the first week in April in rows close to the winter-wheat 

 rust nursery. 



The rust used in these experiments up to and including 1917 was 

 obtained from the Minnesota Agricultural Experiment Station. In 

 1914, 1915, and 1916 the urediniospores came from greenhouse cul- 

 tures of Puccinia graminis tritici, but in the fall of 1917 cultures 

 were used from rusted wheat plants obtained in the field. These 

 were found later to be a new strain of stem rust (30). The stock 

 cultures of rust which were used in these field experiments were 

 cultured on Improved Turkey (Kansas No. 2382), a variety which 

 has been found in these experiments to be very susceptible to stem 

 rust. When the leaves produced uredinia which were sporulating 

 abundantly they were used in one of two ways: (1) The leaves 

 were clipped from the plants, placed in a iew quarts of water, the 

 urediniospores removed, and the hquid used as a spray on the wheat 

 plants in the rust nursery, or (2) the potted wheat plants bearing 

 uredinia were used as centers of infection in the nursery, 



6 The only natural epidemic known to the writers occurred in 1904. In 1915 and 1916 stem rust was very 

 prevalent in many fields in Kansas and in some instances there was an appreciable loss. In 1919 stem rust 

 was uniformly present in eastern and central Kansas, and although it was difficult to estimate the actual 

 injury caused by stem rust it was one of several factors which reduced the yield and quality of wheat. 



